低磷诱导的植物根际酸化反应可活化根际的不溶磷、促进土壤磷素的高效利用；但低磷诱导根际酸化反应的分子机制至今还不清楚。我们利用pH指示剂显色法，筛选得到一株低磷诱导根际酸化增强的拟南芥突变体p455，该突变体具有较强的低磷和不溶磷胁迫适应能力；P455基因编码一个具有IQD结构域的微管相关蛋白，该蛋白可与CAM7互作，负调控细胞质膜H+-ATPase的含量、活性和质子分泌；P455::GFP融合蛋白和FM4-64共定位分析表明，微管相关的P455蛋白在细胞质膜和内吞膜泡上也有分布。推测，P455可能介导低磷信号，并在蛋白水平上负调控质膜H+-ATPase的活性和根际酸化反应。本项目拟利用不同的方法筛选P455互作蛋白，分析P455信号通路组分和P455调节质膜H+-ATPase的分子机制；利用荧光标记和单分子荧光等方法，分析微管骨架和胞质钙信号在P455调节根际酸化反应中的作用。

Phosphorus (P) is an essential macronutrient. One unique characteristic of P is its low availability due to slow diffusion and high fixation in soils. This means that P can be a major limiting factor for plant growth. As a consequence of persistent P-limitations, plants have evolved a wide range of P acquisition strategies. Rhizosphere acidification through enhanced exudation of organic acids and protons could improve available of phosphate in the soil. But the mechanism of rhizosphere acidification induced by low phosphate remains unclear. p455 is an mutant of enhanced rhizosphere acidification induced by low phosphate in Arabidopsis, which has the adaptation to the stress of low or insoluble phosphorus . P455 gene encodes a microtubule-associated protein with an IQ-domain. P455 could interact with CAM7, and negatively regulate the activity and amount of plasma membrane H+-ATPase. The analyzing for co-localization of P455::GFP fusion protein and FM4-64 indicates that P455 also locates in the plasma membrane and endocytic vesicle. These results indicate that P455 could mediate low phosphate signals and negatively regulate the activity and amount of plasma membrane H+-ATPase. In this project, we will identify the molecular mechanism for the regulation of the plasma membrane H+-ATPase activity and low phosphate induced rhizosphere acidification by microtubule-associated P455.