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Authors: Junhao Li, Yan Huang, Xiaosong Yu, Qiqi Wu, Xiaxia Man, Zhihong Diao, Huang You, Jinbo Shen and Yi Cai.
Journal of Agricultural and Food Chemistry (2024)
Abstract: "The CLE (CLAVATA3/Embryo Surrounding Region-related) family, a group of peptides with hormone-like features, plays a pivotal role in plant growth, development, and adaptation to stress. Through homology-based blast analysis of 32 Arabidopsis thaliana CLE peptide sequences, we have identified 5, 14, and 10 CLE family members in Nicotiana tabacum, Capsicum annuum, and Solanum melongena, respectively. Chemical synthesis and functional assays of the peptides led to the discovery that NtCLE3 substantially enhances the drought resistance of these three Solanaceae crops. Our transcriptome, RT-qPCR, and antioxidant enzyme activity data showed that NtCLE3 increased antioxidant capacity and ABA synthesis in tobacco. Moreover, the recombinant protein RPNtCLE3, composed of 6*NtCLE3, preserved the capacity to foster drought resilience and proved to be a promising drought resistance regulator, which presents a more favorable alternative for field applications compared to ABA which degrades rapidly under sunlight exposure. This research unveils the prospective utility of NtCLE3 in enhancing drought tolerance in Solanaceae crops and provides new ideas for the development of novel bioregulators aimed at mitigating drought stress."
Authors: Xiaobo Song, Naifu Zhou, Yingying Chang, Junpei Zhang and Dong Pei.
Trees (2024)
Abstract: "Plant grafting involves naturally or intentionally merging distinct plant parts to form a single organism. Although it is a common horticultural practice used to improve the yield, quality, and resistance of horticultural crops and study the long-distance transport of molecules, the underlying mechanism of graft union formation (GUF) remains poorly understood. In this study, we optimized the in situ analysis method for plant hormones and explored the spatial and temporal distribution of endogenous hormones (IAA, ABA, and ZR) during walnut GUF. The results demonstrated that changes in endogenous IAA and ZR levels in the graft union were consistent, with an increase during the rapid proliferation phase of callus tissue and enrichment in the cambium and cells of the grafting interface. As callus tissue entered the differentiation stage, endogenous IAA and ZR levels rapidly decreased and were mainly distributed in the callus tissue. Conversely, the level and distribution of endogenous ABA showed no significant changes during the rapid proliferation phase of callus tissue. However, they increased rapidly after entering the differentiation stage, mainly in the scion cambium and callus tissue. We also observed "S"-shaped, “M”-shaped, and “N”-shaped trends in the dynamic changes of IAA/ABA, IAA/ZR, and ZR/ABA ratios, respectively. Based on these results, we propose a spatial and temporal distribution model of endogenous hormones during walnut GUF. This provides a foundation for further investigation into the molecular mechanisms of hormone-mediated GUF in walnut and other woody plants."
Authors: Xueyuan Han, Chi Shen, Fangfang He, Yuxin Liu and Zisheng Luo.
Postharvest Biology and Technology (2024)
Highlights: • Both ethylene (ET) and ABA promoted the aroma recovery of cold-stored kiwifruit. • The pathways related to aroma synthesis were influenced by ABA or ET treatment. • ABA and ET may have different regulatory tendencies in kiwifruit aroma recovery.
Abstract: "Cold storage (CS) combined with preservative treatment is widely employed to effectively extend the storage duration of kiwifruit. Nevertheless, the olfactory quality of cold-stored kiwifruit tends to deteriorate during the post-ripening phase. In this study, abscisic acid (ABA) or ethylene (ET) was supplementary administered to cold-stored kiwifruit (CS combined with a preservative 1-MCP treatment) prior to transferring from CS, with the aim of examining the impact of ABA and ET on aroma restitution during the post-ripening period (designated as MCP+ABA and MCP+ET, respectively). The results revealed that the firmness of the MCP+ABA and MCP+ET treatments remained higher than that of the control (CK, without 1-MCP treatment) throughout the post-ripening phase, both of which moreover promoted the accumulation of soluble solids and titratable acids in kiwifruit comparing to 1-MCP group. The ethylene production and respiration rate of the fruit treated with MCP+ET and MCP+ABA fell within the intermediate range between the 1-MCP and CK groups. Compared to the 1-MCP group, both MCP+ABA and MCP+ET treatments significantly improved the accumulation of volatile components, particularly aldehydes and ketones during the early stage, and esters during the later stage of post-ripening. The activity analysis of pivotal enzymes involved in aroma biosynthesis revealed that ABA stimulated an increase in alcohol dehydrogenase (ADH) activity, while ET had a notable inducing effect on alcohol acyltransferase (AAT) and hydroperoxide lyase (HPL) activities. Furthermore, transcriptomic sequencing analysis revealed differential induction of gene expression in the pathways associated with aroma biosynthesis by ABA and ET, wherein they significantly upregulated distinct genes. Additionally, principal component analysis provided a more intuitive depiction that ABA and ET appeared to enhance the restoration of aroma in cold-stored kiwifruit by activating diverse metabolic pathways or key genes. In a comprehensive assessment, the present study postulates that both ABA and ET exert restorative effects on the aroma of cold-stored kiwifruit, thus offering theoretical support for aroma restitution technology in cold-stored fruit."
