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CgCmk1 Activates CgRds2 To Resist Low-pH Stress in Candida glabrata.

ABSTRACT: In Candida glabrata, the transcription factor CgRds2 has been previously characterized as a regulator of glycerophospholipid metabolism, playing a crucial role in the response to osmotic stress. Here, we report that CgRds2 is also involved in the response to pH 2.0 stress. At pH 2.0, the deletion of CgRDS2 led to reduced cell growth and survival, by 33% and 57%, respectively, compared with those of the wild-type strain. These adverse phenotypes resulted from the downregulation of genes related to energy metabolism in the Cgrds2? strain at pH 2.0, which led to a 34% reduction of the intracellular ATP content and a 24% decrease in membrane permeability. In contrast, the overexpression of CgRDS2 rescued the growth defect of the Cgrds2? strain and increased cell survival at pH 2.0 by 17% compared with that of the wild-type strain, and this effect was accompanied by significant increases in ATP content and membrane permeability, by 42% and 19%, respectively. Furthermore, we found that the calcium/calmodulin-dependent protein kinase (CaMK) CgCmk1 physically interacts with the PAS domain of CgRds2, and CgCmk1 is required for CgRds2 activation and translocation from the cytoplasm to the nucleus under pH 2.0 stress. Moreover, CgCmk1 is critical for CgRds2 function in resistance to pH 2.0 stress, because cells of the Cgrds2-pas strain with a disrupted CgCmk1-CgRds2 interaction exhibited impaired energy metabolism and membrane permeability at pH 2.0. Therefore, our results indicate that CgCmk1 positively regulates CgRds2 and suggest that they promote resistance to low-pH stress by enhancing energy metabolism and membrane permeability in C. glabrata IMPORTANCE An acidic environment is the main problem in the production of organic acids in C. glabrata The present study reports that the calcium/calmodulin-dependent protein kinase CgCmk1 positively regulates CgRds2 to increase intracellular ATP content, membrane permeability, and resistance to low-pH stress. Hence, the transcription factor CgRds2 may be a potential target for improving the acid stress tolerance of C. glabrata during the fermentation of organic acids. The present study also establishes a new link between the calcium signaling pathway and energy metabolism.

SUBMITTER: Wu C

PROVIDER: S-EPMC7237787 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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CgCmk1 Activates CgRds2 To Resist Low-pH Stress in Candida glabrata.

Wu Chengjin C Zhu Guoxing G Ding Qiang Q Zhou Pei P Liu Liming L Chen Xiulai X

Applied and environmental microbiology 20200519 11

In Candida glabrata, the transcription factor CgRds2 has been previously characterized as a regulator of glycerophospholipid metabolism, playing a crucial role in the response to osmotic stress. Here, we report that CgRds2 is also involved in the response to pH 2.0 stress. At pH 2.0, the deletion of CgRDS2 led to reduced cell growth and survival, by 33% and 57%, respectively, compared with those of the wild-type strain. These adverse phenotypes resulted from the downr ...[more]

PMID: 32245757

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Project description:Candida glabrata is a promising microorganism for organic acid production. The present study aimed to investigate the role of C. glabrata Mediator complex subunit 3 (CgMed3p) in protecting C. glabrata under low-pH conditions. To this end, genes CgMED3A and CgMED3B were deleted, resulting in the double-deletion Cgmed3ABΔ strain. The final biomass and cell viability levels of Cgmed3ABΔ decreased by 64.5% and 35.8%, respectively, compared to the wild-type strain results at pH 2.0. In addition, lack of CgMed3ABp resulted in selective repression of a subset of genes in the lipid biosynthesis and metabolism pathways. Furthermore, C18:1, lanosterol, zymosterol, fecosterol, and ergosterol were 13.2%, 80.4%, 40.4%, 78.1%, and 70.4% less abundant, respectively, in the Cgmed3ABΔ strain. In contrast, the concentration of squalene increased by about 44.6-fold. As a result, membrane integrity, rigidity, and H+-ATPase activity in the Cgmed3ABΔ strain were reduced by 62.7%, 13.0%, and 50.3%, respectively. In contrast, overexpression of CgMED3AB increased the levels of C18:0, C18:1, and ergosterol by 113.2%, 5.9%, and 26.4%, respectively. Moreover, compared to the wild-type results, dry cell weight and pyruvate production increased, irrespective of pH buffering. These results suggest that CgMED3AB regulates membrane composition, which in turn enables cells to tolerate low-pH stress. We propose that regulation of CgMed3ABp may provide a novel strategy for enhancing low-pH tolerance and increasing organic acid production by C. glabrataIMPORTANCE The objective of this study was to investigate the role of Candida glabrata Mediator complex subunit 3 (CgMed3ABp) and its regulation of gene expression at low pH in C. glabrata We found that CgMed3ABp was critical for cellular survival and pyruvate production during low-pH stress. Measures of the levels of plasma membrane fatty acids and sterol composition indicated that CgMed3ABp could play an important role in regulating homeostasis in C. glabrata We propose that controlling membrane lipid composition may enhance the robustness of C. glabrata for the production of organic acids.

Project description:Candida glabrata is a high-performance microbial cell factory for the production of organic acids. To elucidate the role of the C. glabrata Mediator tail subunit Med2 (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 a cell growth decrease of 26.1% and a survival decrease of 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 the low-pH stress response in C. glabrata.

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CgCmk1 Activates CgRds2 To Resist Low-pH Stress in Candida glabrata.

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<i>Cg</i>Cmk1 Activates <i>Cg</i>Rds2 To Resist Low-pH Stress in Candida glabrata.

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