Results reveal a signaling module in which GA signaling modulates the degradation of SlGAI, attenuates ethylene (ETH) signaling to inhibit SlXTH19 expression, and regulates stem growth in tomato plants.
Abstract
Stem growth and development greatly influence on plant architecture and yield, which are intimately associated with cell wall remodeling. However, the regulatory mechanisms governing cell-wall remodeling in crops remain poorly understood. Xyloglucan endotransglucosylase/hydrolase (XTH) plays a pivotal role in xyloglucan metabolism. Here, we demonstrated that SlXTH19 controls cell wall remodeling and stem growth. Knockout or knockdown of SlXTH19 decreased cell wall thickness and cellulose and hemicellulose content in tomato stems. We demonstrated that ETHYLENE RESPONSE FACTOR (ERF) transcription factor SlERF1B binds directly to the SlXTH19 promoter, repressing its expression. Knockdown of SlERF1B showed greater stem growth and cell wall composition, whereas SlERF1B-overexpressing plants had a shorter plant heights and thinner stems than the wild type. Further investigation revealed that SlERF1B directly binds to the SlGA3ox1 promoter and represses production of GA. In addition, SlGAI, the core negative regulator of GA signaling, interacts with SlERF1B, and these interactions enhanced the inhibitory effect of SlERF1B on its downstream targets SlXTH19 and SlGA3ox1. Collectively, these results reveal a signaling module in which GA signaling modulates the degradation of SlGAI, attenuates ethylene (ETH) signaling to inhibit SlXTH19 expression, and regulates stem growth in tomato plants.
Brassinazole-resistant1 (BZR1) and BRI1-EMS-suppressor1 (BES1) are phylogenetically closely related transcription factors that act as key components of brassinosteroid (BR) signaling. Although their individual roles in various plant developmental processes have been extensively reported in model plants such as Arabidopsis, their potential synergistic functions in regulating internode length and fruit shape in tomato, an important crop as well as a model system of fruit development, remain unclear. Here, we demonstrate that SlBZR1 and SlBES1 physically interact and modulate internode length and fruit shape in tomato through distinct mechanisms. Genetic analyses reveal that knockout of SlBZR1 or SlBES1 moderately reduces internode length, whereas the bzr1 bes1 double mutant exhibits severe dwarfism. SlBZR1 and SlBES1 promote internode elongation by directly targeting and repressing the expression of GA metabolic gene SlGA2ox10 while inducing that of gibberellin (GA) receptor gene SlGID1A. During fruit development, elongated fruit resulting from enhanced cell proliferation in the ovary wall was observed specifically in the bzr1 bes1 double mutant, but not in bzr1, bes1, BZR1-OE, BES1-OE, and wild-type plants, in a GA-independent manner. We identify the fruit shape regulator SlFS8.1 as a direct transcriptional target of SlBZR1 and SlBES1. Our work demonstrates that SlBZR1 and SlBES1 synergistically promote internode elongation via crosstalk with the GA pathway, while independently governing fruit shape through direct transcriptional activation of SlFS8.1.
Xylem development involves a series of coordinated processes, including cell differentiation, expansion, secondary cell wall (SCW) deposition, and programmed cell death (PCD). Here, we characterize a subtilisin-like serine protease gene, SBT4.1, which exhibits specific expression in stem xylem. Loss of SBT4.1 function results in reduced xylem cell number, smaller cell size, thinner secondary walls, and delayed organelle degradation during PCD. In contrast, SBT4.1 overexpression accelerates cellular clearance and increases xylem cell number, size, and wall thickness, indicating its critical roles in differentiation, SCW synthesis, and PCD. Consistent with a positive regulatory function, pectinase activity and the expression of pectin-related genes are decreased in the mutant but increased in overexpressors. Accordingly, SBT4.1 promotes cell expansion, at least partly, by modulating pectinase activity, as evidenced by enhanced pectin methylesterase (PME) activity upon co-expression with specific PME genes in Nicotiana benthamiana. Molecular analyses revealed that SBT4.1 is a direct transcriptional target of the key SCW regulators SND1, VND6, and MYB46. Furthermore, the expression of SCW synthesis-related genes and PCD-associated protease genes is downregulated in the mutant and upregulated in overexpressing plants. Taken together, our findings demonstrate that SBT4.1, transcriptionally activated by SND1/VND6/MYB46, coordinates xylem cell differentiation, SCW deposition, and PCD, while also promoting cell expansion through modulation of pectin metabolism.
