构巢曲霉形态建成调节网-SIN途径反向调节子（Suppressor）对于胞质分裂的调控机制

Timely cytokinesis/septation is essential for hyphal growth and conidiation in Aspergillus nidulans. Aspergillus nidulans is an excellent model organism for allowing an unambiguous identification of investigating the regulation features of cytokinesis.Genetic analyses have identified that A. nidulans has components of the septum initiation network (SIN) pathway; one of these, SEPH, is a key player for early events during cytokinesis. However, little is known about how the SEPH kinase cascade is regulated by other components. In this project, to explore the new regulators and the molecular mechanism of the regulation network of SIN,by forward genetics(from mutant to gene identification) combined with reverse genetics( from gene to phenotype) techniques, 116 mutants obtained by UV mutagenesis which suppressed the phenotype of SepH mutant will be further identified.Among them, Sin110 mutation restored septation as well as conidiation in the absence of SEPH.Thus,it clearly provides a direct evidence for the existence of the antagonizing components of the SIN during cytokinesis. Furthermore, we found the defect of Sin110 can be rescued by phosphoribosyl pyrophosphate synthetase 1 (PRPP synthetase)clone.Consequently,the downregulation of AnPRS family can bypass the requirements of the SIN for septum formation and conidiation.The transcription defect of the Anprs gene family accompanied with the reduction of AnPRS activity causes the formation of hyper-septation as well as the restoration of septation and conidiation in the absence of SEPH. Clearly, the timing and positioning of septation is related to AnPRS activity. We will futher analysis how the AnPRS family may act as a heterodimer to exert the biological activity, and the possible relationship between AnPRS and SEPH and between AnPRS and PP2A during cytokinesis in Aspergillus nidulans.

准确地完成胞质分裂/产隔过程是曲霉菌丝生长和无性产孢必需的。当分生孢子萌发，达到一定体积后就能启动细胞隔膜开始网（Septation Initiation Network, SIN），产生隔膜，其中丝-苏氨酸激酶SepH是胞质分裂起始时的关键促动扳机。采用从突变株到基因证实的正向遗传和从基因到表型的反向遗传相结合的方法，本项目将对前期研究用UV突变成功筛选到的SepH突变株的反向调节子116株作进一步的功能验证，发现这些反向调节子中调控胞质分裂的新基因。分析其中一株属于磷酸核糖焦磷酸合成酶（PRPP synthetase，Prs）的同源基因的反向调节子的功能特征，揭示PRS蛋白家族（Prs1，Prs2，Prs,3）的调控酶活力的分子和生化机理。探明 SIN的反向调节子之间以及与SIN途径成员和下游靶之间的调控网，阐明曲霉胞质分裂的调控机制，为丝状真菌的无性繁殖-分生孢子产生提供理论基础。

胞质分裂是细胞分裂细胞质产生两个子细胞的过程，也是有丝分裂的最后一步，维持真核细胞的时序性起着很重要的作用。胞质分裂调节子一直都是细胞生物学家和遗传学家关注的问题。我们选择了对于胞质分裂缺陷忍受能力强的构巢曲霉为研究材料，按计划成功完成了研究目标中要求的任务，筛选到了调节产隔起始网SIN的多个新的反向调节子PRS家族; PP2A-ParA和PP2A-PabA，PomA 和MztA, 并展开了调控网络和机制的研究，尤其是对于SIN 的反向调节子磷酸化酶PomA 和PP2A-ParA的反向调节子MztA进行了深入的功能分析，解析了这些SIN途径的反向调节子是如何和正调节子协同调控胞质分裂，以保证胞质分裂的准确性。本研究成果为进一步揭开胞质分裂和真菌隔膜产生的调控机制提供了新的知识。