Authors: Alice Robustelli Test, Giorgio Perrella, Sara Colanero, Beatrice Landoni, Aldo Sutti, Paolo Korwin Krukowski, Elisa Vellutini, Giulia Castorina, Massimo Galbiati, Damiano Martignago, Eirini Kaiserli, Chiara Tonelli and Lucio Conti.
bioRxiv (2024)
Highlight: ABA and GIGANTEA signalling promote FLOWERING LOCUS T (FT) transcriptional activation by regulating the binding of the transcription factor CONSTANS to the proximal FT promoter.
Abstract: "Plants align flowering with optimal seasonal conditions to increase reproductive success. This process depends on modulating signalling pathways that respond to diverse environmental and hormonal inputs, thereby regulating the transition to flowering at the shoot apical meristem. In Arabidopsis, long-day photoperiods (LDs) stimulate the transcription of FLOWERING LOCUS T (FT), encoding the main florigenic signal. FT activation is mediated by the transcriptional regulator CONSTANS (CO), which binds to the CO responsive elements (COREs) located in the proximal FT promoter region. The phytohormone abscisic acid also (ABA) contributes to FT activation together with GIGANTEA (GI) to regulate drought escape (DE). Whether CO is a target of ABA and GI actions for the regulation of FT is, however, unknown. Here we report that ABA and its signalling components promote CO recruitment to the COREs, without causing clear effects on the diel pattern of CO protein accumulation. We also found that GI promotes CO recruitment to the COREs region, and that CO recruitment is required for the accumulation of RNAPol II at the TRANSCRIPTION START SITE of FT. Finally, we show that GI and ABA signalling pathways are largely epistatic in the control of flowering time, suggesting their involvement in the same molecular process. Taken together, these observations suggest that varying water deficit conditions modulate CO recruitment and FT expression, thus dictating DE strategies in Arabidopsis."
Authors: Nidhi Kandhol, Sangeeta Pandey, Vijay Pratap Singh, Luis Herrera-Estrella, Lam-Son Phan Tran and Durgesh Kumar Tripathi.
Research (2024)
Abstract: "The menace of drought has persistently loomed over global crop production, posing a significant threat to agricultural sustainability. Research on drought stress highlights the significant role of the phytohormone abscisic acid (ABA) in orchestrating plant responses to drought conditions. ABA regulates various drought/dehydration-responsive genes, initiates stomatal closure, and influences cellular responses to drought stress. Additionally, plants employ a phosphate starvation response (PSR) mechanism to manage phosphate (Pi) deficiency, with ABA playing a role in its regulation. However, despite intensive research in these fields, the precise connection among PSRs, drought stress, and ABA signalling still needs to be determined. The recent study by Nagatoshi and colleagues (2023) demonstrates that PSR-related gene induction occurs before the induction of ABA-responsive genes under progressive mild drought. Mild drought decreases Pi uptake and contents in plants, triggering PSRs, which play an important role in plant growth during mild drought. Both ABA-responsive and PSR-related gene expression could indicate plant perception of external moisture conditions. Thus, integrating the information regarding their associated gene expression with soil moisture contents and thermographic data can enable timely irrigation optimization to mitigate the effect of drought on crop productivity."
Authors: Arnau Rovira, Nil Veciana, Aina Basté-Miquel, Martí Quevedo, Antonella Locascio, Lynne Yenush, Gabriela Toledo-Ortiz, Pablo Leivar and Elena Monte.
Nature Communications (2024)
Editor's view: Stomata function is essential for photosynthesis and the global carbon and oxygen cycles. Here, the authors report the regulatory framework that establishes rhythmic pore movements to prevent water loss at night and allow CO2 uptake during the day.
Abstract: "Stomata govern the gaseous exchange between the leaf and the external atmosphere, and their function is essential for photosynthesis and the global carbon and oxygen cycles. Rhythmic stomata movements in daily dark/light cycles prevent water loss at night and allow CO2 uptake during the day. How the actors involved are transcriptionally regulated and how this might contribute to rhythmicity is largely unknown. Here, we show that morning stomata opening depends on the previous night period. The transcription factors PHYTOCHROME-INTERACTING FACTORS (PIFs) accumulate at the end of the night and directly induce the guard cell-specific K+ channel KAT1. Remarkably, PIFs and KAT1 are required for blue light-induced stomata opening. Together, our data establish a molecular framework for daily rhythmic stomatal movements under well-watered conditions, whereby PIFs are required for accumulation of KAT1 at night, which upon activation by blue light in the morning leads to the K+ intake driving stomata opening."
Authors: Qian Li, Juan Wang, Zhaonan Yin, Yingfang Pan, Wei Mao, Liangyu Peng, Xinyue Guo, Bao Li and Ping Leng.
The Plant Journal (2024)
Significance Statement: SlPP2C2 regulates tomato development by integrating ABA and auxin signals through interaction with FZY/SAUR. This finding extends our knowledge of ABA signal cross talk in regulation of tomato development.
