PIN-LIKES Coordinate Brassinosteroid Signaling with Nuclear Auxin Input in Arabidopsis thaliana

First author: Lin Sun; Affiliations: University of Natural Resources and Life Sciences (自然资源与生命科学大学): Vienna, Austria

Corresponding author: Jürgen Kleine-Vehn

Auxin and brassinosteroids (BR) are crucial growth regulators and display overlapping functions during plant development. Here, we reveal an alternative phytohormone crosstalk mechanism, revealing that BR signaling controls PIN-LIKES (PILS)-dependent nuclear abundance of auxin. We performed a forward genetic screen for imperial pils (imp) mutants that enhance the overexpression phenotypes of PILS5 putative intracellular auxin transport facilitator. Here, we report that the imp1 mutant is defective in the BR-receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1). Our set of data reveals that BR signaling transcriptionally and post-translationally represses the accumulation of PILS proteins at the endoplasmic reticulum, thereby increasing nuclear abundance and signaling of auxin. We demonstrate that this alternative phytohormonal crosstalk mechanism integrates BR signaling into auxin-dependent organ growth rates and likely has widespread importance for plant development.

生长素（auxin）与油菜素内酯（brassinosteroid, BR）都是植物生长的关键调控因子，并且在植物的发育中存在功能重叠。本文中，作者揭示了一种可替换的植物激素交联机制，其中BR信号控制类PIN蛋白PILS依赖型的生长素核富集。作者通过正向遗传学筛选获得了一个imp突变体能够增强PILS5的过表达表型，而PILS5则是一个可能的细胞间生长素转运促进因子。作者发现imp1突变体在BR受体BRI1基因位点上存在缺陷。作者的数据集显示BR信号能够同时在转录水平和翻译后水平抑制PILS蛋白在内质网上的积累，从而增加细胞核中的生长素富集和信号转导。本文的研究揭示了一个植物中的可替代植物激素交联机制，通过将BR信号整合进生长素依赖型的器官生长速率中，该机制很有可能广泛作用于植物的生长发育进程。

（p.s. PILS5OE株系在黑暗条件下相比于野生型下胚轴变短，且部分出现向地性缺陷表型，作者通过对PILS5OE株系进行EMS诱变，结果获得了一个imp1突变体，该突变体不仅在黑暗条件下增强了PILS5OE株系的短下胚轴表型，同时在光照条件下，明显减少了根的伸长。进一步的精细定位和NGS测序分析显示imp1突变是一个BR受体基因BRI1上644号位的甘氨酸（GGT）突变为了丝氨酸（GAT）。）

Highlights

• Impaired BR perception enhances PILS5 overexpression phenotypes

• BR感知缺陷能够增强PILS5过表达的表型

• BR signaling increases PILS protein turnover

• BR信号增加PILS蛋白周转

• BR signaling defines PILS-dependent nuclear abundance and signaling of auxin

• BR信号作用于PILS依赖型的核生长素富集与信号

• PILS-dependent BR-auxin crosstalk affects organ growth

• PILS依赖型的BR-生长素交联能够影响植物器官的生长

通讯：Jürgen Kleine-Vehn (https://boku.ac.at/personen/person/0C9D8AC9D487C1BC)

研究方向：植物生长素依赖性的生长调控。

doi: https://doi.org/10.1016/j.cub.2020.02.002

Journal: Current Biology

Published date: March 12, 2020