Transcription factor WRKY46 modulates the development of Arabidopsis lateral roots in osmotic/salt stress conditions via regulation of ABA signaling and auxin homeostasis. (18th September 2015)

• Record Type: Journal Article
• Authors: Ding, Zhong Jie; Yan, Jing Ying; Li, Chun Xiao; Li, Gui Xin; Wu, Yun Rong; Zheng, Shao Jian
• Is Part Of: Plant journal. Volume 84:Number 1(2015:Oct.)
• Page Start: 56
• Page End: 69
• Publication Date: 2015-09-18
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12958
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12958-abs-0001"> <title>Summary</title> <p>The development of lateral roots (LR) is known to be severely inhibited by salt or osmotic stress. However, the molecular mechanisms underlying LR development in osmotic/salt stress conditions are poorly understood. Here we show that the gene encoding the WRKY transcription factor WRKY46 (<italic>WRKY46</italic>) is expressed throughout lateral root primordia (LRP) during early LR development and that expression is subsequently restricted to the stele of the mature LR. In osmotic/salt stress conditions, lack of WRKY46 (in loss‐of‐function <italic>wrky46</italic> mutants) significantly reduces, while overexpression of WRKY46 enhances, LR development. We also show that exogenous auxin largely restores LR development in <italic>wrky46</italic> mutants, and that the auxin transport inhibitor 2, 3, 5‐triiodobenzoic acid (TIBA) inhibits LR development in both wild‐type (WT; Col‐0) and in a line overexpressing <italic>WRKY46</italic> (OV46). Subsequent analysis of abscisic acid (ABA)‐related mutants indicated that <italic>WRKY46</italic> expression is down‐regulated by ABA signaling, and up‐regulated by an ABA‐independent signal induced by osmotic/salt stress. Next, we show that expression of the <italic>DR5:GUS</italic> auxin response reporter is reduced in roots of <italic>wrky46</italic> mutants, and that both <italic>wrky46</italic> mutants and OV46 display altered root levels of free indole‐3‐acetic acid (IAA) and IAA conjugates. Subsequent RT‐qPCR and ChIP‐qPCR experiments indicated that WRKY46 directly regulates the expression of <italic>ABI4</italic> and of genes regulating auxin conjugation. Finally, analysis of <italic>wrky46 abi4</italic> double mutant plants confirms that ABI4 acts downstream of WRKY46. In summary, our results demonstrate that WRKY46 contributes to the feedforward inhibition of osmotic/salt stress‐dependent LR inhibition via regulation of ABA signaling and auxin homeostasis.</p> </abstract>