The Arabidopsis Nodulin Homeobox Factor AtNDX Interacts with AtRING1A/B and Negatively Regulates Abscisic Acid Signaling

First author: Yujuan Zhu; Affiliations: China Agricultural University (中国农业大学): Beijing, China

Corresponding author: Zhizhong Gong

The phytohormone abscisic acid (ABA) and the Polycomb group (PcG) proteins have key roles in regulating plant growth and development; however, their interplay and underlying mechanisms are not fully understood. Here, we identified an Arabidopsis thaliana nodulin homeobox (AtNDX) protein as a negative regulator in the ABA signaling pathway. AtNDX mutants are hypersensitive to ABA, as measured by inhibition of seed germination and root growth, and the expression of AtNDX is downregulated by ABA. AtNDX interacts with the Polycomb Repressive Complex 1 (PRC1) core components AtRING1A and AtRING1B in vitro and in vivo, and together, they negatively regulate the expression levels of some ABA-responsive genes. We identified ABA-INSENSITIVE (ABI4) as a direct target of AtNDX. AtNDX directly binds the downstream region of ABI4 and deleting this region increases the ABA sensitivity of primary root growth. Furthermore, ABI4 mutations rescue the ABA-hypersensitive phenotypes of ndx mutants and ABI4-overexpressing plants were hypersensitive to ABA in primary root growth. Thus, our work reveals the critical functions of AtNDX and PRC1 in ABA signaling and their regulation of ABI4.

脱落酸ABA和多梳蛋白家族PcG蛋白在调控植物的生长和发育方面发挥非常重要的作用，然而这两者之间的互作以及潜在的分子遗传机制还不清楚。本文中，作者发现拟南芥同源异型蛋白转录因子NDX在ABA信号通路中作为负调控因子发挥功能。AtNDX突变体对于ABA存在超敏感，导致种子萌发和根生长的抑制，并且ABA能够抑制AtNDX基因的表达。无论是体内还是体外试验，AtNDX能够与多梳抑制复合物PRC1核心组成AtRING1A和AtRING1B互作，一起负调控一些ABA响应基因的表达水平。作者发现ABI4基因是AtNDX的直接靶基因。AtNDX能够直接结合到ABI4基因的下游区域，该区域若是被删除会增强主根生长过程中对于ABA的敏感性。此外，ABI4突变体能够拯救ndx突变体对于ABA超敏感的表型，而ABI4过表达植株的主根生长对于ABA表现出超敏反应。因此，本文的研究揭示了AtNDX和PRC1在ABA信号转导以及ABI4转录调控方面的重要作用。

通讯：巩志忠（http://cbs.cau.edu.cn/art/2018/9/14/art_31826_585887.html）

个人简介：1983-1987年，山东师范大学，学士；1987-1990年，中国科学院植物研究所，硕士；1995-1998年，日本千叶大学，博士。

研究方向：植物抗逆。

doi: https://doi.org/10.1105/tpc.19.00604

Journal: Plant Cell

First Published: January 09, 2020