101
|
Abstract
Over 25 years ago it was noted that the pH of the culture medium influenced germ tube formation of Candida albicans, an opportunistic fungal pathogen. This simple observation has been the stimulus for a number of investigations to discern the mechanisms controlling this response and the significance of this response to the biology of C. albicans. Recent studies have demonstrated that a signaling pathway conserved in several fungal species regulates this morphological response to ambient pH and controls the pH-conditional expression of multiple genes. Significantly, C. albicans responds to the pH of the host niche and this response is critical for virulence.
Collapse
Affiliation(s)
- W A Fonzi
- Department of Microbiology and Immunology, Georgetown University, 3900 Reservoir Road NW, Washington, DC 20007, USA.
| |
Collapse
|
102
|
Meyer V, Stahl U. New insights in the regulation of the afp gene encoding the antifungal protein of Aspergillus giganteus. Curr Genet 2002; 42:36-42. [PMID: 12420144 DOI: 10.1007/s00294-002-0324-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2002] [Revised: 07/26/2002] [Accepted: 08/12/2002] [Indexed: 11/30/2022]
Abstract
The antifungal protein (AFP) secreted by the mould Aspergillus giganteus is a small, highly basic polypeptide with antifungal activity. Previous work has shown that transcription of the corresponding afp gene is regulated by ambient pH, being suppressed under acidic and strongly induced under alkaline conditions. This observation suggested that the afp gene is regulated by the wide-domain transcriptional factor PacC. Here, we show that two putative PacC binding sites within the afp promoter, denoted afpP1 and afpP2, are efficiently recognised in vitro by a PacC fusion protein of A. nidulans. In addition, we found that phosphate, which was used as a buffering agent during cultivation, plays an important role in regulating afp expression. AFP production was nearly completely inhibited in the presence of external phosphate. The results of Northern analysis indicate that the inhibitory effect of phosphate is mediated at the transcriptional level.
Collapse
Affiliation(s)
- Vera Meyer
- Technische Universität Berlin, Institut für Biotechnologie, Fachgebiet Mikrobiologie und Genetik, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
| | | |
Collapse
|
103
|
Eshel D, Miyara I, Ailing T, Dinoor A, Prusky D. pH regulates endoglucanase expression and virulence of Alternaria alternata in persimmon fruit. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2002; 15:774-779. [PMID: 12182334 DOI: 10.1094/mpmi.2002.15.8.774] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The phytopathogenic fungus Alternaria alternata produces one endo-1,4-beta-glucanase, AaK1, which is an important factor in disease development in persimmon fruit. During growth of A. alternata in media containing acidified yeast extract or cell walls from persimmon fruit, the fungus secreted ammonia and raised the medium pH. A rise in media pH from 3.8 to 6.0 in the presence of cell walls induced the expression of AaK1, whereas a glucose-induced decline in pH to 2.5 repressed transcription and enzymatic production. Treatments with buffered solutions at pH 6.0 during growth of A. alternata in the presence of glucose derepressed AaK1 expression and endo-1,4-beta-glucanase production and enhanced decay development on the fruit. The results suggest that conditions affecting environmental pH modulate gene expression of AaK1 and virulence of A. alternata in persimmon fruit
Collapse
Affiliation(s)
- Dani Eshel
- Department of Postharvest Science of Fresh Produce, Institute for Technology and Storage of Agricultural Products, The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
| | | | | | | | | |
Collapse
|
104
|
Chávez R, Schachter K, Navarro C, Peirano A, Aguirre C, Bull P, Eyzaguirre J. Differences in expression of two endoxylanase genes (xynA and xynB) from Penicillium purpurogenum. Gene 2002; 293:161-8. [PMID: 12137954 DOI: 10.1016/s0378-1119(02)00720-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A number of xylanolytic microorganisms secrete to the medium several molecular forms of endoxylanases. The physiological function of these isoforms is not clear; one possibility is that they are produced under different growth conditions. To study this problem, we have used two endoxylanases (XynA and XynB) produced by the fungus Penicillium purpurogenum. These enzymes have been previously purified and characterized; they belong to family 10 and 11 of the glycosyl hydrolases, respectively. The promoters of the xynA and xynB genes have been sequenced; both present consensus sequences for the binding of the carbon catabolite repressor CreA, but otherwise show substantial differences. The xynB promoter has eight boxes in tandem for the binding of the XlnR activator and lacks the consensus sequence for the PacC pH regulator. On the other hand, the xynA promoter contains one XlnR box and three PacC consensus sequences. To investigate if these differences are reflected in gene expression, Northern blot assays were carried out. The xynA gene is transiently expressed when oat spelt xylan is used as carbon source, but negligible expression was observed with birchwood xylan, xylose or xylitol. In contrast, xynB is broadly induced by all these carbon sources; this may be related to the presence of several XlnR boxes. Similar results were obtained by zymogram analysis of the expressed proteins. The different induction capabilities of birchwood and oat spelt xylan may be due to differences in their composition and structure. Expression assays carried out at different pH reflects that, despite the lack of PacC binding sites in the xynB promoter, this gene is tightly regulated by pH. The findings described here illustrate new and important differences between endoxylanases from families 10 and 11 in P. purpurogenum. They may help explain the production of multiple endoxylanase forms by this organism.