Abstract: "Abscisic acid (ABA) signaling interacts frequently with auxin signaling when it regulates plant development, affecting multiple physiological processes; however, to the best of our knowledge, their interaction during tomato development has not yet been reported. Here, we found that type 2C protein phosphatase (SlPP2C2) interacts with both flavin monooxygenase FZY, an indole-3-acetic acid (IAA) biosynthetic enzyme, and small auxin upregulated RNA (SAUR) of an IAA signaling protein and regulates their activity, thereby affecting the expression of IAA-responsive genes. The expression level of SlPP2C2 was increased by exogenous ABA, IAA, NaCl, or dehydration treatment of fruits, leaves, and seeds, and it decreased in imbibed seeds. Manipulating SlPP2C2 with overexpression, RNA interference, and CRISPR/Cas9-mediated genome editing resulted in pleiotropic changes, such as morphological changes in leaves, stem trichomes, floral organs and fruits, accompanied by alterations in IAA and ABA levels. Furthermore, the RNA-seq analysis indicated that SlPP2C2 regulates the expression of auxin-/IAA-responsive genes in different tissues of tomato. The results demonstrate that SlPP2C2-mediated ABA signaling regulates the development of both vegetative and reproductive organs via interaction with FZY/SAUR, which integrates the cross-talk of ABA and auxin signals during development and affects the expressions of development-related genes in tomato."
Authors: Nathalie Kuhn, Macarena Arellano, Claudio Ponce, Christian Hodar, Francisco Correa, Salvatore Multari, Stefan Martens, Esther Carrera, José Manuel Donoso and Lee A. Meisel
Journal of Plant Growth Regulation (2024)
Abstract: "Abscisic acid (ABA) is a plant hormone that plays a key role in the ripening process of non-climacteric fruits, triggering pigment production, fruit softening, and sugar accumulation. Transcriptional studies show that ABA modifies the expression of several ripening-related genes, but epigenetic effects of ABA during this process are lacking. Therefore, this work aimed to perform transcriptomic and DNA methylation analyses of fruit samples treated with ABA during the fruit ripening process in the non-climacteric sweet cherry model. RNA-seq analyses revealed an overrepresentation of transcripts annotated in functional categories related to ABA response, secondary metabolism, and sugar synthesis during fruit ripening. In contrast, Whole Genome Bisulfite Sequencing (WGBS) analyses revealed DNA hypomethylation in the 5′UTR region of genes related to carotene catabolism. Transcriptional and epigenetic regulation of genes encoding xyloglucan enzymes, associated with cell wall modifications, were also detected. ABA treatment enhanced fruit color development and the accumulation of ripening markers, including carotenoids and several anthocyanins. Gene Ontology analysis in the RNA-seq of ABA-treated fruits revealed expression variations in genes encoding members of the Aux/IAA and ARF families. In the WGBS analysis, genes encoding enzymes for cytokinin biosynthesis had differential DNA methylation after the ABA treatment. Our work identified ABA-modulated factors at the genetic and epigenetic levels, suggesting complex hormone networks controlling non-climacteric sweet cherry fruit ripening."
Authors: Pierre Gautrat, Sanne E. A. Matton, Lisa Oskam, Siddhant S. Shetty, Kyra J. van der Velde and Ronald Pierik.
Journal of Experimental Botany (2024)
Abstract: "Plants growing in dense vegetation stands need to flexibly position their photosynthetic organs to ensure optimal light capture in a competitive environment. They do so through a suite of developmental responses referred to as the shade avoidance syndrome. Belowground, root development is also adjusted in response to aboveground neighbour proximity. Canopies are dynamic and complex environments with heterogeneous light cues in the far-red, red, blue and UV spectrum, which can be perceived with photoreceptors by spatially separated plant tissues. Molecular regulation of plant architecture adjustment via PHYTOCHROME-INTERACTING FACTOR (PIF) transcription factors and growth-related hormones such as auxin, gibberellic acid, brassinosteroids and abscisic acid were historically studied without much attention to spatial or tissue-specific context. Recent developments and technologies have, however, sparked strong interest in spatially explicit understanding of shade avoidance regulation. Other environmental factors such as temperature and nutrient availability interact with the molecular shade avoidance regulation network, often depending on the spatial location of the signals, and the responding organs. Here, we aim to review recent advances in how plants respond to heterogenous light cues and integrate these with other environmental signals."
Authors: L. Wang, E. Brouard, D. Prodhomme, G. Hilbert, C. Renaud, J.-P. Petit, E. Edwards, A. Betts, S. Delrot, N. Ollat, S. Guillaumie, Z.W. Dai and E. Gomès.
