State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, P. R. China.
Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
Plant Physiol. 2021 May 27;186(1):330-343. doi: 10.1093/plphys/kiab049.
Pollen development is a key process for the sexual reproduction of angiosperms. The Golgi plays a critical role in pollen development via the synthesis and transport of cell wall materials. However, little is known about the molecular mechanisms underlying the maintenance of Golgi integrity in plants. In Arabidopsis thaliana, syntaxin of plants (SYP) 3 family proteins SYP31 and SYP32 are the only two Golgi-localized Qa-soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) with unknown endogenous functions. Here, we demonstrate the roles of SYP31 and SYP32 in modulating Golgi morphology and pollen development. Two independent lines of syp31/+ syp32/+ double mutants were male gametophytic lethal; the zero transmission rate of syp31 syp32 mutations was restored to largely normal levels by pSYP32:SYP32 but not pSYP32:SYP31 transgenes, indicating their functional differences in pollen development. The initial arrest of syp31 syp32 pollen occurred during the transition from the microspore to the bicellular stage, where cell plate formation in pollen mitosis I (PMI) and deposition of intine were abnormal. In syp31 syp32 pollen, the number and length of Golgi cisterna were significantly reduced, accompanied by many surrounding vesicles, which could be largely attributed to defects in anterograde and retrograde trafficking routes. SYP31 and SYP32 directly interacted with COG3, a subunit of the conserved oligomeric Golgi (COG) complex and were responsible for its Golgi localization, providing an underlying mechanism for SYP31/32 function in intra-Golgi trafficking. We propose that SYP31 and SYP32 play partially redundant roles in pollen development by modulating protein trafficking and Golgi structure.
花粉发育是被子植物有性生殖的关键过程。高尔基体通过细胞壁物质的合成和运输在花粉发育中起关键作用。然而，植物中高尔基体完整性维持的分子机制知之甚少。在拟南芥中，植物 SNARE（SYP）3 家族蛋白 SYP31 和 SYP32 是唯二两个定位于高尔基体的 Qa 可溶性 N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE），但其内源性功能未知。在这里，我们证明了 SYP31 和 SYP32 在调节高尔基体形态和花粉发育中的作用。两个独立的 syp31/+ syp32/+ 双突变体系雄性配子体致死；syp31 syp32 突变的零传递率通过 pSYP32:SYP32 而非 pSYP32:SYP31 转基因恢复到大致正常水平，表明它们在花粉发育中的功能差异。syp31 syp32 花粉的最初停滞发生在从小孢子到二细胞阶段的过渡时期，花粉有丝分裂 I（PMI）中的细胞板形成和胞壁内层的沉积异常。在 syp31 syp32 花粉中，高尔基体潴泡的数量和长度显著减少，伴随许多周围小泡，这主要归因于顺行和逆行运输途径的缺陷。SYP31 和 SYP32 直接与 COG3 相互作用，COG3 是保守寡聚高尔基体（COG）复合物的一个亚基，负责其高尔基体定位，为 SYP31/32 在高尔基体内部运输中的功能提供了潜在的机制。我们提出，SYP31 和 SYP32 通过调节蛋白质运输和高尔基体结构在花粉发育中发挥部分冗余作用。
