Candida glabrata Yap6 Recruits Med2 To Alter Glycerophospholipid Composition and Develop Acid pH Stress Resistance

Abstract

Candida glabrata is a well-performance microbial cell factories for the production of organic acids. To elucidate the role of the Mediator tail subunit CgMed2 at pH 2.0, we deleted or overexpressed CgMed2 and used transcriptome analysis to identify genes that are regulated by CgMed2. At pH 2.0, the deletion of CgMed2 resulted in cell growth decrease by 26.1% and survival decrease by 32.3%. Overexpression of CgMed2 increased cell growth by 12.4% and cell survival by 5.9% compared to the wild-type strain. Transcriptome and phenotypic analyses identified CgYap6 as a transcription factor involved in acid pH stress tolerance. Deletion of CgYap6 caused growth defects, whereas its overexpression enhanced cell growth at pH 2.0. Furthermore, total glycerophospholipid content and membrane integrity decreased by 33.4% and 21.8%, respectively, in the CgMed2Δ strain; however, overexpression of CgMed2 increased the total glycerophospholipid content and membrane integrity by 24.7% and 12.1%, respectively, compared with those of the wild-type strain at pH 2.0. These results demonstrated that, under acid pH stress, CgMed2 physically interacts with CgYap6, which translocates from the cytoplasm to the nucleus after being phosphorylated by the protein kinase CgYak1. Once in the nucleus, CgYap6 recruits CgMed2 to express glycerophospholipid-related genes. Our study elucidated the function of CgMed2 under acid pH stress and provides a potential strategy to equip Candida glabrata with low pH resistance during organic acid fermentation. IMPORTANCE This study investigated the function of the Mediator tail subunit CgMed2 in C. glabrata under low pH stress. The protein kinase CgYak1 activates CgYap6 for the recruitment of CgMed2, which in turn increases glycerophospholipid content and membrane integrity to confer low pH stress tolerance. This study establishes a new link between the Mediator tail subunit and transcription factors. Overall, these findings indicate that CgMed2 is a novel target to induce low pH stress response in C. glabrata.

Dynamic regulation of membrane integrity to enhance l‐malate stress tolerance in Candida glabrata

“…Furthermore, it was found that dynamic regulation of Cg Med16 could not significantly improve the tolerance to l ‐malate stress (Figure S8). The reason is that mediators act as a bridge connect transcription factors and gene expression (Jeronimo & Robert, 2017; Menezes et al, 2017; Thakur et al, 2009), which is an indirect model to regulate gene expression (Kim & Gross, 2013; Zhou et al, 2020). Therefore, compared with overexpressed Cg Med16, the overexpression of transcription factors Cg YAP3 and Cg USV1 can better improve the tolerance of the strain.…”

“…Furthermore, our previous studies showed that transcription factors play an important role in tolerance to acid stress in C. glabrata. For instance, by recruiting the mediator CgMed2, transcription factor CgYap6 activates glycerophospholipid genes to enhance membrane integrity against low pH stress (Zhou et al, 2020), and overexpressing the transcription factor CgCrz1 to improve membrane integrity led to improved resistance to low pH stress (Yan et al, 2016). In this study, A DTS was constructed based on promoter P cgr-10 to enhance the robustness and productive capacity of C. glabrata.…”

“…The Tail module comprises five subunits, including Med2, Med3, Med5, Med15, and Med16. Some of these Tail subunits, such as Med2 (Dai et al, 2018; Zhou et al, 2020), Med3 (Lin et al, 2017), and Med15 (Qi et al, 2017; Thakur et al, 2009), play key roles in the resistance to environmental stress. Med16, as part of the tail module, could interact with transcription factors to regulate the transcription of nearly all RNA polymerase II‐dependent genes in yeast (Soutourina, 2018).…”