Phototropin phosphorylation of ROOT PHOTOTROPISM 2 and its role in mediating phototropism, leaf positioning, and chloroplast accumulation movement in Arabidopsis
Phototropin phosphorylation of ROOT PHOTOTROPISM 2 and its role in mediating phototropism, leaf positioning, and chloroplast accumulation movement in Arabidopsis
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DOI：
10.1111/tpj.16144
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发表时间：
2023-03-07
期刊：
影响因子：
7.2
通讯作者：
Christie，John M.
中科院分区：
文献类型：
--
作者：
Waksman，Thomas;Suetsugu，Noriyuki;Christie，John M.
定向运动影响植物响应和相应地调整其生长以适应主要光环境的能力。质膜相关蛋白ROOT PHOTOTROPISM 2（RPT 2）是参与叶绿体积累运动、叶定位和向光性的关键信号组分，所有这些都由紫外/蓝光激活的AGC激酶phototropin 1和2（phot 1和phot 2）冗余调节。我们最近证明，拟南芥中非嗜光性下胚轴3（NPH 3）/RPT 2样（NRL）家族的成员，包括RPT 2，直接被phot 1磷酸化。然而，RPT 2是否是phot 2的底物，以及RPT 2的phot磷酸化的生物学意义仍有待确定。在这里，我们发现RPT 2在蛋白质C末端区域内的保守丝氨酸残基（S591）处被phot 1和phot 2磷酸化。蓝光触发了14 - 3 - 3蛋白与RPT 2的结合，这与S591作为14 - 3 - 3结合位点一致。S591的突变对RPT 2的质膜定位没有影响，但降低了其叶片定位和向光性的功能。此外，我们的研究结果表明，RPT 2 C末端的S591磷酸化是叶绿体积累运动到低水平蓝光所必需的。总之，这些发现进一步强调了NRL蛋白C末端区域的重要性，以及其磷酸化如何有助于植物中的phot受体信号传导。
Directional movements impact the ability of plants to respond and adjust their growth accordingly to the prevailing light environment. The plasma‐membrane associated protein, ROOT PHOTOTROPISM 2 (RPT2) is a key signalling component involved in chloroplast accumulation movement, leaf positioning, and phototropism, all of which are regulated redundantly by the ultraviolet/blue light‐activated AGC kinases phototropin 1 and 2 (phot1 and phot2). We recently demonstrated that members of the NON‐PHOTOTROPIC HYPOCOTYL 3 (NPH3)/RPT2‐like (NRL) family inArabidopsis thaliana, including RPT2, are directly phosphorylated by phot1. However, whether RPT2 is a substrate for phot2, and the biological significance of phot phosphorylation of RPT2 remains to be determined. Here, we show that RPT2 is phosphorylated by both phot1 and phot2 at a conserved serine residue (S591) within the C‐terminal region of the protein. Blue light triggered the association of 14‐3‐3 proteins with RPT2 consistent with S591 acting as a 14‐3‐3 binding site. Mutation of S591 had no effect on the plasma membrane localization of RPT2 but reduced its functionality for leaf positioning and phototropism. Moreover, our findings indicate that S591 phosphorylation within the C‐terminus of RPT2 is required for chloroplast accumulation movement to low level blue light. Taken together, these findings further highlight the importance of the C‐terminal region of NRL proteins and how its phosphorylation contributes to phot receptor signalling in plants.