Acta Horticulturae (2024)
Abstract: "High temperatures (HT) usually increase berry sugar concentrations, while reducing organic acids and anthocyanin levels, thereby modifying wine quality and character. Viticultural practices such as leaf-to-fruit ratio (L/F) manipulation, combined with application of abscisic acid (ABA) can potentially be used to mitigate HT effects and adjust berry composition. In the present work, after confirming the effects of LF and ABA applications on berry composition over a six-year period, we studied the mechanisms underlying these effects on berry composition and ABA metabolism in 'Cabernet Sauvignon' fruiting-cuttings (i.e., Mullins' vines). Reducing L/F significantly reduced berry sugar and anthocyanin contents, and slightly increased total organic acid content. ABA application increased anthocyanin concentration, and partially restored the coupling between sugar and anthocyanin accumulation under low L/Fs, without affecting the sugar/organic acid ratio. Several transcripts of the anthocyanin biosynthesis pathway (CHS2, CHS3, CHI, F3H, DFR, LODX, UFGT, MybA1 and MybA2) were less abundant under low L/F ratio, whereas some transcripts (CHI, F3H, F35H, LODX, UFGT, MybA1 and MybA2) were upregulated after ABA treatment. ABA treatment had little effect on the transcript abundance of genes related to sugar accumulation, except SWEET10 in 12L plants. Carbon source limitation to clusters also had little effect on ABA biosynthetic genes, but decreased berry ABA concentration. In conclusion, our results show that ABA and sugar signaling synergistically interact to regulate the expression of anthocyanin biosynthetic genes and increase anthocyanin accumulation. Thus, combining L/F ratio manipulation with ABA applications may offer a fine-tuned way to reduce sugar concentration, while maintaining anthocyanin concentrations in grape berry, potentially offering a way to partially alleviate the warming effects of climate change."
Authors: Meiying Liu, Chaoran Wang, Hongliang Ji, Maoxiang Sun, Tongyu Liu, Jiahao Wang, Hui Cao and Qinggang Zhu.
Frontiers in Plant Science (2024)
Abstract: "In recent years, the ethylene-mediated ripening and softening of non-climacteric fruits have been widely mentioned. In this paper, recent research into the ethylene-mediated ripening and softening of non-climacteric fruits is summarized, including the involvement of ethylene biosynthesis and signal transduction. In addition, detailed studies on how ethylene interacts with other hormones to regulate the ripening and softening of non-climacteric fruits are also reviewed. These findings reveal that many regulators of ethylene biosynthesis and signal transduction are linked with the ripening and softening of non-climacteric fruits. Meanwhile, the perspectives of future research on the regulation of ethylene in non-climacteric fruit are also proposed. The overview of the progress of ethylene on the ripening and softening of non-climacteric fruit will aid in the identification and characterization of key genes associated with ethylene perception and signal transduction during non-climacteric fruit ripening and softening."
Authors: Estefanía Contreras, Elena Pastor-Mora, Mar Aylón-Rodríguez, Mar González-Ceballos, Miguel Ángel Delgado-Gutiérrez, Inmaculada Sánchez-Vicente, Óscar Lorenzo, Jesús Vicente- Carbajosa and Raquel Iglesias-Fernández.
bioRxiv (2024)
Abstract: "Autophagy is a cell recycling mechanism that degrades cytoplasmic components. Although classically considered a non-selective bulk degradation mechanism, autophagy also functions selectively. Here, we investigate the impact of autophagy on seed development by studying the autophagy-related (ATG) genes AtATG5 and AtATG7 in Arabidopsis, focusing on their role in ABA responses. Seeds of atg5 and atg7 mutants germinate significantly slower than Col-0, especially in the presence of ABA. Transcriptomic analyses comparing imbibed atg7 and Col-0 seeds reveal differences in gene expression associated with lipid storage and seed maturation ontology categories., Germinating seeds of atg mutants show histochemical alterations in the organisation of lipid droplets and protein storage vacuoles (PSV) in the emerging radicle. Notably, immunolocalization of ATG8 is observed in PSV in Col-0, but not in atg mutants. In the presence of ABA, approximately 10% of the transcriptome induced in atg7 and repressed in Col-0 has been reported to be under control of the transcription factors ABI3 and ABI5, master regulators of ABA signaling in the seed. Yeast-two hybrid assays confirmed their direct interaction with the autophagy machinery through ATG8. Interestingly, the decrease in ABI5 observed in Col-0 seeds after imbibition is delayed in atg mutants, which also show altered accumulation in developing seeds of the ABI5 homolog bZIP67 that regulates reserve biosynthesis. Taken together, our data highlight the relevance of autophagy in controlling seed reserve mobilisation, its impact on seed germination, and the perception of environmental signals through ABA responses that include a transcription factor decay mechanism."
Authors: Benjamin Hubert, Olivier Leprince and Julia Buitink.
Journal of Experimental Botany (2024)
Abstract: "To ensure their vital role in disseminating the species, dormant seeds have developed adaptive strategies to protect themselves against pathogens and predators. This is orchestrated through the synthesis of an array of constitutive defenses that are put in place in a developmentally regulated manner, which are the focus of this review. We summarize the defense activity and the nature of the molecules coming from the exudate of imbibing seeds that leak into its vicinity, also referred to as the spermosphere. As a second layer of protection, the dual role of the seed coat will be discussed; as a physical barrier and a multi-layered reservoir of defense compounds that are synthesized during seed development. Since imbibed dormant seeds can persist in the soil for extended times, we address the question if during this period, a constitutively regulated defense program is switched on to provide further protection, using the well-defined pathogenesis-related (PR) protein family. In addition, we review the hormonal and signaling pathways that might be involved in the interplay between dormancy and defense and point out questions that need further attention."
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Authors: Yakong Wang, Xiangyang Sun, Jun Peng, Fuguang Li, Faiza Ali and Zhi Wang.
