State Key Laboratory of Crop Stress Biology in Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, PR China.
Fungal Biol. 2012 Sep;116(9):1013-23. doi: 10.1016/j.funbio.2012.07.006. Epub 2012 Jul 27.
Biflagellate zoospores are the major infective agents that initiate plant infection for most Phytophthora species. Once released from sporangia, zoospores swim and use a number of tactic responses to actively target host tissues. However, the molecular mechanisms controlling zoospore development and behaviour are largely unknown. Previous studies have shown that the PnPMA1 gene is highly expressed in zoospores and germinated cysts of Phytophthora parasitica and encodes an atypical plasma membrane H(+)-ATPase containing an insertion of ~155 amino acid residues at the C terminus. Using topology determination we now show that the C-terminal insertion loop in the PnPMA1 protein is located in the extracellular space. To elucidate the biological function of PnPMA1, PnPMA1-deficient transformants were generated by homology-dependent gene silencing and were confirmed by quantitative PCR of PnPMA1 transcripts and detection of associated small interfering RNAs (siRNAs). High levels of PnPMA1 silencing in P. parasitica resulted in production of nonflagellate and large aberrant zoospores, rapid transition from zoospores to cysts, and a decreased germination rate of cysts. These results indicate that PnPMA1 plays important roles in zoospore development.
双鞭毛游动孢子是大多数疫霉菌引发植物感染的主要侵染源。一旦从游动孢子囊中释放出来，游动孢子就会游动，并利用多种策略反应主动靶向宿主组织。然而，控制游动孢子发育和行为的分子机制在很大程度上尚不清楚。先前的研究表明，PnPMA1 基因在寄生疫霉的游动孢子和萌发的胞囊内高度表达，编码一种非典型的质膜 H(+)-ATP 酶，其 C 端有一个约 155 个氨基酸残基的插入。通过拓扑结构测定，我们现在表明，PnPMA1 蛋白的 C 端插入环位于细胞外空间。为了阐明 PnPMA1 的生物学功能，通过同源依赖性基因沉默生成了 PnPMA1 缺陷型转化体，并通过定量 PCR 检测 PnPMA1 转录物和相关的小干扰 RNA（siRNA）进行了确认。寄生疫霉菌中 PnPMA1 的高水平沉默导致产生无鞭毛和大型异常游动孢子、游动孢子快速向胞囊转化以及胞囊的萌发率降低。这些结果表明 PnPMA1 在游动孢子发育中发挥重要作用。
