WRKY Transcription Factor OsWRKY29 Represses Seed Dormancy in Rice by Weakening Abscisic Acid Response.

Chunlei Zhou,Xi Liu,Xin Zhang,Rong Miao,Xiuping Guo,Changling Mou,Xingjie Zhu,Liang Zhou,Tianyu Zhang,Shijia Liu,Jianmin Wan,Qibing Lin,Xiao Zhang,Jiachang Wang,Thanhliem Nguyen,Qian Wang,Jie Lan,Ling Jiang

doi:10.3389/fpls.2020.00691

Abstract

For efficient plant reproduction, seed dormancy delays seed germination until the environment is suitable for the next generation growth and development. The phytohormone abscisic acid (ABA) plays important role in the induction and maintenance of seed dormancy. Previous studies have identified that WRKY transcription factors can regulate ABA signaling pathway. Here, we identified an Oswrky29 mutant with enhanced dormancy in a screen of T-DNA insertion population. OsWRKY29 is a member of WRKY transcription factor family which located in the nuclear. The genetic analyses showed that both knockout and RNAi lines of OsWRKY29 had enhanced seed dormancy whereas its overexpression lines displayed reduced seed dormancy. When treated with ABA, OsWRKY29 knockout and RNAi lines showed greater sensitivity than its overexpression lines. In addition, the expression levels of ABA positive response factors OsVP1 and OsABF1 were higher in the OsWRKY29 mutants but were lower in its overexpression lines. Further assays showed that OsWRKY29 could bind to the promoters of OsABF1 and OsVP1 to inhibit their expression. In summary, we identified a new ABA signaling repressor OsWRKY29 that represses seed dormancy by directly downregulating the expression of OsABF1 and OsVP1.

Highlights

The core role of seeds is to reproduce offspring
To test if the T-DNA insertion affected the transcription of OsWRKY29, we performed RT-qPCR and found that the expression of OsWRKY29 was reduced in the mutant relative to the wild type Hwayoung (Hy) (Figure 1C)
OsWRKY29 expression is negatively related to seed dormancy during seed development or seed germination (Figure 1F and Supplementary Figures S3, S5F) and its expression was inhibited by abscisic acid (ABA) in germinating seeds and early seedlings (Supplementary Figures S5F, S6)

Summary

INTRODUCTION

The core role of seeds is to reproduce offspring. Seed plants have evolved diverse strategies to ensure survival of their offspring. WRKY transcription factors can bind to the same W-box they still have functional differences in regulating seed dormancy by modulating the ABA signaling pathway. Some WRKY proteins promote seed dormancy by positively modulating ABA-responsive genes. Some WRKY proteins repress seed dormancy by negatively modulating ABA-responsive genes. We identified a new WRKY transcription factor, OsWRKY29, which negatively regulates seed dormancy in rice. The expression of ABA positive response genes OsABF1 and OsVP1 was increased in OsWRKY29 mutants but reduced in OsWRKY29-overexpression lines. Further analyses showed that OsWRKY29 directly binds to W-boxes in the promoters of OsABF1 and OsVP1 to repress their expression These results suggest that OsWRKY29 represses seed dormancy by weakening ABA response

MATERIALS AND METHODS

Evaluation of Seed Dormancy

RESULTS

DISCUSSION

DATA AVAILABILITY STATEMENT