Journal of Advanced Research (2024)
Highlights: • ROS, epigenetics, and hormones play crucial roles in regulating seed germination processes. • ROS regulates seed germination by influencing hormone levels through Ca2+, NO signaling, and MAPK cascade reaction. • ROS plays a role in seed germination through DNA methylation, chromatin remodeling, and protein post-translational modification. • Sophisticated feedback regulations between ROS, phytohormones, and epigenetic modifications determine seed germination.
Abstract: "Background -The whole life of a plant is regulated by complex environmental or hormonal signaling networks that control genomic stability, environmental signal transduction, and gene expression affecting plant development and viability. Seed germination, responsible for the transformation from seed to seedling, is a key initiation step in plant growth and is controlled by unique physiological and biochemical processes. It is continuously modulated by various factors including epigenetic modifications, hormone transport, ROS signaling, and interaction among them. ROS showed versatile crucial functions in seed germination including various physiological oxidations to nucleic acid, protein, lipid, or chromatin in the cytoplasm, cell wall, and nucleus. Aim of review - This review intends to provide novel insights into underlying mechanisms of seed germination especially associated with the ROS, and considers how these versatile regulatory mechanisms can be developed as useful tools for crop improvement. Key scientific concepts of review - We have summarized the generation and elimination of ROS during seed germination, with a specific focus on uncovering and understanding the mechanisms of seed germination at the level of phytohormones, ROS, and epigenetic switches, as well as the close connections between them. The findings exhibit that ROS plays multiple roles in regulating the ethylene, ABA, and GA homeostasis as well as the Ca2+ signaling, NO signaling, and MAPK cascade in seed germination via either the signal trigger or the oxidative modifier agent. Further, ROS shows the potential in the nuclear genome remodeling and some epigenetic modifiers function, although the detailed mechanisms are unclear in seed germination. We propose that ROS functions as a hub in the complex network regulating seed germination."
Authors: Han Wei, Xiao Wang, Kaitong Wang, Xun Tang, Ning Zhang and Huaijun Si.
Physiologia Plantarum (2024)
Abstract: "Plants often experience abiotic stress, which severely affects their growth. With the advent of global warming, drought stress has become a pivotal factor affecting crop yield and quality. Increasing numbers of studies have focused on elucidating the molecular mechanisms underlying plant responses to drought stress. As molecular switches, transcription factors (TFs) are key participants in drought-resistance regulatory networks in crops. TFs regulate the transcription of downstream genes and are regulated by various upstream regulatory factors. Therefore, understanding the mechanisms of action of TFs in regulating drought stress can help enhance the adaptive capacity of crops under drought conditions. In this review, we summarize the structural characteristics of several common TFs, their multiple drought-response pathways, and recently employed research strategies. We describe the application of new technologies such as analysis of stress granule dynamics and function, multi-omics data, gene editing, and molecular crosstalk between TFs in drought resistance. This review aims to familiarize readers with the regulatory network of TFs in drought resistance and to provide a reference for examining the molecular mechanisms of drought resistance in plants and improving agronomic traits."
Authors: Patricio Olmedo, Gerardo Núñez-Lillo, Excequel Ponce, Juan E. Alvaro, Jorge Baños, Esther Carrera, José Jorge González-Fernández, José Ignacio Hormaza, David Campos, Rosana Chirinos, Reinaldo Campos-Vargas, Bruno Giorgio Defilippi, Encarna Aguayo and Romina Pedreschi.
Food Science (2024)
Highlights: • 'Hass' avocados accumulated higher amounts of sucrose, mannoheptulose, and perseitol in both tissues. • 'Fuerte' avocados accumulated stearic acid, oleic acid, and linoleic acid in the exocarp. • Cultivars presented differences in amino acid and carbohydrate metabolisms. • 'Hass' avocado exocarp showed higher abscisic acid and salicylic acid content. • Cytokinins, trans-zeatin and dihydrozeatin were found accumulated in 'Fuerte' skins.
Abstract: "Color development in avocado fruits is a complex mechanism influenced by several factors. To understand this process, a comparative analysis was conducted between fruits of 'Fuerte' and 'Hass' avocado cultivars using metabolomic approaches. Pigment content in the exocarp differs between cultivars, accumulating anthocyanins in 'Hass' avocado. Carbohydrate abundance differed at ready-to-eat stage showing that 'Hass' accumulated higher amounts of sucrose, mannoheptulose, and perseitol than ‘Fuerte’ in both tissues. Higher amounts of fatty acids were observed in both tissues of 'Fuerte'. Polar metabolites indicated differences in amino acid and carbohydrate metabolisms between cultivars. Hormone analysis suggested that abscisic acid is involved in pigment biosynthesis. These findings showed that hormone and primary metabolites cross-talk plays an important role in color development in the exocarp and in the softening in the mesocarp of ‘Hass', opening new perspectives about this metabolic interplay and its relation to the development of the exocarp-mesocarp synchronization during ripening."
Authors: Xuexue Chen, Jiahui Gao and Yuanyue Shen.
The Plant Journal (2024)
Significance Statement: We unravel a novel abscisic acid signaling transduction pathway in sugar transport via “FaRIPK1-FaTCP7-FaSTP13/FaSPT,” which channels to strawberry fruit ripening.
