拟南芥ABC转运蛋白P2SA1介导强蓝光诱导下胚轴向光弯曲的机制分析

Blue light receptor PHOT1 and PHOT2 not only perform function in regulating high blue light induced Arabidopsis hypocotyls phototropism but also regulate proteins such as NPH3, RPT2, PKSs and intracellular Ca2+ changes. Funded by Youth Foundation of NSFC, we screened an ABC transporter P2SA1 (PHOT2 Signaling Associated 1), which affected the transport and lateral gradient distribution of auxin and specifically regulated hypocotyl bending under high blue light. Our results also indicated that high blue light induced the expression and phosphorylation of P2SA1, and the 82th and 88th serine may be the regulated action sites. However, the corresponding detailed mechanism refer to P2SA1, such as how to modulate its activity, the effect on auxin transport and formation of lateral auxin gradient as well as the role in integrating and differentiating the blue light signal induced by PHOT1 and PHOT2, remains to be elucidated. With multidisciplinary research technology, we will research the effects of P2SA1 phosphorylation induced by high blue light on its activity and auxin transportation, explore the relationship between P2SA1 and NPH3, RPT2 and PKSs, which mediate phototropism under high blue light, analyses the function of P2SA1 in regulating intracellular Ca2+ changes to elucidate the mechanism of upstream signals perception and downstream substrate selection during P2SA1 functioning. This study may provide clue for understanding the molecular mechanism of P2SA1 in signal integration and distinction in response to high blue light.

蓝光受体向光素PHOT1和PHOT2调节强蓝光诱导的拟南芥下胚轴向光弯曲，该信号通路涉及NPH3、RPT2和PKSs蛋白及胞内Ca2+ 浓度变化的调控。我们前期筛选到一个ABC转运蛋白P2SA1，定位于细胞质膜，受强蓝光诱导表达和磷酸化修饰，介导生长素在下胚轴中的转运和侧向梯度形成，特异调节强蓝光诱导的下胚轴向光弯曲。然而P2SA1的活性调节模式、其影响生长素侧向梯度形成的机理，以及区分和整合PHOT1和PHOT2介导蓝光信号的机制等并不清楚。本项目拟综合多学科的研究技术，系统分析强蓝光对P2SA1活性调控与生长素转运和侧向梯度形成的作用机制，探讨P2SA1与强蓝光信号传递途径中多种关键组分的调控关系，明确P2SA1在强蓝光诱导胞内Ca2+变化中的功能，解析P2SA1上游信号感受和下游底物选择机制。该研究有望揭示PHOT1和PHOT2介导植物强蓝光应答过程中信号的整合与区分的基本机制。

项目研究拟南芥ABC转运蛋白P2SA1参与调节下胚轴向光弯曲的机制，发现：1.强蓝光可以诱导P2SA1蛋白的第612和640位丝氨酸发生磷酸化而被激活；2.蓝光受体phot1和phot2感受强蓝光诱导蛋白P2SA1磷酸化受PKS1蛋白调节；3.同位素示踪分析显示，P2SA1作为ABC转运蛋白并不直接转运生长素和糖，而是通过转运长链脂肪酸正调节下胚轴和子叶表面蜡质合成，增强拟南芥幼苗抵御水涝能力；4.蛋白P2SA1缺失，拟南芥表现下胚轴和子叶表面蜡质合成受阻，抵御水涝能力降低，诱使H2O2过量合成积累，抑制下胚轴向光性生长。项目提出并证实phot1感受强蓝光促使蛋白质NPH3从细胞质膜解离，蓝光诱导的phot2和RPT2快速表达调节NPH3细胞质膜再定位，实现植物下胚轴向光第一次弯曲到第二次弯曲的快速切换。明确了phot2介导下胚轴弯曲被JAC1与RPT2互作协同抑制的机制。该研究初步揭示了phot1和phot2差异调节拟南芥强蓝光应答的整合与区分机制。