拟南芥ABFs转录因子介导ABA调控根可塑性生长的分子机理

Plasticity of root growth is one of the important means for plants to adapt to the various environmental cues. Abscisic acid (ABA) is an important stress hormone in plants, involved in regulation of root growth. It was known that the key components of the ABA signaling pathway are involved in the regulation of root growth, however, the underlying molecular mechanisms are poorly understood. In previous study, we identified ABF4, an important transcription factor in ABA signaling pathway, can directly bind to YUCCA9 (YUC9) promoter, which encodes a key enzyme of auxin biosynthesis. Further results suggested ABF4 activated YUC9 expression. Yucasin, an inhibitor of YUC activity, can alleviates the inhibition of primary root growth caused by ABA in WT plants, and yuc mutants were less sensitive to ABA during primary root growth. These indicate that YUCs are sufficient for root-growth regulation by ABA. This project will detailedly investigate the molecular mechanism of ABFs in regulating YUCs genes by genetics, cell biology, biological chemistry and molecular biology approaches, thus further deepening our understanding of the regulatory networks of ABA signaling involved in plant root growth and the crosstalk between ABA signaling pathway and auxin in plasticity of root growth.

植物根的可塑性生长是其适应环境，应对各种逆境胁迫的重要手段之一。脱落酸（abscisic acid，ABA）作为一种重要的逆境激素参与调节植物根的可塑性生长。已有研究发现ABA信号转导中的几个关键组分都参与调控根的生长发育，但其作用的分子机制尚不明确。本项目前期研究发现ABA信号通路中关键转录因子ABF4可以直接结合生长素合成酶关键基因YUCCA9（YUC9）启动子并正调控其表达。施加YUC抑制剂yucasin能缓解ABA对野生型植株主根生长的抑制，yuc突变体表现出对ABA抑制主根伸长不敏感的表型，说明YUCs参与ABA调控根生长这一生理过程。本项目拟综合运用遗传学、细胞生物学、生物化学和分子生物学等手段详细分析ABFs转录因子调控YUCs基因表达的分子机制，阐述ABA信号参与拟南芥根生长发育的调控网络，以及ABA信号如何与生长素交叉互作调控根的可塑性生长。

植物根的可塑性生长是其适应环境，应对各种逆境胁迫的重要手段之一。脱落酸（abscisic acid，ABA）作为一种重要的逆境激素参与调节植物根的可塑性生长，高浓度ABA抑制主根伸长。目前人们认为ABA调控根生长与生长素、乙烯、活性氧等密切相关，但具体的分子机理尚不明确。本项目发现ABA信号通路中关键转录因子ABF2、ABF3和ABF4可以直接结合生长素合成酶关键基因YUCCA8（YUC8）和YUCCA9（YUC9）启动子并正调控其表达。适量施加YUC抑制剂yucasin能缓解ABA对拟南芥主根生长的抑制，yuc8、yuc9单突变和yuc8yuc9双突变体表现出对ABA抑制主根伸长不敏感的表型，yucQ（yuc3/yuc5/yuc7/yuc8/yuc9）突变体和过量表达YUC8/9植株主根对ABA超敏感，说明YUC8/9参与调控ABA抑制主根生长这一生理过，适度抑制生长素的合成可以减轻ABA对主根生长的抑制。ABF3和ABF4在根尖尤其是分生组织区域有明显表达，与YUC8/YUC9表达有重叠。过表达YUC8/9能部分恢复abf2abf3abf4 突变体对ABA不敏感的表型，说明YUC8/9位于ABFs遗传学下游。过表达ABF2、ABF3或ABF4能显著增加拟南芥主根根长，说明ABFs参与根的生长发育。在yuc8yuc9背景下过表达ABFs使yuc8yuc9对ABA敏感性低的表型减弱，ABFs可能同时调控其他基因介导ABA抑制主根的伸长，同时abf2abf3abf4 突变体中内源生长素信号低。本研究揭示ABFs转录因子在根的生长发育中发挥重要作用，ABA通过ABF2/3/4转录因子直接调控生长素合成基因YUC8/9表达抑制主根的生长，发现了ABA信号与生长素交叉互作调控根的可塑性生长的新机制，为阐明ABA调控植物根生长发育的分子机理奠定一定基础，同时丰富和深化了我们了解植物如何适应多变的环境。.