[植物生理] 植物生長素調控的另一面。 20191018 EMBO Jounral

Plasmodesmata
Oct 18, 2019
2 min read

Non-canonical AUX/IAA protein IAA33 competes with canonical AUX/IAA repressor IAA5 to negatively regulate auxin signaling

Bingsheng Lv, Qianqian Yu, Jiajia Liu, Xuejing Wen, Zhenwei Yan, Kongqin Hu,

Hanbing Li, Xiangpei Kong, Cuiling Li, Huiyu Tian, Ive De Smet, Xian-Sheng Zhang & Zhaojun Ding

Abstract

The phytohormone auxin controls plant growth and development via TIR1-dependent protein degradation of canonical AUX/IAA proteins, which normally repress the activity of auxin response transcription factors (ARFs). IAA33 is a non-canonical AUX/IAA protein lacking a TIR1-binding domain, and its role in auxin signaling and plant development is not well understood. Here, we show that IAA33 maintains root distal stem cell identity and negatively regulates auxin signaling by interacting with ARF10 and ARF16. IAA33 competes with the canonical AUX/IAA repressor IAA5 for binding to ARF10/16 to protect them from IAA5-mediated inhibition. In contrast to auxin-dependent degradation of canonical AUX/IAA proteins, auxin stabilizes IAA33 protein via MITOGEN-ACTIVATED PROTEIN KINASE 14 (MPK14) and does not affect IAA33 gene expression. Taken together, this study provides insight into the

molecular functions of non-canonical AUX/IAA proteins in auxin signaling transduction.

非典型的AUX/IAA蛋白質，IAA33，利用與典型的AUX/IAA抑制蛋白質IAA5競爭來抑制生長素訊息傳導

摘要

植物荷爾蒙 - 生長素，經由與受體TIR1蛋白結合而引發傳統AUX/IAA蛋白質降解。這解除了AUX/IAA因為與生長素反應因子結合，而進行的抑制基因轉錄，最終控制植物的生長與發育。IAA33是一個非典型的AUX/IAA蛋白質，它缺少了可以與受體蛋白TIR1互動的區域，而它在生長素訊息傳遞和植物生長與發育的角色仍然未知。在此，我們顯示了IAA33維持了根部遠端幹細胞的細胞身份，並且經由與生長素反應因子ARF10、ARF16互動來負向調控生長素訊息。IAA33利用和傳統的IAA5競爭同樣的互動蛋白，來保護ARF10/16免於被IAA5結合而抑制下游基因表現。與傳統的生長素訊息傳遞相反的是，IAA33不會因為生長素而引發降解，反而生長素會經由MAPK14來穩定IAA33，而且這個穩定現象別不會影響IAA33的基因表現亮。總結，這個研究提供了對於非典型的AUX/IAA蛋白在生長素訊息傳遞機制中的分子作用，提供了一個新的可能機制。