Abstract: "Strawberry is considered as a model plant for studying the ripening of abscisic acid (ABA)-regulated non-climacteric fruits, a process in which sugar plays a fundamental role, while how ABA regulates sugar accumulation remains unclear. This study provides a direct line of physiological, biochemical, and molecular evidence that ABA signaling regulates sugar accumulation via the FaRIPK1-FaTCP7-FaSTP13/FaSPT signaling pathway. Herein, FaRIPK1, a red-initial protein kinase 1 previously identified in strawberry fruit, not only interacted with the transcription factor FaTCP7 (TEOSINTE BRANCHEN 1, CYCLOIDEA, and PCF) but also phosphorylated the critical Ser89 and Thr93 sites of FaTCP7, which negatively regulated strawberry fruit ripening, as evidenced by the transient overexpression (OE) and virus-induced gene silencing transgenic system. Furthermore, the DAP-seq experiments revealed that FvTCP7 bound the motif “GTGG CCCNC” in the promoters of two sugar transporter genes, FaSTP13 (sugar transport protein 13) and FaSPT (sugar phosphate/phosphate translocator), inhibiting their transcription activities as determined by the electrophoretic mobility shift assay, yeast one-hybrid, and dual-luciferase reporter assays. The downregulated FaSTP13 and FaSPT transcripts in the FaTCP7-OE fruit resulted in a reduction in soluble sugar content. Consistently, the yeast absorption test revealed that the two transporters had hexose transport activity. Especially, the phosphorylation-inhibited binding of FaTCP7 to the promoters of FaSTP13 and FaSPT could result in the release of their transcriptional activities. In addition, the phosphomimetic form FaTCP7S89D or FaTCP7T93D could rescue the phenotype of FaTCP7-OE fruits. Importantly, exogenous ABA treatment enhanced the FaRIPK1–FaTCP7 interaction. Overall, we found direct evidence that ABA signaling controls sugar accumulation during strawberry fruit ripening via the “FaRIPK1-FaTCP7-FaSTP13/FaSPT” module."
Authors: Fuli Huang, Mimi Sun, Zhijin Yao, Jing Zhou, Qian Bai, Xuexue Chen, Yun Huang and Yuanyue Shen.
Journal of Experimental Botany (2024)
Abstract: "Strawberry (Fragaria×ananassa) is a model plant for studying non-climacteric fruit ripening regulated by abscisic acid (ABA). However, the signaling of ABA in the regulation of fruit coloration is not fully understood. Here, a transcription factor FabHLH3 key to fruit coloration is identified by yeast two hybrid library screening using FaSnRK2.6 as a bait, an ABA core signaling component negative to ripening. Indeed, this interaction is also confirmed by firefly luciferase complementation assay and pull-down assay. RT-qPCR and Western blotting analysis confirm FabHLH3 is expressed ubiquitously in strawberry and stably during fruit development. Manipulating both FabHLH3 and FaSnRK2.6 expression by overexpression and interference demonstrates that FabHLH3 and FaSnRK2.6 promote and inhibit strawberry fruit coloration, respectively, using the marker gene FaUFGT, key to anthocyanin biosynthesis. FaSnRK2.6 can phosphorylate FabHLH3, which promotes FaUFGT expression by the directly binding to its promoter. The phosphorylation inhibits the binding of FabHLH3 to FaUFGT promoter, consequently suppressing FaUFGT expression. Altogether, FaSnRK2.6, a negative kinase in ripening, interacts with and phosphorylates FabHLH3 to suppress FaUFGT expression. With the increase of ABA content in strawberry fruit ripening, the expression of FaSnRK2.6 decreased, which released FabHLH3 transcription activity and enhanced FaUFGT expression, finally promoting the coloration. Thus, our findings fill a gap how FaSnRK2.6 negatively regulates strawberry fruit coloration and ripening by FabHLH3."
Authors: Aime Jaskolowski and Yves Poirier.
The Plant Journal (2024)
Significance Statement: When plants are subjected to a combination of biotic and abiotic stresses, the response to each individual stress is usually a poor predictor of the global response. Here, we show that when Arabidopsis plants are grown under phosphate deficiency, they increase the accumulation of the stress phytohormone abscisic acid, which in turn leads to higher susceptibility to infection by the necrotrophic fungus Botrytis cinerea, in part because of increased spore germination on the leaf surface.
Abstract: "Plants have evolved finely regulated defense systems to counter biotic and abiotic threats. In the natural environment, plants are typically challenged by simultaneous stresses and, amid such conditions, crosstalk between the activated signaling pathways becomes evident, ultimately altering the outcome of the defense response. As an example of combined biotic and abiotic stresses, inorganic phosphate (Pi) deficiency, common in natural and agricultural environments, can occur along with attack by the fungus Botrytis cinerea, a devastating necrotrophic generalist pathogen responsible for massive crop losses. We report that Pi deficiency in Arabidopsis thaliana increases its susceptibility to infection by B. cinerea by influencing the early stages of pathogen infection, namely spore adhesion and germination on the leaf surface. Remarkably, Pi-deficient plants are more susceptible to B. cinerea despite displaying the appropriate activation of the jasmonic acid and ethylene signaling pathways, as well as producing secondary defense metabolites and reactive oxygen species. Conversely, the callose deposition in response to B. cinerea infection is compromised under Pi-deficient conditions. The levels of abscisic acid (ABA) are increased in Pi-deficient plants, and the heightened susceptibility to B. cinerea observed under Pi deficiency can be reverted by blocking ABA biosynthesis. Furthermore, high level of leaf ABA induced by overexpression of NCED6 in Pi-sufficient plants also resulted in greater susceptibility to B. cinerea infection associated with increased spore adhesion and germination, and reduced callose deposition. Our findings reveal a link between the enhanced accumulation of ABA induced by Pi deficiency and an increased sensitivity to B. cinerea infection."
