拟南芥花粉萌发负调控因子SPG1的生物学意义与分子调控背景

During earlier experiments, our project team found a gene in Arabidopsis that negatively regulates pollen germination. Pollens with this gene knockout do not require boric acid, calcium for germination, and even germinate in anthers under wet conditions. Our earlier results also showed that the gene product accumulates with differential amounts in pollen individuals, regulating pollen germination in a non-synchronized way, a phenomenon we often observe in the in vitro germination experiments. We accordingly named this gene SPG1 (Stepwise Pollen Germination 1). Our database searching result showed that the gene has not been reported before. We speculate that SPG1 gene may contribute to plants to expand the scope of pollination. The current project is designed to study the biological significance of SPG1, the molecular pathways regulating pollen germination by SPG1 and the molecular mechanisms for formation of SPG1 protein accumulation gradients in pollen individuals, using methods including conventional techniques for gene function analysis, microarray and epigenetic analysis. We expect a more in-depth understanding of angiosperm pollen germination through our current project studies.

项目组在前期的实验中发现了一个抑制拟南芥花粉萌发的基因。该基因被敲除后的花粉不需要硼酸、钙离子的诱导即可萌发，甚至在潮湿情况下于花药中萌发。实验结果还显示该基因的产物在花粉个体间形成规律性的丰度差异，调控花粉分批次萌发，即我们经常在体外萌发实验中观察到的不同步萌发。我们据此把这个基因命名为SPG1（Stepwise Pollen Germination 1）。检索结果显示该基因未见报道。我们推测SPG1基因可能有助于植物加大花粉的传播范围。本项目拟利用常规的基因功能分析方法、基因芯片法和表观遗传学分析方法对SPG1基因的生物学意义、下游调控花粉萌发的分子作用途径以及SPG1蛋白在花粉间形成丰度梯度的基因表达调控机制进行深入的实验研究，以期对被子植物花粉萌发的基本现象形成更深入的认识。

长期以来人们对花粉萌发必需的基因及产物进行了较充分的研究，而对花粉不萌发（休眠）的机制知之甚少。本项目通过筛选花粉特异表达但非花粉萌发必需的基因，首次发现了一个抑制花粉萌发的基因JINGUBANG（JGB）（前期曾被命名为SPG1（Stepwise Pllon Germination 1）。JGB通过抑制花粉萌发帮助花粉在潮湿环境中完成授粉，同时也能够促进花粉管中后期伸长使其更具有雄性竞争能力完成受精。JGB有7个WD40结构域，在被子植物中保守。研究表明JGB是一个全新的花粉萌发负调控因子。进一步研究发现jgb花粉中JA含量明显高于Col-0，体外施加茉莉酸甲酯能够打破拟南芥Col-0花粉的休眠，体内JGB通过抑制茉莉酸的合成执行花粉萌发负调控因子的功能。JGB通过和转录因子TCP4相互作用，控制细胞内JA含量和花粉萌发，以保证在潮湿的环境中能传粉。