Metschnikowia pulcherrima is a highly effective biocontrol yeast due to its pigment pulcherrimin that accumulates in the cells and in the growth medium. Three different strains of M. pulcherrima were isolated from local grapes. The yeast isolates were characterized on the basis of their biochemical, physiological and ITS1-5.8 s rDNA-ITS2 region. Based on the obtained results, the M. pulcherrima isolates were identifi ed as new strains of M. pulcherrima. Strong antagonistic activities of the M. pulcherrima strains on the human pathogens Proteus vulgaris, Escherichia coli, Candida albicans, Candida parapsilosis, Candida krusei, and Trichosporon mucoides were determined. In addition, antagonistic effects of these M. pulcherrima strains were also tested against Aspergillus fl avus, Aspergillus fumigatus, Aspergillus niger, Trichoderma spp., Paecilomyces spp., and Bipolaris spp. and it was shown that the three different strains of M. pulcherrima also have an antagonistic effect on the growth of these fungal species at different extents. This study showed that all three strains of M. pulcherrima produce the same amount of the pigment pulcherrimin, but their antimicrobial activities on different microorganisms show important variations.
The strains of the yeast Metschnikowia pulcherrima have strong biocontrol activity against various microorganisms. Biocontrol activity of M. pulcherrima largely depends on its iron immobilizing pigment pulcherrimin. Biocontrol activity of pulcherrimin producing strain, M. pulcherrima UMY15, isolated from local vineyards, was tested on different molds that cause food spoilage. M. pulcherrima UMY15 was a very effective biocontrol agent against Penicillium roqueforti, P. italicum, P. expansum, and Aspergillus oryzae in in-vitro plate tests. However, the inhibitory activity of M. pulcherrima UMY15 was less effective on Fusarium sp. and A. niger species in biocontrol assays. In addition, M. pulcherrima UMY15 strain completely inhibited the germination and mycelia growth of A. oryzae, A. parasiticus, and Fusarium sp. spores on artificial wounds of apples when they coinoculated with M. pulcherrima UMY15. Moreover, when coinoculated, M. pulcherrima UMY15 strain also inhibited the growth of P. roqueforti, P. italicum, P. expansum, A. oryzae, Fusarium sp., and Rhizopus sp. in grape juice, indicating that M. pulcherrima UMY15 can be used as a very effective biocontrol yeast against various species of postharvest pathogens, including Penicillium, Aspergillus, Fusarium, and Rhizopus.
Transcription of Saccharomyces cerevisiae Ty2‐917 retrotransposon depends on regulatory elements both upstream and downstream of the transcription initiation site. An upstream activation sequence (UAS) and a downstream enhancer stimulate transcription synergistically. Here we show that activation by both of these sites depends on the GCR1 product, a transcription factor which also regulates the genes encoding yeast glycolytic enzymes. Eliminating GCR1 causes a 100‐fold decrease in transcription of Ty2‐917. Activation by the isolated Ty2‐917 UAS also strongly depends on GCR1. Unexpectedly, GCR1‐dependent activation by the Ty2‐917 enhancer is strongly position‐dependent. Activation by the enhancer in its normal position within the transcription unit depended strongly on GCR1, but eliminating GCR1 reduced activation only three‐fold when the enhancer was moved upstream of the transcribed region. Gel mobility shift and DNaseI protection assays indicated that GCR1 binds specifically to multiple sites within the Ty2‐917 UAS and enhancer regions. © 1997 John Wiley & Sons, Ltd.
includes a site recognized by the product of a gene, STE12, required for expression of haploid-specific genes, including Tyl elements (7, 12); its binding site is termed a sterile responsive element, SRE (7). Tyl and Ty2 elements include a second downstream region which represses transcription of the element (8, 15); they may be analogous to transcriptional silencers (4), since they repress transcription at a distance. The maximal level of Ty transcription presumably depends upon the interplay between positively and negatively acting transcription factors bound to the various sites.Many genes other than STE12 have been identified genetically as suppressors of Ty and 8 LTR insertions into the promoters of various genes; the genes identified are termed SPT (16,36,37). Few of these have been shown to interact directly with the element; an exception is the product of the SPT15 gene, the TATA-binding factor TFIID of S. cerevisiae (11). The products of several of the genes, SPT3, SPT7, SPT8, and SPT15, are required for normal Ty transcription (11,37,38). Many SPT gene products have a global role in regulation of transcription, as indicated by their pleiotropic phenotypic effects, including defects in sporulation and mating (36,38). Several SPT mutation genes also regulate SUC2 transcription (reference 23 and references therein); correspondingly, some SUC2 regulators (SNF and SSN genes) also alter the effect of Ty promoter insertions. The connection among these genes is underscored by genetic interactions among SPT and SNFISSN mutations. This connection could reflect alteration of chromatin structure and its effect on transcription (32). Alteration of chromatin structure is known to affect Tyl transcription. SPT11 and SPT12 encode histones H2A and H2B; mutations in these genes alter dosage of histones affecting Ty-regulated transcription (6). The SPT2ISINI, SPT4, SPT5, and SPT6ISSN6 genes may act to establish an appropriate chromatin context for regulation of transcription by gene-specific activators (32).
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