Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2004 Jun;3(3):776-84.
doi: 10.1128/EC.3.3.776-784.2004.

RBR1, a novel pH-regulated cell wall gene of Candida albicans, is repressed by RIM101 and activated by NRG1

Henrike Lotz  1 , Kai Sohn, Herwig Brunner, Fritz A Muhlschlegel, Steffen Rupp
Affiliations

RBR1, a novel pH-regulated cell wall gene of Candida albicans, is repressed by RIM101 and activated by NRG1

Henrike Lotz et al. Eukaryot Cell. 2004 Jun.

Abstract

The transcription factor Rim101p of Candida albicans has been shown to play a major role in pH-dependent gene regulation. Rim101p is involved in cell wall biosynthesis, since it regulates PHR1 and PHR2, two almost functionally redundant cell wall glycosidases important for adaptation to either neutral or acidic habitats within the human host. To identify additional cell wall components regulated by Rim101p, we performed transcriptional profiling with a cell wall-specific DNA microarray. We showed that Rim101p contributes to the activation of known hypha-specific genes such as HWP1 and RBT1 but is also required for repression of the previously uncharacterized potential cell wall genes RBR1, RBR2, and RBR3. Further characterization of RBR1 revealed that it encodes a small glycosylphosphatidyl inositol protein that is expressed under acidic conditions predominantly at low temperature. Deletion of the gene resulted in a filamentation defect at low pH. Most interestingly, NRG1, a transcriptional repressor of hyphal growth in C. albicans, was required for RBR1 expression. The apparently activating effect of NRG1 observed in this study has not been described before. In addition, we showed that expression of NRG1 is not only temperature but also pH dependent.

PubMed Disclaimer

Figures

FIG. 1.
FIG. 1.
Rim101p activates and represses cell wall genes of C. albicans. (a) Activation of hyphal genes by RIM101. (b) Repression of RBR1, RBR2, and RBR3 by RIM101. RNA for Northern blotting was prepared from the wild-type strain SC5314 and the RIM101-1426 and rim101Δ mutants grown for 6 h in YPD with 100 mM HEPES at 30°C. Media were adjusted to pH 7.4 for SC5314 and the rim101Δ mutant (dark bars) or to pH 4.5 for SC5314 and the RIM101-1426 mutant (light bars). Quantification of mRNA abundance was done by normalizing hybridization signals to the ACT1 signal of SC5314 at pH 7.4.
FIG. 2.
FIG. 2.
pH-dependent filamentation defect of rbr1Δ mutants on M-199 soft agar. The independent rbr1Δ mutants HL12-2 and HL14-1 are shown in the lower panels; HL13-6 is derived from HL12-2. Strains were precultured in SC-uri for 24 h and pelleted by brief centrifugation. Then 5 μl of concentrated cell suspension was spotted onto the agar surface. Plates were incubated for 72 h at 30°C.
FIG. 3.
FIG. 3.
(a) RBR1 expression is activated by NRG1. Transcript levels of RBR1, PHR2, and HWP1 in the wild type (wt) and efg1Δ, nrg1Δ, and tup1Δ mutant strains were determined by Northern blotting. RNA derived from strains grown in α-MEM at pH 4.5 (lanes 1 to 4) and pH 7.4 (lanes 5 to 8) for 4 h under noninducing and hypha-inducing temperatures of 25 and 37°C, respectively. (b) Reversion of the nrg1Δ mutant strain with pMET3-NRG1 restores RBR1 expression. The wild type and nrg1Δ, and nrg1-pMET3-NRG1 mutants were grown for 4 h in α-MEM at pH 4.5 without cysteine and without methionine. rRNA*, ethidium bromide-stained loading control.
FIG. 4.
FIG. 4.
(a) Expression of NRG1 and RBR1 is RIM101 and temperature dependent. (b) pH-dependent repression of NRG1 correlates to Rim101p-dependent expression levels of HWP1. Wild-type SC5314 and RIM101-1426, and rim101Δ mutants were grown for 6 h in α-MEM with 100 mM HEPES buffered to pH 4.5 and 7.4 at 25 and 37°C to isolate RNA for Northern blot analysis. rRNA*, ethidium bromide-stained loading control.
FIG. 5.
FIG. 5.
Expression of HWP1 and RBT1 is activated by RIM101 and correlated to the RIM101-1426 overexpression phenotype. (a) RIM101-dependent expression of HWP1 and RBT1 in wild-type SC5314 and the RIM101-1426 and rim101Δ mutants was determined by Northern blotting. RNA was derived from cells grown in M-199 with 100 mM HEPES at pH 4.0 and 8.0 for 4 h. The pH and temperature values are indicated. rRNA*, ethidium bromide-stained loading control. (b) Phenotypes of the strains grown for Northern blot analysis after 4 h in M-199 at 37°C and pH 4.0 (upper panel) or pH 8.0 (lower panel).
FIG. 6.
FIG. 6.
Model of Rim101p cross talk with the NRG1 pathway. Integration of external pH signals into other signaling pathways is mediated by RIM101-dependent repression of Nrg1p. The presence of active Rim101p at neutral pH has three consequences: first, direct activation of pH-specific cell wall genes (PHR1, PRA1), second, direct or indirect repression of acid-expressed cell wall genes (PHR2, RBR1) and third, enhanced expression of hypha-specific genes by repression of NRG1. C. albicans is thus able to integrate pH signals via Rim101p and Nrg1p with other signaling pathways required, e.g., for morphogenesis to react specifically to changes in environmental conditions.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Bailey, D. A., P. J. Feldmann, M. Bovey, N. A. Gow, and A. J. Brown. 1996. The Candida albicans HYR1 gene, which is activated in response to hyphal development, belongs to a gene family encoding yeast cell wall proteins. J. Bacteriol. 178:5353-5360. - PMC - PubMed
    1. Braun, B. R., W. S. Head, M. X. Wang, and A. D. Johnson. 2000. Identification and characterization of TUP1-regulated genes in Candida albicans. Genetics 156:31-44. - PMC - PubMed
    1. Braun, B. R., and A. D. Johnson. 1997. Control of filament formation in Candida albicans by the transcriptional repressor TUP1. Science 277:105-109. - PubMed
    1. Braun, B. R., and A. D. Johnson. 2000. TUP1, CPH1 and EFG1 make independent contributions to filamentation in Candida albicans. Genetics 155:57-67. - PMC - PubMed
    1. Braun, B. R., D. Kadosh, and A. D. Johnson. 2001. NRG1, a repressor of filamentous growth in C. albicans, is down-regulated during filament induction. EMBO J. 20:4753-4761. - PMC - PubMed

Publication types

MeSH terms

LinkOut - more resources