College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China.
Sci Rep. 2017 Jan 11;7:40279. doi: 10.1038/srep40279.
Arabidopsis exocyst subunit SEC3A has been reported to participate in embryo development. Here we report that SEC3A is involved during pollen germination. A T-DNA insertion in SEC3A leads to an absolute, male-specific transmission defect that can be complemented by the expression of SEC3A coding sequence from the LAT52 promoter or SEC3A genomic DNA. No obvious abnormalities in the microgametogenesis are observed in the sec3a/SEC3A mutant, however, in vitro and in vivo pollen germination are defective. Further studies reveal that the callose, pectin, and cellulose are apparently not deposited at the germination site during pollen germination. SEC3A is expressed ubiquitously, including in pollen grains and pollen tubes. Notably, SEC3A-GFP fusion proteins are specifically recruited to the future pollen germination site. This particular localization pattern is independent of phosphatidylinositol 4,5-bisphosphate (PI-4,5P), although SEC3-HIS fusion proteins are able to bind to several phosphoinositols in vitro. These results suggest that SEC3A plays an important role in the establishment of the polar site for pollen germination.
拟南芥外泌体亚基 SEC3A 已被报道参与胚胎发育。在这里，我们报告 SEC3A 参与花粉萌发。SEC3A 的 T-DNA 插入导致绝对的、雄性特异性的传递缺陷，可通过 LAT52 启动子或 SEC3A 基因组 DNA 表达 SEC3A 编码序列来互补。在 sec3a/SEC3A 突变体中，未观察到小孢子发生的明显异常，然而，体外和体内花粉萌发是有缺陷的。进一步的研究表明，在花粉萌发过程中，在萌发部位显然没有沉积胼胝质、果胶和纤维素。SEC3A 广泛表达，包括在花粉粒和花粉管中。值得注意的是，SEC3A-GFP 融合蛋白被特异性募集到未来的花粉萌发部位。这种特殊的定位模式独立于磷脂酰肌醇 4,5-二磷酸 (PI-4,5P)，尽管 SEC3-HIS 融合蛋白能够在体外结合几种磷酸肌醇。这些结果表明 SEC3A 在花粉萌发的极性位点的建立中发挥重要作用。
