A Genome-Wide Transcriptional Analysis of Yeast-Hyphal Transition in Candida tropicalis by RNA-Seq

Candida tropicalis is considered as the leading pathogen in nosocomial fungemia and hepatosplenic fungal infections in patients with cancer, particularly in leukemia. The yeast-filament transition is required for virulent infection by Candida. Several studies have explored the genome-wide transcription profile of Candida, however, no report on the transcriptional profile of C. tropicalis under yeast-filament transition has been published.In this study, the transcriptomes of three C. tropicalis isolates with different adhesion and biofilm formation abilities, identified in our previous studies, were analyzed in both the yeast and filament states using RNA-Seq. Differentially expressed genes were found for each isolate during the transition. A total of 115 genes were up- or down- regulated in the two hyphal-producing isolates (ZRCT 4 and ZRCT 45). Among these differentially expressed genes, only two were down-regulated during the yeast-filament transition. Furthermore, six filament-associated genes were up-regulated in the hyphae-producing isolates. According to Candida Hypha Growth Database established in this study, 331 hyphae- related genes were discovered in C. tropicalis. ALS1 and ALS3 were down-regulated and up-regulated, respectively, during filamentous growth of C. tropicalis. These findings proved a better understanding of gene expression dynamics during the yeast-filament transition in C. tropicalis.

热带假丝酵母（Candida tropicalis）被认为是癌症患者（尤其是白血病患者）院内真菌血症与肝脾真菌感染的首要致病菌。假丝酵母的酵母相-菌丝相形态转换（yeast-filament transition）是其实现致病感染的必要条件。目前已有多项研究针对假丝酵母开展全基因组转录谱分析，但尚未见关于热带假丝酵母在酵母相-菌丝相转换过程中转录谱的研究报道。本研究采用RNA测序（RNA-Seq）技术，对本课题组前期筛选获得的3株黏附与生物膜形成能力存在差异的热带假丝酵母分离株，分别在酵母相及菌丝相状态下进行转录组分析。结果显示，各分离株在形态转换过程中均检测到差异表达基因。两株产菌丝分离株（ZRCT 4与ZRCT 45）中共鉴定出115个差异表达基因，其中仅2个基因在酵母相-菌丝相转换过程中呈现下调表达。此外，产菌丝分离株中有6个菌丝相关基因呈现上调表达。依托本研究构建的假丝酵母菌丝生长数据库（Candida Hypha Growth Database），我们在热带假丝酵母中共发现331个菌丝相关基因。在热带假丝酵母的菌丝生长过程中，ALS1与ALS3分别呈现下调与上调表达。本研究结果有助于进一步深化对热带假丝酵母酵母相-菌丝相转换过程中基因表达动态变化的理解。