Liu Huiquan, Zhang Shijie, Ma Jiwen, Dai Yafeng, Li Chaohui, Lyu Xueliang, Wang Chenfang, Xu Jin-Rong
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest Agriculture and Forestry University, Yangling, Shaanxi, China; Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America.
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest Agriculture and Forestry University, Yangling, Shaanxi, China.
PLoS Pathog. 2015 Jun 17;11(6):e1004913. doi: 10.1371/journal.ppat.1004913. eCollection 2015 Jun.
Eukaryotic cell cycle involves a number of protein kinases important for the onset and progression through mitosis, most of which are well characterized in the budding and fission yeasts and conserved in other fungi. However, unlike the model yeast and filamentous fungi that have a single Cdc2 essential for cell cycle progression, the wheat scab fungus Fusarium graminearum contains two CDC2 orthologs. The cdc2A and cdc2B mutants had no obvious defects in growth rate and conidiation but deletion of both of them is lethal, indicating that these two CDC2 orthologs have redundant functions during vegetative growth and asexual reproduction. However, whereas the cdc2B mutant was normal, the cdc2A mutant was significantly reduced in virulence and rarely produced ascospores. Although deletion of CDC2A had no obvious effect on the formation of penetration branches or hyphopodia, the cdc2A mutant was limited in the differentiation and growth of infectious growth in wheat tissues. Therefore, CDC2A plays stage-specific roles in cell cycle regulation during infectious growth and sexual reproduction. Both CDC2A and CDC2B are constitutively expressed but only CDC2A was up-regulated during plant infection and ascosporogenesis. Localization of Cdc2A- GFP to the nucleus but not Cdc2B-GFP was observed in vegetative hyphae, ascospores, and infectious hyphae. Complementation assays with chimeric fusion constructs showed that both the N- and C-terminal regions of Cdc2A are important for its functions in pathogenesis and ascosporogenesis but only the N-terminal region is important for its subcellular localization. Among the Sordariomycetes, only three Fusarium species closely related to F. graminearum have two CDC2 genes. Furthermore, F. graminearum uniquely has two Aurora kinase genes and one additional putative cyclin gene, and its orthologs of CAK1 and other four essential mitotic kinases in the budding yeast are dispensable for viability. Overall, our data indicate that cell cycle regulation is different between vegetative and infectious hyphae in F. graminearum and Cdc2A, possibly by interacting with a stage-specific cyclin, plays a more important role than Cdc2B during ascosporogenesis and plant infection.
真核细胞周期涉及许多对有丝分裂的起始和进程至关重要的蛋白激酶，其中大多数在芽殖酵母和裂殖酵母中已得到充分表征，并在其他真菌中保守。然而，与对细胞周期进程至关重要的单一Cdc2的模式酵母和丝状真菌不同，小麦赤霉病菌禾谷镰刀菌含有两个CDC2直系同源物。cdc2A和cdc2B突变体在生长速率和产孢方面没有明显缺陷，但两者都缺失是致死的，这表明这两个CDC2直系同源物在营养生长和无性繁殖过程中具有冗余功能。然而，虽然cdc2B突变体正常，但cdc2A突变体的毒力显著降低，很少产生子囊孢子。虽然缺失CDC2A对穿透分支或附着胞的形成没有明显影响，但cdc2A突变体在小麦组织中的侵染性生长的分化和生长方面受到限制。因此，CDC2A在侵染性生长和有性生殖过程中的细胞周期调控中发挥阶段特异性作用。CDC2A和CDC2B都是组成型表达的，但只有CDC2A在植物感染和子囊孢子形成过程中上调。在营养菌丝、子囊孢子和侵染性菌丝中观察到Cdc2A - GFP定位于细胞核，而Cdc2B - GFP则没有。用嵌合融合构建体进行的互补试验表明，Cdc2A的N端和C端区域对其在致病和子囊孢子形成中的功能都很重要，但只有N端区域对其亚细胞定位很重要。在粪壳菌纲中，只有三种与禾谷镰刀菌密切相关的镰刀菌物种有两个CDC2基因。此外，禾谷镰刀菌独特地有两个极光激酶基因和一个额外的假定细胞周期蛋白基因，其在芽殖酵母中CAK1和其他四个必需的有丝分裂激酶的直系同源物对生存力是可有可无的。总体而言，我们的数据表明，禾谷镰刀菌营养菌丝和侵染性菌丝之间的细胞周期调控不同，并且Cdc2A可能通过与阶段特异性细胞周期蛋白相互作用，在子囊孢子形成和植物感染过程中比Cdc2B发挥更重要的作用。
