A phosphorylation-based switch controls TAA1-mediated auxin biosynthesis in plants

First author: Qian Wang; Affiliations: CAS Centre for Excellence in Molecular Plant Sciences (中科院分子植物科学卓越创新中心): Shanghai, China

Corresponding author: Tongda Xu

Auxin determines the developmental fate of plant tissues, and local auxin concentration is precisely controlled. The role of auxin transport in modulating local auxin concentration has been widely studied but the regulation of local auxin biosynthesis is less well understood. Here, we show that TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA1), a key enzyme in the auxin biosynthesis pathway in Arabidopsis thaliana is phosphorylated at Threonine 101 (T101). T101 phosphorylation status can act as an on/off switch to control TAA1-dependent auxin biosynthesis and is required for proper regulation of root meristem size and root hair development. This phosphosite is evolutionarily conserved suggesting post-translational regulation of auxin biosynthesis may be a general phenomenon. In addition, we show that auxin itself, in part via TRANS-MEMBRANE KINASE 4 (TMK4), can induce T101 phosphorylation of TAA1 suggesting a self-regulatory loop whereby local auxin signalling can suppress biosynthesis. We conclude that phosphorylation-dependent control of TAA1 enzymatic activity may contribute to regulation of auxin concentration in response to endogenous and/or external cues.

生长素决定着植物组织的发育命运，局部的生长素浓度受到严格的调控。生长素转运在调节局部生长素浓度中的作用已经被广泛研究，但是目前对于局部的生长素合成调控机制还不是很清楚。本文中，作者发现拟南芥中一个生长素合成关键酶TAA1的101号氨基酸苏氨酸（T101）被磷酸化，而该位点上的磷酸化状态可以激活或关闭TAA1依赖型的生长素合成，且对于根分生组织大小以及根毛发育的恰当调控是必需的。TAA1上T101位点的磷酸化在演化上十分保守，说明生长素合成的翻译后调控可能是一个比较常见的现象。另外，作者还发现生长素本身会通过TMK4诱导TAA1上T101位点的磷酸化，说明存在一个自调控的环，从而局部的生长素信号可以抑制生长素的合成。作者得出的结论是植物响应于内部或外部的信号，通过磷酸化依赖性的TAA1酶活调控作用于生长素浓度的调控。

通讯：徐通达 (http://net.fafu.edu.cn/hist/6a/fd/c6023a223997/page.htm)

个人简介：1999-2003年，北京大学，学士；2005-2010年，美国加州大学河边分校，博士。

研究方向：生长素对细胞分裂模式的调节机制；生长素细胞膜与细胞核内信号途径偶联调节的分子机制；植物生长素调节调节的农业应用。

doi: https://doi.org/10.1038/s41467-020-14395-w

Journal: Nature Communications

Published date: February 03, 2020