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Integration of Posttranscriptional Gene Networks into Metabolic Adaptation and Biofilm Maturation in Candida albicans.

Verma-Gaur J, Qu Y, Harrison PF, Lo TL, Quenault T, Dagley MJ, Bellousoff M, Powell DR, Beilharz TH, Traven A - PLoS Genet. (2015)

Bottom Line: The extracellular matrix is critical for antifungal resistance and immune evasion, and yet of all biofilm maturation pathways extracellular matrix biogenesis is the least understood.We propose a model in which the hypoxic biofilm environment is sensed by regulators such as Ccr4 to orchestrate metabolic adaptation, as well as the regulation of extracellular matrix production by impacting on the expression of matrix-related cell wall genes.Therefore metabolic changes in biofilms might be intimately linked to a key biofilm maturation mechanism that ultimately results in untreatable fungal disease.

View Article: PubMed Central - PubMed

Affiliation: Infection and Immunity Program, Biomedicine Discovery Institute and the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.

ABSTRACT
The yeast Candida albicans is a human commensal and opportunistic pathogen. Although both commensalism and pathogenesis depend on metabolic adaptation, the regulatory pathways that mediate metabolic processes in C. albicans are incompletely defined. For example, metabolic change is a major feature that distinguishes community growth of C. albicans in biofilms compared to suspension cultures, but how metabolic adaptation is functionally interfaced with the structural and gene regulatory changes that drive biofilm maturation remains to be fully understood. We show here that the RNA binding protein Puf3 regulates a posttranscriptional mRNA network in C. albicans that impacts on mitochondrial biogenesis, and provide the first functional data suggesting evolutionary rewiring of posttranscriptional gene regulation between the model yeast Saccharomyces cerevisiae and C. albicans. A proportion of the Puf3 mRNA network is differentially expressed in biofilms, and by using a mutant in the mRNA deadenylase CCR4 (the enzyme recruited to mRNAs by Puf3 to control transcript stability) we show that posttranscriptional regulation is important for mitochondrial regulation in biofilms. Inactivation of CCR4 or dis-regulation of mitochondrial activity led to altered biofilm structure and over-production of extracellular matrix material. The extracellular matrix is critical for antifungal resistance and immune evasion, and yet of all biofilm maturation pathways extracellular matrix biogenesis is the least understood. We propose a model in which the hypoxic biofilm environment is sensed by regulators such as Ccr4 to orchestrate metabolic adaptation, as well as the regulation of extracellular matrix production by impacting on the expression of matrix-related cell wall genes. Therefore metabolic changes in biofilms might be intimately linked to a key biofilm maturation mechanism that ultimately results in untreatable fungal disease.

No MeSH data available.


Related in: MedlinePlus

Posttranscriptional regulation of the mitochondrial ribosome and the COX genes by carbon source and Puf3 in S. cerevisiae.Decay of the indicated mRNAs was measured in wild type and puf3Δ strains grown in glucose (A) or lactate (B) following transcriptional repression at 37°C. The decay curves and half-life (T1/2) were calculated as in Fig 4. The data are shown as the average and standard error of 2–4 biological replicates.
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pgen.1005590.g005: Posttranscriptional regulation of the mitochondrial ribosome and the COX genes by carbon source and Puf3 in S. cerevisiae.Decay of the indicated mRNAs was measured in wild type and puf3Δ strains grown in glucose (A) or lactate (B) following transcriptional repression at 37°C. The decay curves and half-life (T1/2) were calculated as in Fig 4. The data are shown as the average and standard error of 2–4 biological replicates.

