LEAFY activity is post-transcriptionally regulated by BLADE ON PETIOLE2 and CULLIN3 in Arabidopsis

First author: Hicham Chahtane; Affiliations: Université Grenoble Alpes (格勒诺布尔大学): Grenoble, France

Corresponding author: Gilles Vachon

The Arabidopsis LEAFY (LFY) transcription factor is a key regulator of floral meristem emergence and identity. LFY interacts genetically and physically with UNUSUAL FLORAL ORGANS, a substrate adaptor of CULLIN1–RING ubiquitin ligase complexes (CRL1). The functionally redundant genes BLADE ON PETIOLE1 (BOP1) and ‐2 (BOP2) are potential candidates to regulate LFY activity and have recently been shown to be substrate adaptors of CULLIN3 (CUL3)–RING ubiquitin ligases (CRL3). We tested the hypothesis that LFY activity is controlled by BOPs and CUL3s in plants and that LFY is a substrate for ubiquitination (泛素化) by BOP‐containing CRL3 complexes. When constitutively expressed, LFY activity is fully dependent on BOP2 as well as on CUL3A and B to regulate target genes such as APETALA1 and to induce ectopic flower formation. We also show that LFY and BOP2 proteins interact physically and that LFY‐dependent ubiquitinated species are produced in vitro in a reconstituted cell‐free CRL3 system in the presence of LFY, BOP2 and CUL3. This new post‐ ranslational regulation of LFY activity by CRL3 complexes makes it a unique transcription factor subjected to a positive dual regulation by both CRL1 and CRL3 complexes and suggests a novel mechanism for promoting flower development.

拟南芥LEAFY转录因子是花分生组织发生和决定的重要调控子。LFY能够与CULLIN1–RING泛素连接酶复合物CRL1的底物接头UNUSUAL FLORAL ORGANS相互作用。功能上存在冗余的BOP1和BOP2基因是调控LFY活性的潜在候选基因，最近有研究指出这两个蛋白可能是CULLIN1–RING泛素连接酶复合物CRL3的底物接头。本文的研究验证了植物中的BOPs和CUL3s是否调控LFY活性，并且LFY是否是包含BOP的CRL3复合物的泛素化底物。当组成型表达时，LFY活性完全依赖于BOP2基因，以及CUL3A和CUL3B，一起调控其靶基因，如APETALA1基因，进而诱导花的异位形成。进一步的研究显示LFY和BOP2蛋白物理上能够相互作用，并且离体重构的非细胞CRL3系统中在存在LFY、BOP2和CUL3的情况下能够产生LFY依赖型泛素化物质。本文揭示的CRL3复合物对于LFY活性的转录后调控结合已有的研究结果说明了CRL1和CRL3复合物正向双重调控LFY活性的独特机制，进而促进花发育。

doi: https://doi.org/10.1111/nph.15329

Journal: New Phytologist

First Published: 11 July, 2018

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