The photomorphogenic repressors BBX28 and BBX29 integrate light and brassinosteroid signaling to inhibit seedling development in Arabidopsis

第一作者：Jing Cao

第一单位：兰州大学

通讯作者：Fang Lin

 Abstarct 

背景回顾：B-box containing proteins (BBXs) integrate light and various hormonal signals to regulate plant growth and development. 

BBXs蛋白整合光和多种激素信号以调控植物的生长和发育。

主要研究：Here, we demonstrate that the photomorphogenic repressors BBX28 and BBX29 positively regulate brassinosteroid (BR) signaling in Arabidopsis thaliana seedlings. 

本文中，作者发现拟南芥幼苗中光形态发生抑制因子BBX28和BBX29正调控油菜素内酯（BR）信号转导。

结果1-BR-BBX28/29：Treatment with the BR brassinolide stabilized BBX28 and BBX29, which partially depended on BR INSENSITIVE1 (BRI1) and BR-INSENSITIVE2 (BIN2). 

通过油菜素内酯的处理能够稳定BBX28和BBX29，这部分依赖于BRI1和BIN2。

结果2-BBX28/29敲除和过表达：bbx28 bbx29 seedlings exhibited larger cotyledon aperture than the wild type when treated with brassinazole in the dark, which partially suppressed the closed cotyledons of brassinazole resistant 1-1D (bzr1-1D). Consistently, overexpressing BBX28 and BBX29 partially rescued the short hypocotyls of bri1-5 and bin2-1 in both the dark and light, while the loss-of-function of BBX28 and BBX29 partially suppressed the long hypocotyls of bzr1-1D in the light. 

黑暗条件下，利用油菜素内酯处理，bbx28 bbx29双突变体的幼苗的子叶孔径相较于野生型更大，并且能够部分抑制bzr1-1D突变体子叶闭合的表型。BBX28和BBX29的过表达能够部分恢复光照和黑暗条件下bri1-5和bin2-1突变体的短下胚轴表型，而BBX28和BBX29的功能缺失则会部分抑制bzr1-1D突变体在光下的长下胚轴表型。

结果3-BBX28/29-BEE1/2/3-BR信号转导：BBX28 and BBX29 physically interacted with BR-ENHANCED EXPRESSION1 (BEE1), BEE2, and BEE3 and enhanced their binding to and activation of their target genes. Moreover, BBX28 and BBX29 as well as BEE1, BEE2, and BEE3 increased BZR1 accumulation to promote the BR signaling pathway. Therefore, both BBX28 and BBX29 interact with BEE1, BEE2, and BEE3 to orchestrate light and BR signaling by facilitating the transcriptional activity of BEE target genes. 

BBX28和BBX29能够与BEE1、BEE2和BEE3物理互作，以增强其结合并激活下游靶基因的能力。此外，BBX28/29和BEE1/2/3能够增加BZR1的积累，从而促进BR信号转导途径。因此，BBX28/29与BEE1/2/3互作，通过促进BEE靶基因的转录调控，从而调控光和BR信号转导。

结论：Our study provides insights into the pivotal roles of BBX28 and BBX29 as signal integrators in ensuring normal seedling development.

本文的研究揭示了BBX28和BBX29作为信号整合因子，在确保幼苗的正常发育方面发挥重要作用。

** 林 芳 **

doi: https://doi.org/10.1093/plcell/koac092

Journal: The Plant Cell​

Published date:  March 16, 2022