PTB1控制水稻结实率的分子机制和调控网络

结实率是水稻重要的产量构成因子之一。我们之前利用一个低结实率突变体，成功克隆了一个控制水稻结实率的主效基因PTB1，并证实其通过控制水稻花粉管生长从而正向调控结实率。PTB1基因编码一个RING型E3泛素连接酶，主要在花柱中优势表达，具有促进花粉管在生殖道中生长的深度和数量的功能，从而直接调控水稻结实率的高低。PTB1是首次克隆的水稻结实率关键基因，但其分子机理和调控网络还不清楚。由于PTB1蛋白具有E3泛素连接酶活性，推测其可能特异地泛素化降解了一个对花粉管生长具有抑制作用的负调控因子，从而促进花粉管的生长。因此，获取PTB1的互作蛋白是揭示其控制结实率的遗传机理的关键。本研究拟在上述研究的基础上，运用酵母双杂交、免疫共沉淀等蛋白互作的方法分离PTB1蛋白的直接作用靶标，明确PTB1控制水稻结实率的分子机理；并综合运用转录组学、蛋白组学及功能验证的方法探讨该基因影响结实率的可能调控网络。

Panicle seed-setting rate (PSSR) is one of the most important components of rice grain yield. However, the molecular mechanism underline PSSR regulation remains unknown. We previously cloned a PSSR controlling gene, POLLEN TUBE BLOCKED 1(PTB1), and proved it positively regulates rice PSSR by controlling pollen tube (PT) growth. The PTB1 gene, encoding a RING-type E3 ubiquitin ligase which was expressed preferentially in rice style, promotes PT growth by controlling the amount and growth depth of PTs in style transmitting tract, resulting in a major modulation of rice PSSR. Rice PSSR significantly correlates with natural variation of PTB1 expression and be enhanced by PTB1’s up-regulation. In the present study, we aim to isolate the direct target of PTB1 protein by employing an integrative method of protein-protein interaction, such as Yeast two-hybrid and Co-IP, and to sketch the regulatory network of PTB1 gene by Transcriptomic and protemic analysis. Our results will reveal the molecular mechanism and regulatory network of PTB1 as a key maternal sporophytic factor of PT growth and the principal modulator of rice PSSR, which will give new insights for rice PSSR regulation and immediate implications for rice yield improvement.