Arabidopsis ZINC FINGER PROTEIN1 Acts Downstream of GL2 To Repress Root Hair Initiation and Elongation by Directly Suppressing bHLH Genes

First author: Guo-Liang Han; Affiliations: Shandong Normal University (山东师范大学): Jinan, China

Corresponding author: Baoshan Wang

C2H2-type zinc finger proteins play positive roles in root hair growth and development by regulating their target genes. However, little is known about their potential negative roles in root hair initiation and elongation. Here we show that the C2H2-type zinc finger protein AtZP1, which contains an EAR motif, negatively regulates Arabidopsis thaliana root hair initiation and elongation. Our results demonstrate that AtZP1 is highly expressed in root hairs and that AtZP1 inhibits transcriptional activity during root hair development. Plants overexpressing AtZP1 lacked root hairs, while loss-of-function mutants had longer and more numerous root hairs than wild type. Transcriptome analysis indicated that AtZP1 downregulates genes encoding bHLH transcription factors associated with root hair cell differentiation and elongation. Mutation or deletion of the EAR motif significantly reduced the inhibitory activity of AtZP1. Chromatin immunoprecipitation (ChIP) assays, AtZP1:GR induction experiments, electrophoretic mobility shift assays (EMSAs), and yeast one-hybrid assays showed that AtZP1 directly targets the promoters of bHLH transcription factor genes, including the key root hair initiation gene ROOT HAIR DEFECTIVE6 (RHD6) and root hair elongation genes ROOT HAIR DEFECTIVE 6-LIKE 2 (RSL2) and RSL4, to suppress root hair development. Our findings suggest that AtZP1 functions downstream of GL2 to negatively regulate root hair initiation and elongation, by suppressing RHD6, RSL4, and RSL2 transcription via the GL2/ZP1/RSL pathway.

植物C2H2类的锌指蛋白在根毛生长和发育过程中通过调控其靶基因发挥着正向的调控作用。然而，有关这类蛋白在根毛抑制和伸长方面的负调控作用还不清楚。本文中，作者的研究揭示了一个含有EAR基序的C2H2类锌指蛋白AtZP1负调控拟南芥根毛的抑制和伸长。作者发现AtZP1基因在根毛中高表达，并且AtZP1会在根毛发育过程中抑制转录活性。过表达AtZP1的植株会缺失根毛，而AtZP1基因的功能缺失突变体则比野生型有更长、更多的根毛。转录组分析显示AtZP1会下调与根毛细胞分化和伸长相关的bHLH转录因子。突变或删除AtZP1蛋白中的EAR基序会显著降低其抑制活性。染色质免疫沉淀试验ChIP、AtZP1:GR诱导试验、电泳迁移率变动分析EMSA以及酵母单杂试验均显示AtZP1蛋白能够直接靶向bHLH转录因子的启动子，包括关键的根毛抑制基因RHD6和根毛伸长基因RSL2/4，从而抑制根毛的发育。本文的研究揭示了AtZP1基因作为GL2的下游，通过抑制RHD6和基因RSL2/4，组成了一个GL2/ZP1/RSL通路，负调控根毛的抑制和伸长。

通讯：王宝山 (http://www.lsc.sdnu.edu.cn/info/1086/1950.htm)

个人简介：1985年，西北师范大学，硕士；1996年，山东农业大学，博士。

研究方向：主要从事植物耐盐生理及分子机理、耐盐经济植物育种及配套栽培技术研究。

doi: https://doi.org/10.1105/tpc.19.00226

Journal: Plant Cell

First Published: November 15, 2019