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C Clavé

Publications and source records attributed to C Clavé.

11 recordsLinked to original sources
PubMed2001

Identification and characterization of a gene encoding a subtilisin-like serine protease induced during the vegetative incompatibility reaction in Podospora anserina.

In the filamentous fungi, cell fusion between unlike individuals generally triggers a cell-death reaction known as vegetative incompatibility. In Podospora anserina, it was shown that, during this cell-death reaction, there is a strong increase in proteolytic activity. Here, we report the purification of a 36-kDa protease that is induced during the incompatibility reaction. An internal peptide of this protein displayed a strong similarity with the PEPC subtilisin-like serine protease from Aspergillus niger. This led us to use the pepC gene as a probe to clone the homologous gene from P. anserina, which we called pspA. The expression of pspA is upregulated at the transcript level during the progress of the incompatibility reaction. This induction is diminished in strains bearing suppressors of the vegetative incompatibility reaction. The fact that pspA is homologous to PrB, a vacuolar protease involved in autophagy in yeast, suggests that the incompatibility cell-death reaction and autophagy might be related processes.

Amino Acid Sequence↗
PubMed2000

Characterization of hch, the Podospora anserina homolog of the het-c heterokaryon incompatibility gene of Neurospora crassa.

The het-c locus controls heterokaryon formation in Neurospora crassa. It is subject to balancing selection operating to maintain polymorphism at that locus in natural populations. We have isolated hch, the het-c homolog from the related species Podospora anserina (hch for het-c homolog), in order to determine if this gene also functions as a het gene in that species. The het-c and hch sequences are highly similar but differ in the region defining allele specificity in N. crassa het-c. Analysis of hch variability in 11 natural P. anserina isolates with different het genotypes revealed no polymorphism. This suggested that hch does not function as a het gene. However, heterologous expression of the N. crassa het-cPA allele in P. anserina triggers a growth defect reminiscent of the het-c incompatibility reaction.

Amino Acid Sequence↗
PubMed2000

Vegetative incompatibility in filamentous fungi: Podospora and Neurospora provide some clues.

In filamentous fungi, vegetative cell fusion between genotypically distinct individuals leads to a cell-death reaction known as vegetative or heterokaryon incompatibility. Genes involved in this reaction have been characterised molecularly. We can now begin to get a better understanding of the mechanism and the biological significance of this intriguing phenomenon.

Amino Acid Sequence↗
PubMed1998

Characterization of a gene from the filamentous fungus Podospora anserina encoding an aspartyl protease induced upon carbon starvation.

In an attempt to characterize proteases associated with vegetative incompatibility, a Podospora anserina gene (papA) encoding an aspartyl protease (podosporapepsin) was cloned using a heterologous probe. The deduced papA coding region was 1278 nucleotides long, interrupted by a single 71bp intron. The corresponding amino acid sequence presented a high degree of similarity to other aspartyl proteases. Sequence analysis and proteolytic activity measurement suggested that the podosporapepsin could be intracellular rather than secreted. The papA gene was expressed under carbon starvation, but not under nitrogen starvation conditions. Its disruption led to a slight decrease in the growth rate of the mutant strain when bovine serum albumin was the sole carbon source in the medium. Disruption or overexpression of papA gene had no obvious consequence on vegetative incompatibility. Transcription of papA induced by carbon starvation was strongly reduced in the presence of a suppressor of vegetative incompatibility. This result suggests a relationship between adaptation for starvation and vegetative incompatibility.

Amino Acid Sequence↗
PubMed1998

Regulation of gene expression during the vegetative incompatibility reaction in Podospora anserina. Characterization of three induced genes.

Vegetative incompatibility in fungi limits the formation of viable heterokaryons. It results from the coexpression of incompatible genes in the heterokaryotic cells and leads to a cell death reaction. In Podospora anserina, a modification of gene expression takes place during this reaction, including a strong decrease of total RNA synthesis and the appearance of a new set of proteins. Using in vitro translation of mRNA and separation of protein products by two-dimensional gel electrophoresis, we have shown that the mRNA content of cells is qualitatively modified during the progress of the incompatibility reaction. Thus, gene expression during vegetative incompatibility is regulated, at least in part, by variation of the mRNA content of specific genes. A subtractive cDNA library enriched in sequences preferentially expressed during incompatibility was constructed. This library was used to identify genomic loci corresponding to genes whose mRNA is induced during incompatibility. Three such genes were characterized and named idi genes for genes induced during incompatibility. Their expression profiles suggest that they may be involved in different steps of the incompatibility reaction. The putative IDI proteins encoded by these genes are small proteins with signal peptides. IDI-2 protein is a cysteine-rich protein. IDI-2 and IDI-3 proteins display some similarity in a tryptophan-rich region.

