独脚金内酯参与miR399调控水稻根系生长及磷吸收转运的机制

Rice (Oryza sativa L.) is one of the main food crops in China. The improvement of its output depends on the fertilizer input. Improved the ability of nutrient absorption is of great significance for improving nutrient utilization in rice. The root system is fundamentally important for rice to efficiently obtain nutrients. Root growth is regulated by environmental conditions, such as P levels in soil. At present, it has been proved that miR399 and its target gene PHO2 have important soles in regulating P uptake and transport in rice. However, it remains unclear whether miR399 and PHO2 mediate root growth in response to varying levels of P supply. In this project, STTM399 mutants and PHO2 over-expressing rice plants will be used as material to study. To determine the molecular mechanisms of miR399 and PHO2 in regulation of root growth and SL synthesis. The changes of root system and strigolactones (SLs) exudates from root, and the expression of SL-synthesis and SL-signalling genes in response to varying levels of P supply will be analysed in STTM399 mutants and PHO2 over-expressing plants. Application of the SL analogue and synthesis inhibitor to reveal the soles of SLs in regulation of root growth, P uptake and transport by miR399 and PHO2. Rice plants that contains DR5::GFP will be used to understand the relation between SLs and auxin in regulating root growth.

水稻是我国的主要粮食作物之一，其产量的提高依赖于肥料的投入，改善水稻的养分吸收能力对于提高养分利用率具有重要意义。理想的根系性状是水稻高效吸收养分的基础，而水稻的根系形态和土壤中的磷水平密切相关。目前miR399及其靶基因PHO2已经被证实参与了水稻对磷素的吸收和转运，而它们是否参与了磷调控水稻根系的生长还不清楚。本课题以水稻STTM399突变体和PHO2超表达材料为试材，研究不同磷浓度下水稻根系形态和根系分泌物中独脚金内酯的变化及其合成和信号转导相关基因表达，阐明miR399和PHO2调控水稻根系生长和独脚金内酯合成的分子机制；研究根系形态和磷的吸收转运对外源独脚金内酯和合成抑制剂的响应，揭示独脚金内酯参与miR399和PHO2调控水稻根系生长和磷吸收转运的机制；采用DR5::GFP转基因材料，揭示独脚金内酯和生长素在miR399和PHO2调控水稻根系生长的互作机制。

水稻是我国的主要粮食作物之一，其产量的提高依赖于磷肥的投入，挖掘水稻的吸磷潜力对于提高磷肥利用率具有重要意义。理想的根系性状是水稻高效吸收磷素的重要基础。OsmiR399能够通过其靶基因OsPHO2调控磷的吸收，转运和再分配。但OsPHO2调控水稻根系生长发育的机制仍不清楚。研究结果表明，与野生型(WT)相比，在正常供磷（NP）和低磷（LP）处理下，水稻OsmiR399过表达材料和ospho2突变体的种子根（SR）长度和侧根（LR）数显著降低，表明OsPHO2参与了不同磷浓度调控水稻根系生长发育的过程。外源施加IAA和GR24（独角金内酯类似物）能够诱导了OsPHO2的表达。而ospho2突变体的根中IAA含量明显低于WT，同时根系中的OsPIN1b蛋白水平显著低于野生型，且ospin1b突变体与ospho2突变体具有相似的根系表型。OsPHO2基因的突变能够上调独脚金内酯信号转导基因D3的表达，但并不影响独脚金内酯的合成。外源施加GR24降低了根系中OsPIN1b的蛋白水平。但OsD3与OsPIN1b并不存在直接的蛋白互作。这些结果表明，miR399及其靶基因OsPHO2参与磷调控水稻根系生长发育的过程，且独脚金内酯和生长素在这个过程中起着重要的作用。