Mentions: Our results were somewhat surprising in light of previous publications in S. cerevisiae that showed that: a) transcripts encoding mitochondrial proteins are stabilized during growth of a wild type strain in non-fermentable carbon sources compared to growth in glucose, and b) Puf3 represses mRNA stability only in glucose, but not in non-fermentable carbon sources [36,45]. While previous studies in S. cerevisiae used several non-fermentable carbon sources, lactate was not directly tested. To test the effects of lactate in S. cerevisiae, we made use of a strain that carries an RNA polymerase II temperature sensitive mutation (rpb1-1) which allows for repression of transcription at 37°C (wild type and puf3 mutant, described in [36]). Similarly to C. albicans, in S. cerevisiae deletion of PUF3 had a stabilizing effect in both glucose and lactate on two transcripts that encode cytochrome c oxidase assembly factors: COX17 and COX23 (Fig 5). Moreover, in wild type cells the half-life was similar for these two transcripts in glucose and lactate media (compare Fig 5A and 5B). The situation with the mRNA encoding the mitochondrial ribosomal subunit MRPL25 was different. Firstly, unlike in C. albicans, in S. cerevisiae the MRPL25 transcript was stabilized in lactate compared to glucose in wild type cells (compare Fig 5A and 5B). Secondly, while deletion of PUF3 had a stabilizing effect in glucose (albeit less pronounced than what is seen in C. albicans), in lactate the half-life for MRPL25 was the same in wild type and puf3Δ mutant cells (Fig 5A and 5B). For two other transcripts encoding mitochondrial ribosomal proteins, MRP21 and MRPL11, in wild type cells mRNAs decay was also fast in glucose media and slower in lactate, although stabilization in lactate was less pronounced than what was observed for MRPL25 (Fig 5A and 5B, bottom two graphs). Deletion of PUF3 resulted in stabilization of MRP21 and MRPL11 in glucose (Fig 5A), and also some stabilization, particularly for MRPL11, was observable in lactate (Fig 5B). As controls, we assayed three transcripts with mitochondrial functions, which do not contain Puf3 binding sites in the 3′ UTR: MMF1, FUM1 and OAC1. Deletion of PUF3 had no effect on the decay of these three transcripts in either glucose or lactate (S5 Fig). Therefore, mRNAs that do not contain a Puf3 binding motif do not respond to deletion of PUF3, suggesting that the observed stabilization of the COX and MRP genes in the puf3Δ mutant is specific.


Integration of Posttranscriptional Gene Networks into Metabolic Adaptation and Biofilm Maturation in Candida albicans.

Verma-Gaur J, Qu Y, Harrison PF, Lo TL, Quenault T, Dagley MJ, Bellousoff M, Powell DR, Beilharz TH, Traven A - PLoS Genet. (2015)

Posttranscriptional regulation of the mitochondrial ribosome and the COX genes by carbon source and Puf3 in S. cerevisiae.Decay of the indicated mRNAs was measured in wild type and puf3Δ strains grown in glucose (A) or lactate (B) following transcriptional repression at 37°C. The decay curves and half-life (T1/2) were calculated as in Fig 4. The data are shown as the average and standard error of 2–4 biological replicates.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608769&req=5