Collapse
MESH Headings
- Base Sequence
- Cell Division/drug effects
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- Endo-1,4-beta Xylanases
- Gene Expression Regulation, Bacterial
- Gene Expression Regulation, Enzymologic
- Glucose/pharmacology
- Hydrogen-Ion Concentration
- Isoenzymes/genetics
- Molecular Sequence Data
- Penicillium/drug effects
- Penicillium/enzymology
- Penicillium/genetics
- Promoter Regions, Genetic/genetics
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sequence Analysis, DNA
- Xylans/pharmacology
- Xylosidases/genetics
Collapse
Affiliation(s)
- Renato Chávez
- Laboratorio de Bioquímica, Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
| | | | | | | | | | | | | |
Collapse
|
105
|
MacCabe AP, Orejas M, Tamayo EN, Villanueva A, Ramón D. Improving extracellular production of food-use enzymes from Aspergillus nidulans. J Biotechnol 2002; 96:43-54. [PMID: 12142142 DOI: 10.1016/s0168-1656(02)00036-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Filamentous fungi, and particularly those of the genus Aspergillus, are major producers of enzymatic activities that have important applications in the food and beverage industries. Prior to the availability of transformation systems improvement of industrial production strains was largely restricted to the strategy of mutagenesis, screening and selection. Aspergillus nidulans is a genetically amenable filamentous fungus the ease of handling and analysis of which has led to its use as a model system for the investigation of eukaryotic gene regulation. Although not used industrially it is able to produce a wide variety of extracellular enzymatic activities. As a consequence of half a century of study a considerable resource of characterised mutants has been generated in conjunction with extensive genetic and molecular information on various gene regulatory systems in this micro-organism. Investigation of xylanase gene regulation in A. nidulans as a model for the production of food-use extracellular enzymes suggests strategies by which production of these enzymes in industrially useful species may be improved.
Collapse
Affiliation(s)
- A P MacCabe
- Instituto de Agroquímica y Tecnología de Alimentos (CSIC), Apartado de Correos 73, 46100, Valencia, Burjassot, Spain.
| | | | | | | | | |
Collapse
|
106
|
Ehrlich KC, Montalbano BG, Cary JW, Cotty PJ. Promoter elements in the aflatoxin pathway polyketide synthase gene. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1576:171-5. [PMID: 12031498 DOI: 10.1016/s0167-4781(02)00282-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PksA catalyzes the formation of the polyketide backbone necessary for aflatoxin biosynthesis. Based on reporter assays and sequence comparisons of the nor1-pksA intergenic region in different aflatoxin-producing Aspergillus species, cis-acting elements for the aflatoxin pathway-specific regulatory protein, AflR, and the global-acting regulatory proteins BrlA and PacC are involved in pksA promoter activity.
Collapse
Affiliation(s)
- Kenneth C Ehrlich
- Southern Regional Research Center, United States Department of Agriculture, P.O. Box 19687, 1100 R.E. Lee Blvd., New Orleans, LA 70179, USA.
| | | | | | | |
Collapse
|
107
|
Boucher N, Wu Y, Dumas C, Dube M, Sereno D, Breton M, Papadopoulou B. A common mechanism of stage-regulated gene expression in Leishmania mediated by a conserved 3'-untranslated region element. J Biol Chem 2002; 277:19511-20. [PMID: 11912202 DOI: 10.1074/jbc.m200500200] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Developmental regulation of mRNA levels in trypanosomatid protozoa is determined post-transcriptionally and often involves sequences located in the 3'-untranslated regions (3'-UTR) of the mRNAs. We have previously identified a developmentally regulated gene family in Leishmania encoding the amastin surface proteins and showed that stage-specific accumulation of the amastin mRNA is mediated by sequences within the 3'-UTR. Here we identified a 450-nt region within the amastin 3'-UTR that can confer amastigote-specific gene expression by a novel mechanism that increases mRNA translation without an increase in mRNA stability. Remarkably, this 450-nt 3'-UTR element is highly conserved among a large number of Leishmania mRNAs in several Leishmania species. Here we show that several of these mRNAs are differentially expressed in the intracellular amastigote stage of the parasite and that the 450-nt conserved element in their 3'-UTRs is responsible for stage-specific gene regulation. We propose that the 450-nt conserved element, which is unlike any other regulatory element identified thus far, is part of a common mechanism of stage-regulated gene expression in Leishmania that regulates mRNA translation in response to intracellular stresses.
