Light‐induced stabilization of ACS contributes to hypocotyl elongation during the dark‐to‐light transition in Arabidopsis seedlings

First author: Dong Hye Seo; Affiliations: Purdue University (普渡大学): West Lafayette, USA

Corresponding author: Gyeong Mee Yoon

Hypocotyl growth during seedling emergence is a crucial developmental transition influenced by light and phytohormones such as ethylene. Ethylene and light antagonistically control hypocotyl growth in either continuous light or darkness. However, how ethylene and light regulate hypocotyl growth, including seedling emergence, during the dark‐to‐light transition remains elusive. Here, we show that ethylene and light cooperatively stimulate a transient increase in hypocotyl growth during the dark‐to‐light transition via the light‐mediated stabilization of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) synthases (ACSs), the rate‐limiting enzymes in ethylene biosynthesis. We found that, in contrast to the known inhibitory role of light in hypocotyl growth, light treatment transiently increases hypocotyl growth in wild‐type etiolated seedlings. Moreover, ACC, the direct precursor of ethylene, accentuates the effects of light on hypocotyl elongation during the dark‐to‐light transition. We determined that light leads to the transient elongation of hypocotyls by stabilizing the ACS5 protein during the dark‐to‐light transition. Furthermore, biochemical analysis of an ACS5 mutant protein bearing an alteration in the C‐terminus indicated that light stabilizes ACS5 by inhibiting the degradation mechanism that acts through the C‐terminus of ACS5. Our study reveals that plants regulate hypocotyl elongation during seedling establishment by coordinating light‐induced ethylene biosynthesis at the post‐translational level. Moreover, the stimulatory role of light on hypocotyl growth during the dark‐to‐light transition provides additional insights into the known inhibitory role of light in hypocotyl development.

植物出苗时期下胚轴的生长是一个重要的发育转变，该过程受到光照以及乙烯等植物激素的影响。无论是在连续光照或是黑暗条件下，乙烯和光照拮抗控制下胚轴的生长。然而，目前我们还不清楚乙烯和光照是如何调控下胚轴生长的，包括在植物从黑暗到光照的状态转变过程中的出苗。本文的研究显示乙烯和光照通过由光介导的1-氨基环丙烷-1-羧酸合酶ACS的稳定协同刺激下胚轴的瞬间生长，而ACS是乙烯生物合成中的一个限速酶。作者发现，与已知的光照抑制下胚轴生长相反，光照处理能够瞬间增加野生型黄化苗下胚轴的生长。此外，乙烯的直接前体ACC加强了光照对于下胚轴的影响。另外，对于ACS5蛋白C端突变的生化分析显示，光照通过抑制作用于ACS5的C端的降解机制来稳定ACS5蛋白。本文的研究揭示了植物通过转录后水平协调光诱导的乙烯生物合成，从而调控幼苗建立时期的下胚轴伸长。此外，本文的研究显示的光照对于植物黑暗到光照状态转变时期的下胚轴伸长具有促进作用，这一结果与之前光照对于下胚轴的抑制作用结论相反，为光照在植物下胚轴生长中的作用提供了一个新的视野。

通讯：Gyeong Mee Yoon (https://ag.purdue.edu/btny/Pages/Profile.aspx?strAlias=yoong&intDirDeptID=10)

研究方向：植物激素乙烯的生物和成与信号转导。

doi: https://doi.org/10.1111/tpj.14289

Journal: the plant journal

Published online: March 27, 2019