pgen.1005590.g005: Posttranscriptional regulation of the mitochondrial ribosome and the COX genes by carbon source and Puf3 in S. cerevisiae.Decay of the indicated mRNAs was measured in wild type and puf3Δ strains grown in glucose (A) or lactate (B) following transcriptional repression at 37°C. The decay curves and half-life (T1/2) were calculated as in Fig 4. The data are shown as the average and standard error of 2–4 biological replicates.
Mentions: Our results were somewhat surprising in light of previous publications in S. cerevisiae that showed that: a) transcripts encoding mitochondrial proteins are stabilized during growth of a wild type strain in non-fermentable carbon sources compared to growth in glucose, and b) Puf3 represses mRNA stability only in glucose, but not in non-fermentable carbon sources [36,45]. While previous studies in S. cerevisiae used several non-fermentable carbon sources, lactate was not directly tested. To test the effects of lactate in S. cerevisiae, we made use of a strain that carries an RNA polymerase II temperature sensitive mutation (rpb1-1) which allows for repression of transcription at 37°C (wild type and puf3 mutant, described in [36]). Similarly to C. albicans, in S. cerevisiae deletion of PUF3 had a stabilizing effect in both glucose and lactate on two transcripts that encode cytochrome c oxidase assembly factors: COX17 and COX23 (Fig 5). Moreover, in wild type cells the half-life was similar for these two transcripts in glucose and lactate media (compare Fig 5A and 5B). The situation with the mRNA encoding the mitochondrial ribosomal subunit MRPL25 was different. Firstly, unlike in C. albicans, in S. cerevisiae the MRPL25 transcript was stabilized in lactate compared to glucose in wild type cells (compare Fig 5A and 5B). Secondly, while deletion of PUF3 had a stabilizing effect in glucose (albeit less pronounced than what is seen in C. albicans), in lactate the half-life for MRPL25 was the same in wild type and puf3Δ mutant cells (Fig 5A and 5B). For two other transcripts encoding mitochondrial ribosomal proteins, MRP21 and MRPL11, in wild type cells mRNAs decay was also fast in glucose media and slower in lactate, although stabilization in lactate was less pronounced than what was observed for MRPL25 (Fig 5A and 5B, bottom two graphs). Deletion of PUF3 resulted in stabilization of MRP21 and MRPL11 in glucose (Fig 5A), and also some stabilization, particularly for MRPL11, was observable in lactate (Fig 5B). As controls, we assayed three transcripts with mitochondrial functions, which do not contain Puf3 binding sites in the 3′ UTR: MMF1, FUM1 and OAC1. Deletion of PUF3 had no effect on the decay of these three transcripts in either glucose or lactate (S5 Fig). Therefore, mRNAs that do not contain a Puf3 binding motif do not respond to deletion of PUF3, suggesting that the observed stabilization of the COX and MRP genes in the puf3Δ mutant is specific.

Bottom Line: The extracellular matrix is critical for antifungal resistance and immune evasion, and yet of all biofilm maturation pathways extracellular matrix biogenesis is the least understood.We propose a model in which the hypoxic biofilm environment is sensed by regulators such as Ccr4 to orchestrate metabolic adaptation, as well as the regulation of extracellular matrix production by impacting on the expression of matrix-related cell wall genes.Therefore metabolic changes in biofilms might be intimately linked to a key biofilm maturation mechanism that ultimately results in untreatable fungal disease.

View Article: PubMed Central - PubMed

Affiliation: Infection and Immunity Program, Biomedicine Discovery Institute and the Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.

ABSTRACT
The yeast Candida albicans is a human commensal and opportunistic pathogen. Although both commensalism and pathogenesis depend on metabolic adaptation, the regulatory pathways that mediate metabolic processes in C. albicans are incompletely defined. For example, metabolic change is a major feature that distinguishes community growth of C. albicans in biofilms compared to suspension cultures, but how metabolic adaptation is functionally interfaced with the structural and gene regulatory changes that drive biofilm maturation remains to be fully understood. We show here that the RNA binding protein Puf3 regulates a posttranscriptional mRNA network in C. albicans that impacts on mitochondrial biogenesis, and provide the first functional data suggesting evolutionary rewiring of posttranscriptional gene regulation between the model yeast Saccharomyces cerevisiae and C. albicans. A proportion of the Puf3 mRNA network is differentially expressed in biofilms, and by using a mutant in the mRNA deadenylase CCR4 (the enzyme recruited to mRNAs by Puf3 to control transcript stability) we show that posttranscriptional regulation is important for mitochondrial regulation in biofilms. Inactivation of CCR4 or dis-regulation of mitochondrial activity led to altered biofilm structure and over-production of extracellular matrix material. The extracellular matrix is critical for antifungal resistance and immune evasion, and yet of all biofilm maturation pathways extracellular matrix biogenesis is the least understood. We propose a model in which the hypoxic biofilm environment is sensed by regulators such as Ccr4 to orchestrate metabolic adaptation, as well as the regulation of extracellular matrix production by impacting on the expression of matrix-related cell wall genes. Therefore metabolic changes in biofilms might be intimately linked to a key biofilm maturation mechanism that ultimately results in untreatable fungal disease.

No MeSH data available.


Related in: MedlinePlus