Collapse
Affiliation(s)
- Nathalie Boucher
- Centre de Recherche en Infectiologie du Centre de Recherche du Centre Hospitalier de Université Laval, Québec G1V 4G2, Canada
| | | | | | | | | | | | | |
Collapse
|
108
|
Gonzalez-Lopez CI, Szabo R, Blanchin-Roland S, Gaillardin C. Genetic control of extracellular protease synthesis in the yeast Yarrowia lipolytica. Genetics 2002; 160:417-27. [PMID: 11861549 PMCID: PMC1461987 DOI: 10.1093/genetics/160.2.417] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Depending on the pH of the growth medium, the yeast Yarrowia lipolytica secretes an acidic protease or an alkaline protease, the synthesis of which is also controlled by carbon, nitrogen, and sulfur availability, as well as by the presence of extracellular proteins. Previous results have indicated that the alkaline protease response to pH was dependent on YlRim101p, YlRim8p/YlPalF, and YlRim21p/YlPalH, three components of a conserved pH signaling pathway initially described in Aspergillus nidulans. To identify other partners of this response pathway, as well as pH-independent regulators of proteases, we searched for mutants that affect the expression of either or both acidic and alkaline proteases, using a YlmTn1-transposed genomic library. Four mutations affected only alkaline protease expression and identified the homolog of Saccharomyces cerevisiae SIN3. Eighty-nine mutations affected the expression of both proteases and identified 10 genes. Five of them define a conserved Rim pathway, which acts, as in other ascomycetes, by activating alkaline genes and repressing acidic genes at alkaline pH. Our results further suggest that in Y. lipolytica this pathway is active at acidic pH and is required for the expression of the acidic AXP1 gene. The five other genes are homologous to S. cerevisiae OPT1, SSY5, VPS28, NUP85, and MED4. YlOPT1 and YlSSY5 are not involved in pH sensing but define at least a second protease regulatory pathway.
Collapse
Affiliation(s)
- Claudia I Gonzalez-Lopez
- Laboratoire de Génétique Moléculaire et Cellulaire, Institut National Agronomique Paris-Grignon, Centre National de la Recherche Scientifique URA1925, 78850 Thiverval-Grignon, France
| | | | | | | |
Collapse
|
109
|
de Vries RP, Visser J. Aspergillus enzymes involved in degradation of plant cell wall polysaccharides. Microbiol Mol Biol Rev 2001; 65:497-522, table of contents. [PMID: 11729262 PMCID: PMC99039 DOI: 10.1128/mmbr.65.4.497-522.2001] [Citation(s) in RCA: 542] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Degradation of plant cell wall polysaccharides is of major importance in the food and feed, beverage, textile, and paper and pulp industries, as well as in several other industrial production processes. Enzymatic degradation of these polymers has received attention for many years and is becoming a more and more attractive alternative to chemical and mechanical processes. Over the past 15 years, much progress has been made in elucidating the structural characteristics of these polysaccharides and in characterizing the enzymes involved in their degradation and the genes of biotechnologically relevant microorganisms encoding these enzymes. The members of the fungal genus Aspergillus are commonly used for the production of polysaccharide-degrading enzymes. This genus produces a wide spectrum of cell wall-degrading enzymes, allowing not only complete degradation of the polysaccharides but also tailored modifications by using specific enzymes purified from these fungi. This review summarizes our current knowledge of the cell wall polysaccharide-degrading enzymes from aspergilli and the genes by which they are encoded.
Collapse
Affiliation(s)
- R P de Vries
- Molecular Genetics of Industrial Microorganisms, Wageningen University, 6703 HA Wageningen, The Netherlands.
| | | |
Collapse
|
110
|
Prusky D, McEvoy JL, Leverentz B, Conway WS. Local modulation of host pH by Colletotrichum species as a mechanism to increase virulence. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2001; 14:1105-1113. [PMID: 11551075 DOI: 10.1094/mpmi.2001.14.9.1105] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The phytopathogenic fungus Colletotrichum gloeosporioides produces one pectate lyase (PL) that is a key virulence factor in disease development. During growth of C. gloeosporioides, Colletotrichum acutatum, and Colletotrichum coccodes in acidified yeast extract medium, the fungus secreted ammonia and increased the medium pH. Ammonia accumulation and the consequent pH change increased as a function of initial pH and buffer capacity of the medium. PL secretion by C. gloeosporioides correspondingly increased as the pH of the medium increased. The C. gloeosporioides pelB gene-disrupted mutant was able to increase ammonia accumulation and pH of the media similarly to the wild-type isolate. C. gloeosporioides in avocado, C. coccodes in tomato, and C. acutatum in apple showed ammonia accumulation in the infected area where pH increased to 7.5 to 8 and PL activity is optima. In nonhost interactions where C. gloeosporioides was inoculated in apples, the addition of ammonia-releasing compounds significantly enhanced pathogenicity to levels similar to those caused by the compatible C. acutatum-apple interaction. The results therefore suggest the importance of ammonia secretion as a virulence factor, enhancing environmental pH and pathogenicity of the Colletotrichum species.
Collapse
Affiliation(s)
- D Prusky
- Henry A. Wallace Beltsville Agricultural Research Center, Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705, USA.
| | | | | | | |
Collapse
|
111
|
Current Awareness on Comparative and Functional Genomics. Comp Funct Genomics 2001. [PMCID: PMC2447185 DOI: 10.1002/cfg.55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
112
|
Navarro-García F, Eisman B, Román E, Nombela C, Pla J. Signal transduction pathways and cell-wall construction inCandida albicans. Med Mycol 2001. [DOI: 10.1080/mmy.39.1.87.100] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
|