Chong Zhang, Yaoming Xu, Ziyu Ge et al.· Plant physiology and biochem...· 0 citations
Potato growth and development are inhibited by drought stress, which in extreme situations jeopardises tuber yield and quality. Despite progress in understanding drought stress responses, the full regulatory network remains unclear. In this study, we found that the cell wall-localised expansin gene StEXLB1 was significantly induced by polyethylene glycol 6000 (PEG6000) and abscisic acid (ABA). StEXLB1-Overexpression (OE) reduced stomatal density and aperture, accompanied by enhancing drought tolerance. Conversely RNA interference (RNAi) lines exhibited the opposite effects. Further investigation revealed that the transcription factor StMYB55 directly promotes StEXLB1 transcription. Notably, StMYB55-OE resulted in stomatal phenotypes similar to those in StEXLB1-OE lines. Conversely, StMYB55-RNAi increased stomatal density and aperture, as well as reduced drought tolerance. StMYB55 interacts with the ABA receptor StPYL8 and the molecular chaperone StDnaJ3, respectively. This complex then acts to differentially suppress the transcript levels of key stomatal development factors (StSPCH and StFAMA). Genetic evidence showed that StPYL8-RNAi resulted in increased stomatal density and aperture, which was associated with decreased drought tolerance in potato. Collectively, this study suggests that the StMYB55/StPYL8-StEXLB1 module may participate in drought stress response, potentially via stomatal regulation, and provides candidate genes for breeding drought-tolerant potato varieties.
Unknown authors· Plant, Cell and Environment· 0 citations
A positive feedback loop between CLV3 and WUS that is mediated by multiple hormone interactions, which is critical for plants to adapt to harsh environments is revealed.
Mengchu Xu, Haijun Wu, Chengwu Liu et al.· Molecular Plant· 0 citations
Hydrogen sulfide (H2S), a gaseous signaling molecule, retards plant senescence and fruit ripening via protein persulfidation. However, the molecular mechanism underlying its coordination of fruit ripening with plant growth and development remains undefined. This study found that H2S could delay tomato fruit ripening and leaf senescence, and H2S defective mutant sllcd1 shows premature fruit ripening and stunted growth. Overexpression of SlWRKY6, which could be persulfidated by H2S, promotes fruit ripening and reduces fruit number. Molecular assays demonstrated that SlWRKY6 directly binds to the promoter of SlGIF2, a transcriptional co-activator, to repress its expression. Notably, H2S attenuates the repressive effect through persulfidation of SlWRKY6 to increase SlGIF2 transcription. Furthermore, SlGIF2 physically interacts with the GROWTH-REGULATING FACTOR 1 (SlGRF1). Functional validation showed that SlGRF1-SlGIF2 complex serves as a positive regulator of tomato plant growth and fruit yield while concomitantly delaying fruit ripening. Conversely, slgrf1 gene-edited mutants exhibit reduced plant growth, fruit yield and accelerated ripening. Mechanistically, SlGRF1-SlGIF2 complex synergistically activates two downstream target genes: SlCYCD3;1, a key cell-cycle regulator required for cell proliferation and plant growth, and SlCBSX5, which encodes an H2S biosynthesis enzyme that retards fruit ripening. This study provides a module that SlWRKY6-SlGRF1-SlGIF2 integrates H2S signal and genetically coordinates plant growth, fruit yield and fruit ripening in tomato.
Min Zhang, Lisheng Guan, Hongye Sun et al.· Plant Physiology· 0 citations
Tomato (Solanum lycopersicum) β-mannanase is known as playing an important role in mannan degradation; however, its biological functions and transcriptional regulation remain poorly understood. Here, we characterized the roles of mannan-1,4-β-mannanase 2 (SlMAN2) in tomato development and salt stress tolerance. Results showed that SlMAN2 was preferentially expressed in seeds, stems, stamens, and stigmas. SlMAN2 overexpression significantly increased fruit and seed size, accelerated seed germination, and enhanced salt tolerance under 100 mM NaCl, whereas knockout mutants exhibited the opposite phenotypes. Notably, dual-luciferase assays and electrophoretic mobility shift assay (EMSA) demonstrated that the transcription factor SlDOF3.1 directly binds to the SlMAN2 promoter and activates its transcription, but SlMAN2 overexpression suppressed SlDOF3.1 expression, suggesting the existence of a negative feedback regulatory loop. Collectively, our findings reveal that SlMAN2 functions as a pleiotropic regulator coordinating tomato fruit and seed development with salt stress tolerance and uncover a SlDOF3.1–SlMAN2 regulatory module underlying these processes.
Fei-Fei Li, Yang Liu, Shi-Gui Hou et al.· Journal of Agricultural and...· 0 citations
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