真菌的二型性转换对于其适应环境有重要作用，探索其调控机制具有重要意义。Ras是调控酵母二型性转换的一个关键分子，它通过Ras-MAPK和Ras-cAMP-PKA两条信号传递途径调控菌丝形成。在解脂耶氏酵母中，虽然Ras-MAPK途径能够促进菌丝形成，可是调控程度有限，Ras-cAMP-PKA途径则抑制菌丝形成，与酿酒酵母和白色念珠菌存在差别，推测存在新的Ras调控途径。前期研究中申请人发现转录因子Mhy1作用于Ras下游，对于Ras功能的发挥是必需的。YlRim15蛋白质激酶是另一个作用于Ras信号传递途径下游的分子，前期研究表明它对菌丝形成也具有促进作用。本项目将针对Mhy1和YlRim15进行研究，通过转录组测序和遗传学方法鉴定其控制的靶基因及其受上游分子调控的机制。还计划寻找解脂耶氏酵母菌丝特异性表达基因及新的受Ras控制的基因。本项目对于揭示Ras调控二型性转换的机制具有重要意义。

Dimorphic transition is important for many fungal species to adapt to environmental changes. It is of great importance to investigate the regulation of fungal dimorphism. Ras is a critical player in the regulation of dimorphic transition in yeast. It controls filamentous growth via the Ras-MAPK and the Ras-cAMP-PKA signaling pathways. In the dimorphic yeast Yarrowia lipolytica, the Ras-MAPK pathway promotes hyphal growth. However, its contribution is limited. The Ras-cAMP-PKA pathway, however, represses rather than promotes hyphal growth, which is very different from this pathway’s role in the yeasts Saccharomyces cerevisiae and Candida albicans. It is likely that new Ras signaling pathway may exist in Y. lipolytica. We previously found that the transcription factor Mhy1 acts downstream of Ras and is required for Ras’s function in dimorphic transition. The protein kinase YlRim15 is another molecule that acts downstream of Ras. We found previously that it promotes hyphal growth. In this proposal, we plan to identify the targets of Mhy1 and YlRim15 as well as the regulation of these two factors by upstream regulators by transcriptome sequencing and genetic techniques. We also plan to identify hyphal-specific genes and novel Ras-controlled genes in Y. lipolytica. Our proposed investigation will help understand the mechanism by which Ras controls dimorphic transition.