ZmSTK1 and ZmSTK2, encoding receptor-like cytoplasmic kinase, are involved in maize pollen development with additive effect

Pollen germination and pollen tube growth are important physiological processes of sexual reproduction (有性生殖) of plants and also are involved in signal transduction. Our previous study reveals that ZmSTK1 and ZmSTK2 are two receptor-like cytoplasmic kinases (RLCK; 类受体胞浆激酶) homologs in Zea mays as members of receptor-like protein kinase (RLK) subfamily, sharing 86% identity at the amino acid level. Here, we report that ZmSTK1 and ZmSTK2, expressed at late stages of pollen development, regulate maize pollen development with additive effect (加性效应). ZmSTK1 or ZmSTK2 mutation exhibited severe pollen transmission deficiency, which thus influenced pollen fertility. Moreover, the kinase domains of ZmSTKs were cross-interacted with C-terminus of enolases (烯醇酶) detected by co-immunoprecipitation (Co-IP; 免疫共沉淀) and yeast two-hybrid system (Y2H), respectively. Further, the detective ZmSTK1 or ZmSTK2 was associated with decreased activity of enolases and also reduced downstream metabolite contents, which enolases are involved in glycolytic pathway (糖酵解途径), such as phosphoenolpyruvate (PEP; 磷酸烯醇式丙酮酸), pyruvate (丙酮酸), ADP/ATP, starch (淀粉), glucose, sucrose and fructose (果糖). This study reveals that ZmSTK1 and ZmSTK2 regulate maize pollen development and indirectly participate in glycolytic pathway.

花粉萌发和花粉管生长是植物有性生殖过程中非常重要的生理过程，并参与到了信号转导网络中。作者先前的研究显示ZmSTK1和ZmSTK2是两个玉米中的类受体胞浆激酶RLCK两个同源基因，是类受体激酶亚家族中的成员，这两个基因在蛋白水平的一致性为86%。本文报道了ZmSTK1和ZmSTK2基因在花粉发育的后期表达，并在调控玉米花粉发育上存在加性效应。ZmSTK1或者ZmSTK2基因的突变体会存在严重的花粉传输缺陷，进而影响到花粉的育性。此外，通过免疫共沉淀和酵母双杂等试验技术鉴定了ZmSTK的激酶结构域与烯醇酶的C端交叉互作。另外，ZmSTK1或者ZmSTK2与烯醇酶活性的减弱相关，并且会减少下游的代谢成分，烯醇酶会参与到糖酵解途径，比如磷酸烯醇式丙酮酸、丙酮酸、ADP/ATP、淀粉、葡萄糖、蔗糖和果糖。本文的研究揭示了ZmSTK1和ZmSTK2基因调控玉米的花粉发育，并直接参与到糖酵解途径中。

doi: 10.1111/pbi.12880