Authors: Zhenghua He, Pei Zhang, Haitao Jia, Shilong Zhang, Elsayed Nishawy, Xiaopeng Sun and Mingqiu Dai.
New Crops (2024)
Abstract: "Drought is a primary abiotic stress affecting crops, leading to plant stomatal closure, reduced photosynthetic capacity, and reduced yields or even harvest failure. Severe drought can adversely impact agricultural production, ecosystems, and socio-economic capacities. Recently, researchers have studied the regulatory mechanisms of crop drought resistance and cloned hundreds of genes via genetic and molecular approaches. However, a limited number of the cloned genes have been successfully employed in drought resistance breeding, suggesting that drought resistance regulation is too complex. More work must be done to fully understand the regulatory networks of drought responses to breed drought-resistant and high-yield crop varieties. This review outlines the current achievements in investigating crop drought responses, particularly regulation by phytohormones and regulation of genes at transcriptional, post-translational, and epigenetic levels in crop drought responses. Finally, we examine the problems and potential solutions in breeding crop drought resistance and propose strategies for crop drought resistance improvement."
Authors: Qingjun Xie, Danni Wang, Yuting Ding, Wenshuo Gao, Jinghang Li, Chuanwang Cao, Lili Sun, Zhongyuan Liu and Caiqiu Gao.
Science of the Total Environment (2024)
Highlights: • Various plant hormones play roles in the accumulation of Cd in T. hispida. • ABA and ethylene antagonistic regulation of Cd accumulation in T. hispida • ThDRE1A regulates Cd accumulation by regulating ThABAH2.5 and ThACCO3.1.
Abstract: "Tamarix hispida is highly tolerant to salt, drought and heavy metal stress and is a potential material for the remediation of cadmium (Cd)-contaminated soil under harsh conditions. In this study, T. hispida growth and chlorophyll content decreased, whereas flavonoid and carotenoid contents increased under long-term Cd stress (25 d). The aboveground components of T. hispida were collected for RNA-seq to investigate the mechanism of Cd accumulation. GO and KEGG enrichment analyses revealed that the differentially expressed genes (DEGs) were significantly enriched in plant hormone-related pathways. Exogenous hormone treatment and determination of Cd2+ levels showed that ethylene (ETH) and abscisic acid (ABA) antagonists regulate Cd accumulation in T. hispida. Twenty-five transcription factors were identified as upstream regulators of hormone-related pathways. ThDRE1A, which was previously identified as an important regulatory factor, was selected for further analysis. The results indicated that ThABAH2.5 and ThACCO3.1 were direct target genes of ThDRE1A. The determination of Cd2+, ABA, and ETH levels indicated that ThDRE1A plays an important role in Cd accumulation through the antagonistic regulation of ABA and ethylene. In conclusion, these results reveal the molecular mechanism underlying Cd accumulation in plants and identify candidate genes for further research."
Authors: Zengkang Zhai, Qianqian Ao, Liuqing Yang, Fangxiao Lu, Haokun Cheng, Qinxin Fang, Chun Li, Qinqin Chen, Jingli Yan, Yongsheng Wei, Yuan-Qing Jiang and Bo Yang.
Journal of Food and Agricultural Chemistry (2024)
Abstract: "Global water deficit is a severe abiotic stress threatening the yielding and quality of crops. Abscisic acid (ABA) is a phytohormone that mediates drought tolerance. Protein kinases and phosphatases function as molecular switches in eukaryotes. Protein phosphatases type 2C (PP2Cs) are a major family that play essential roles in ABA signaling and stress responses. However, the role and underlying mechanism of PP2C in rapeseed (Brassica napus L.) mediating drought response has not been reported yet. Here, we characterized a PP2C family member, BnaPP2C37, and its expression level was highly induced by ABA and dehydration treatments. It negatively regulates drought tolerance in rapeseed. We further identified that BnaPP2C37 interacted with multiple PYR/PYL receptors and a drought regulator BnaCPK5 (calcium-dependent protein kinase 5) through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Specifically, BnaPYL1 and BnaPYL9 repress BnaPP2C37 phosphatase activity. Moreover, the pull-down assay and phosphatase assays show BnaPP2C37 interacts with BnaCPK5 to dephosphorylate BnaCPK5 and its downstream BnaABF3. Furthermore, a dual-luciferase assay revealed BnaPP2C37 transcript level was enhanced by BnaABF3 and BnaABF4, forming a negative feedback regulation to ABA response. In summary, we identified that BnaPP2C37 functions negatively in drought tolerance of rapeseed, and its phosphatase activity is repressed by BnaPYL1/9 whereas its transcriptional level is upregulated by BnaABF3/4."
