OsWRKY53 Promotes Abscisic Acid Accumulation to Accelerate Leaf Senescence and Inhibit Seed Germination by Downregulating Abscisic Acid Catabolic Genes in Rice

Abstract

Abscisic acid (ABA) largely promotes leaf senescence and inhibits seed germination in plants. Endogenous ABA content is finely tuned by many transcription factors. In this study, we showed that OsWRKY53 is a positive regulator of leaf senescence and a negative regulator of seed germination in rice. OsWRKY53 expression was induced in leaves under aging, dark, and ABA treatment. The OsWRKY53-overexpressing (OsWRKY53-oe) plants showed early yellowing leaves, while the OsWRKY53 (oswrky53) knockout mutants maintained green leaves than the wild type under natural, dark-induced, and ABA-induced senescence conditions. Transcriptional analysis revealed that ABA catabolic genes, namely, OsABA8ox1 and OsABA8ox2, two key genes participating in ABA catabolism harboring ABA 8′-hydroxylase activity, were markedly downregulated in OsWRKY53-oe leaves. Chromatin immunoprecipitation and protoplast transient assays revealed that OsWRKY53 directly bound to the promoters of OsABA8ox1 and OsABA8ox2 to repress their transcription, resulting in elevated endogenous ABA contents that promoted premature leaf senescence in the OsWRKY53-oe plants. It indicates that OsWRKY53 is a positive regulator through regulating ABA accumulation to promote leaf senescence. In addition, accumulated ABA simultaneously inhibited seed germination and post-germination growth in OsWRKY53-oe plants. Taken together, OsWRKY53 suppresses the transcript of ABA catabolic genes to promote ABA accumulation to modulate ABA-induced leaf senescence and ABA-mediated inhibition of seed germination.

Brassica napus Transcription Factor Bna.A07.WRKY70 Negatively Regulates Leaf Senescence in Arabidopsis thaliana

“…The cotton ( Gossypium hirsutum L.) GhWRKY91 directly targets GhWRKY17 , a gene associated with ABA signals and reactive oxygen species (ROS) production to negatively mediate leaf senescence and provide a foundation for further functional studies on natural and stress-induced leaf senescence [ 40 ]. OsWRKY53 of rice, as a positive regulator, repressed the transcript of ABA catabolic genes ( OsABA8ox1 and OsABA8ox2 ) by directly binding to their promoters to promote ABA accumulation, and modulated ABA-induced leaf senescence [ 41 ]. In Arabidopsis , AtWRKY70 transcript levels were more strongly reduced in npr1 ( non-expressor of PR 1 ) and pad4 ( phytoalexin-deficient 4 ) and completely abolished in NahG (salicylate hydroxylase gene) plants compared to wild-type at 40 days post germination, among which, the NahG , pad4 , and npr1 belonged to SA mutants and exhibited a delayed senescence phenotype [ 3 ].…”

GhWRKY33 Interacts with GhTIFY10A to Synergistically Modulate Both Ageing and JA-Mediated Leaf Senescence in Arabidopsis

“…For example, AtWRKY45 interacts with DELLA protein RGL1 to positively regulates GA-mediated leaf senescence, while AtWRKY75 directly promotes SA INDUCTIONDEFICIENT2 ( SID 2) expression to promote SA production and finally accelerates leaf senescence [ 4 , 31 ]. Recently, OsWRKY53 was shown to accelerate leaf senescence through the promotion of ABA accumulation, and AtWRKY75 can also play a role in ABA-mediated leaf senescence [ 21 , 32 ]. Although several cotton WRKY members, including GbWRKY27 , GhWRKY42 , and GhWRKY91 , have been shown to play important roles in leaf senescence [ 15 , 16 , 17 ], it is still unclear whether they can regulate leaf senescence through interaction with certain phytohormones.…”

Understanding of Hormonal Regulation in Rice Seed Germination

“…In rice, OsWRKY72 and OsWRKY77 enhanced transcription from the promoter of the ABA-responsive gene HVA22 under ABA treatment [ 114 ]. OsWRKY53 directly binds to the promoters of OsABA8ox1 and OsABA8ox2 (ABA catabolic genes) to repress their expression, leading to the accumulation of ABA and furthering the inhibition of seed germination [ 115 ]. However, WRKY TFs have functional differences in regulating seed germination, because several WRKY proteins were found to promote seed germination by negatively modulating ABA-responsive genes [ 116 ].…”