AtVQ25 promotes salicylic acid-related leaf senescence by fine-tuning the self-repression of AtWRKY53

Most mechanistic details of chronologically ordered regulation of leaf senescence are unknown.Regulatory networks centered on AtWRKY53 are crucial for orchestrating and integrating various senescence-related signals.Notably,AtWRKY53binds to its own promoter and represses transcription of AtWRKY53,but the biological significance and mechanism underlying this selfrepression remain unclear.In this study,we identified the VQ motif-containing protein AtVQ25as a cooperator of AtWRKY53.The expression level of AtVQ25 peaked at mature stage and was specifically repressed after the onset of leaf senescence.AtVQ25-overexpressing plants and atvq25 mutants displayed precocious and delayed leaf senescence,respectively.Importantly,we identified AtWRKY53 as an interacting partner of AtVQ25.We determined that interaction between AtVQ25 and AtWRKY53 prevented AtWRKY53from binding to W-box elements on the AtWRKY53promoter and thus counteracted the selfrepression of AtWRKY53.In addition,our RNA-sequencing data revealed that the AtVQ25-AtWRKY53 module is related to the salicylic acid(SA)pathway.Precocious leaf senescence and SA-induced leaf senescence in AtVQ25-overexpressing lines were inhibited by an SA pathway mutant,atsid2,and Nah G transgenic plants;AtVQ25-overexpressing/atwrky53 plants were also insensitive to SA-induced leaf senescence.Collectively,we demonstrated that AtVQ25 directly attenuates the self-repression of AtWRKY53 during the onset of leaf senescence,which is substantially helpful for understanding the timing of leaf senescence onset modulated by AtWRKY53.

The SlWRKY57-SlVQ21/SlVQ16 module regulates salt stress in tomato

Salt stress is a major abiotic stress which severely hinders crop production.However,the regulatory network controlling tomato resistance to salt remains unclear.Here,we found that the tomato WRKY transcription factor WRKY57 acted as a negative regulator in salt stress response by directly attenuating the transcription of salt-responsive genes(Sl RD29B and Sl DREB2)and an ion homeostasis gene(Sl SOS1).We further identified two VQ-motif containing proteins Sl VQ16 and Sl VQ21as Sl WRKY57-interacting proteins.Sl VQ16 positively,while Sl VQ21 negatively modulated tomato resistance to salt stress.Sl VQ16 and Sl VQ21 competitively interacted with Sl WRKY57 and antagonistically regulated the transcriptional repression activity of Sl WRKY57.Additionally,the Sl WRKY57-Sl VQ21/Sl VQ16 module was involved in the pathway of phytohormone jasmonates(JAs)by interacting with JA repressors JA-ZIM domain(JAZ)proteins.These results provide new insights into how the Sl WRKY57-Sl VQ21/Sl VQ16 module finely tunes tomato salt tolerance.

Protein-Protein Interactions in the Regulation of WRKY Transcription Factors

It has been almost 20 years since the first report of a WRKY transcription factor, SPF1, from sweet potato. Great progress has been made since then in establishing the diverse biological roles of WRKY transcription factors in plant growth, development, and responses to biotic and abiotic stress. Despite the functional diversity, almost all ana-lyzed WRKY proteins recognize the TrGACC/T W-box sequences and, therefore, mechanisms other than mere recognition of the core W-box promoter elements are necessary to achieve the regulatory specificity of WRKY transcription factors. Research over the past several years has revealed that WRKY transcription factors physically interact with a wide range of proteins with roles in signaling, transcription, and chromatin remodeling. Studies of WRKY-interacting proteins have provided important insights into the regulation and mode of action of members of the important family of transcrip-tion factors. It has also emerged that the slightly varied WRKY domains and other protein motifs conserved within each of the seven WRKY subfamilies participate in protein-protein interactions and mediate complex functional interactions between WRKY proteins and between WRKY and other regulatory proteins in the modulation of important biologi- cal processes. In this review, we summarize studies of protein-protein interactions for WRKY transcription factors and discuss how the interacting partners contribute, at different levels, to the establishment of the complex regulatory and functional network of WRKY transcription factors.