Circadian control of abscisic acid biosynthesis and signalling pathways revealed by genome-wide analysis of LHY binding targets

First author: Sally Adams; Affiliations: University of Warwick (华威大学): Coventry, UK

Corresponding author: Isabelle A. Carré

The LATE ELONGATED HYPOCOTYL (LHY) transcription factor functions as part of the oscillatory mechanism of the Arabidopsis circadian clock. This paper reports the genome-wide analysis of its binding targets and reveals a role in the control of abscisic acid (ABA) biosynthesis and downstream responses. LHY directly repressed expression of 9-cis-epoxycarotenoid dioxygenase enzymes (9-顺式环氧类胡萝卜素双加氧酶), which catalyse the rate-limiting step of ABA biosynthesis. This suggested a mechanism for the circadian control of ABA accumulation in wild-type plants. Consistent with this hypothesis, ABA accumulated rhythmically in wild-type plants, peaking in the evening. LHY-overexpressing plants had reduced levels of ABA under drought stress, whereas loss-of-function mutants exhibited an altered rhythm of ABA accumulation. LHY also bound the promoter of multiple components of ABA signalling pathways, suggesting that it may also act to regulate responses downstream of the hormone. LHY promoted expression of ABA-responsive genes responsible for increased tolerance to drought and osmotic stress (渗透胁迫) but alleviated (减轻) the inhibitory effect of ABA on seed germination and plant growth. This study reveals a complex interaction between the circadian clock and ABA pathways, which is likely to make an important contribution to plant performance under drought and osmotic stress conditions.

LHY转录因子在拟南芥的生物钟中发挥重要作用。本文报道了LHY在基因组范围的靶向位点，揭示了其在脱落酸ABA生物合成及下游信号转导等方面的调控作用。LHY能够直接抑制ABA生物合成限速酶9-顺式环氧类胡萝卜素双加氧酶的表达水平，说明了LHY在野生型拟南芥中对ABA的积累有昼夜节律的调控。不出所料，在野生型拟南芥中，ABA的积累确实存在节律性，在晚上达到最高峰。LHY过表达植株在干旱胁迫下ABA水平降低，而LHY功能缺失突变体ABA积累的节律性发生改变。LHY同样能够结合到多个ABA信号通路基因的启动子，说明LHY可能能够调控ABA信号转导下游的响应过程。LHY促进了ABA响应基因的表达，进而作用于提升植株对于干旱和渗透胁迫的抗性，但也减少了种子萌发和植株生长期间的ABA抑制效应。本文的研究揭示了生物钟与ABA之间的复杂调控关系，可能对于植物在干旱和渗透胁迫下的表现提供了新的见解。

通讯：Isabelle A. Carré（https://warwick.ac.uk/fac/sci/lifesci/people/icarre/）

个人简介：1992年，纽约州立石溪大学，博士。

研究方向：植物生物钟和光周期开花潜在的基因调控网络；基因启动子区与基因特异性时空表达相关的调控位点。

doi: https://doi.org/10.1111/nph.15415

Journal: New Phytologist

First Published: 07 September, 2018

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