Authors: Shasha Guo, Junmin Ai, Nannan Zheng, Hairui Hu, Zhuoyi Xu, Quanquan Chen, Li Li, Yunjun Liu, Hongwei Zhang, Jieping Li, Qingchun Pan, Fanjun Chen, Lixing Yuan, Junjie Fu, Riliang Gu, Jianhua Wang and Xuemei Du.
Plant Biotechnology Journal (2024)
Abstract: "Seed vigour, including rapid, uniform germination and robust seedling establishment under various field conditions, is becoming an increasingly essential agronomic trait for achieving high yield in crops. However, little is known about this important seed quality trait. In this study, we performed a genome-wide association study to identify a key transcription factor ZmRap2.7, which regulates seed vigour through transcriptionally repressing expressions of three ABA signalling genes ZmPYL3, ZmPP2C and ZmABI5 and two phosphatidylethanolamine-binding genes ZCN9 and ZCN10. In addition, ZCN9 and ZCN10 proteins could interact with ZmPYL3, ZmPP2C and ZmABI5 proteins, and loss-of-function of ZmRap2.7 and overexpression of ZCN9 and ZCN10 reduced ABA sensitivity and seed vigour, suggesting a complex regulatory network for regulation of ABA signalling mediated seed vigour. Finally, we showed that four SNPs in ZmRap2.7 coding region influenced its transcriptionally binding activity to the downstream gene promoters. Together with previously identified functional variants within and surrounding ZmRap2.7, we concluded that the distinct allelic variations of ZmRap2.7 were obtained independently during maize domestication and improvement, and responded separately for the diversities of seed vigour, flowering time and brace root development. These results provide novel genes, a new regulatory network and an evolutional mechanism for understanding the molecular mechanism of seed vigour."
Authors: Yi-Wen Wang and Savithri U. Nambeesan.
BMC Plant Biology (2024)
Abstract: "Background - Blueberry fruit exhibit atypical climacteric ripening with a non-auto-catalytic increase in ethylene coincident with initiation of ripening. Further, application of ethephon, an ethylene-releasing plant growth regulator, accelerates ripening by increasing the proportion of ripe (blue) fruit as compared to the control treatment. To investigate the mechanistic role of ethylene in regulating blueberry ripening, we performed transcriptome analysis on fruit treated with ethephon, an ethylene-releasing plant growth regulator. Results - RNA-Sequencing was performed on two sets of rabbiteye blueberry (‘Powderblue’) fruit: (1) fruit from divergent developmental stages; and (2) fruit treated with ethephon, an ethylene-releasing compound. Differentially expressed genes (DEGs) from divergent developmental stages clustered into nine groups, among which cluster 1 displayed reduction in expression during ripening initiation and was enriched with photosynthesis related genes, while cluster 7 displayed increased expression during ripening and was enriched with aromatic-amino acid family catabolism genes, suggesting stimulation of anthocyanin biosynthesis. More DEGs were apparent at 1 day after ethephon treatment suggesting its early influence during ripening initiation. Overall, a higher number of genes were downregulated in response to ethylene. Many of these overlapped with cluster 1 genes, indicating that ethylene-mediated downregulation of photosynthesis is an important developmental event during the ripening transition. Analyses of DEGs in response to ethylene also indicated interplay among phytohormones. Ethylene positively regulated abscisic acid (ABA), negatively regulated jasmonates (JAs), and influenced auxin (IAA) metabolism and signaling genes. Phytohormone quantification supported these effects of ethylene, indicating coordination of blueberry fruit ripening by ethylene. Conclusion - This study provides insights into the role of ethylene in blueberry fruit ripening. Ethylene initiates blueberry ripening by downregulating photosynthesis-related genes. Also, ethylene regulates phytohormone-metabolism and signaling related genes, increases ABA, and decreases JA concentrations. Together, these results indicate that interplay among multiple phytohormones regulates the progression of ripening, and that ethylene is an important coordinator of such interactions during blueberry fruit ripening.
Authors: Hikaru Sato and Hisayo Yamane.
Journal of Experimental Botany (2024)
Abstract: "As sessile organisms, plants enter periods of dormancy in response to environmental stresses to ensure continued growth and reproduction in future. During dormancy, plant growth is suppressed, adaptive/survival mechanisms are exerted, and stress tolerance increases over a prolonged period until the plants resume their development or reproduction under favorable conditions. In this review, we focus on seed dormancy and bud dormancy, which are critical for adaptations to fluctuating environmental conditions. We provide an overview of the physiological characteristics of both types of dormancy as well as the importance of the phytohormones abscisic acid and gibberellin for establishing and releasing dormancy, respectively. Additionally, recent epigenetic analyses have revealed that dormancy establishment and release are associated with the removal and deposition of histone modifications at the loci of key regulatory genes influencing phytohormone metabolism and signaling, including DELAY OF GERMINATION 1 and DORMANCY-ASSOCIATED MADS-box genes. We discuss our current understanding of the physiological and molecular mechanisms required to establish and release seed dormancy and bud dormancy, while also describing how environmental conditions control dormancy depth, with a focus on the effects of histone modifications."
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