Amino Acid Sequence↗
PubMed1994

Vegetative incompatibility in filamentous fungi: het genes begin to talk.

Somatic or vegetative incompatibility is widespread in filamentous fungi. It prevents the coexistence of genetically different nuclei within a common cytoplasm. Cloning the het genes that control this process has been achieved in several species. This has provided essential information on the function of the genes in the biology of fungi and has also led to the formulation of models that may explain similar phenomena in other organisms.

Cloning, Molecular↗
PubMed1993

A single amino acid difference is sufficient to elicit vegetative incompatibility in the fungus Podospora anserina.

Vegetative incompatibility is known to limit heterokaryosis in filamentous fungi. It results from genetic differences between incompatible strains at specific loci. The proteins encoded by the two incompatible alleles het-s and het-S of the fungus Podospora anserina differ from each other by 14 amino acids. Two approaches have been used to identify how many and which of these differences are necessary to elicit incompatibility. Twelve alleles of the het-s locus of wild-type isolates of P. anserina and of the related species Podospora comata have been sequenced to determine the extent of the variability of genes controlling s and S specificities. Expression of hybrid het-s/het-S genes and site-specific mutagenesis revealed that the specificities of het-s and het-S are under the control of a limited number of amino acid differences. The results show that vegetative incompatibility between s and S strains can be attributed to a single amino acid difference in the proteins encoded by the het-s locus.

Alleles↗
PubMed1992

Calcium regulation of growth and differentiation in Streptococcus pneumoniae.

Streptococcus pneumoniae requires 0.15 mM-Ca2+ in the medium for optimal growth. Increasing the Ca2+ concentration to 1 mM triggers either a differentiative state, competence for genetic transformation during exponential growth, or partial lysis as soon as the cultures enter stationary phase. Genetic and physiological data both suggest that these responses are under the control of activator(s), excreted in the presence of high Ca2+ concentrations. 45Ca2+ transport is also stimulated by the activator(s). The amiloride derivative 2',4'-dimethylbenzamil (DMB) inhibits 45Ca2+ transport and prevents lysis and competence development. This provides evidence in favour of the involvement of Ca2+ transport in competence and culture lysis. On the other hand, addition of DNA to a competent culture prevents lysis of wild-type bacteria while a mutant, defective for DNA uptake, is not protected from lysis by exogenous DNA. An hypothesis is proposed for competence induction as a global metabolic response to Ca2+, under the control of competence factor.

Amiloride↗
PubMed1989

DNA uptake in competent Streptococcus pneumoniae requires ATP and is regulated by cytoplasmic pH.

DNA uptake in competent Streptococcus pneumoniae was strongly dependent on intracellular pH. Ionophore treatments that either acidified or alkalinized the cytoplasm reduced DNA transport. This indicates that the optimum pH for DNA uptake corresponds to the intracellular pH of competent bacteria which is 8.3 +/- 0.2. In addition, the ATP pool of the bacteria appeared to be a critical parameter in the process. The pattern of inhibition by arsenate, when the culture was treated at different steps of the competence cycle, suggested firstly, that a threshold ATP level was required to trigger transport and secondly, an ATP requirement for the process itself. This may indicate an ATP involvement in the activation of an uptake machinery functioning at the expense of ATP.

Adenosine Triphosphate↗
PubMed1989

Ionic and energetic changes at competence in the naturally transformable bacterium Streptococcus pneumoniae.

Addition of competence factor extracts to trigger competence in a culture of Streptococcus pneumoniae induced an increase in the intracellular pH and the Na+ content of the bacteria without any change in the K+ pool or in the membrane potential. These ionic shifts were concomitant with a stimulation of glycolysis that resulted in an enhanced ATP pool. Thus, in transforming conditions, at extracellular pH 7.8, competent bacteria presented a particularly high energetic state resulting from an increase in delta pH and in the ATP pool, associated with an enhanced Na+ content. These features are discussed in the context of homeostasis regulation in response to an environmental stimulus.

Adenosine Triphosphate↗