Inactivation of six genes from chromosomes VII and XIV of Saccharomyces cerevisiae and basic phenotypic analysis of the mutant strains

Within the frame of the EUROFAN project, aimed at the functional analysis of the novel ORFs revealed by the systematic sequencing of the Saccharomyces cerevisiae genome, we have inactivated six ORFs encoding putative proteins with unknown function in the two S. cerevisiae strains FY1679 and W303-1B. Five ORFs are located on chromosome VII (YGR250c, YGR251w, YGR260w, YGR262c, YGR263c) and one on chromosome XIV (YNL234w). The genes have been inactivated in the FY1679 strain by a strategy that makes use of deletion cassettes containing the kanMX4 module, which confers resistance to geneticin to yeast cells, and short flanking regions homologous to the target locus (SFH). Tetrad dissection of heterozygous mutants and basic phenotypic analysis of the spores revealed that ORF YGR251w is an essential gene, while the disruption of YGR262c causes a severe slow-growth phenotype. Deletion of the remaining ORFs did not give rise to a detectable phenotype in the mutant strains. For each ORF we have cloned, in the pUG7 plasmid, a replacement cassette that possesses long flanking regions homologous to the target locus (LFH) and, in the pRS416 plasmid, the cognate wild-type gene. The LFH replacement cassettes were used to inactivate the respective genes in the W303-1B strain. This work has been performed in the framework of the B0 Consortium of the EUROFAN I project.

A novel E-type endo-beta-1,4-glucanase with a putative cellulose-binding domain is highly expressed in ripening strawberry fruits

Two full-length cDNA clones (faEG1 and faEG3, respectively) have been isolated by screening a cDNA library representing transcripts from red strawberry fruits. Southern blot analysis of genomic DNA suggests that the strawberry endo-beta-1,4-glucanases (EGases) are encoded by a multigene family. The cognate genes are predominantly expressed during the ripening process proper, although, in the case of faEG3, some expression has also been observed in large green fruits and, at low amounts, in young vegetative green tissues. In agreement with other ripening-related genes in strawberry, also the expression of faEG1 and faEG3 is down-regulated by treatment with an auxin analogue (1-naphthaleneacetic acid, NAA). Differences in temporal expression of the two EGase genes in fruits are not accompanied by differences in spatial expression. The pattern of expression and the sequence characteristics of the two polypeptides suggest that the two strawberry EGases operate in a synergistic and coordinate manner. The protein encoded by faEG1 looks like one of the usual higher-plant EGases (average molecular mass of 54 kDa), while the protein encoded by faEG3 has a greater deduced molecular mass (about 68 kDa) due to the presence of an extra peptide of about 130 amino acids at the C-terminus. Such unusual peptide shows some features also found in microbial cellulases and contains a putative cellulose-binding domain. We propose that the faEG3-encoded EGase might especially hydrolyse the xyloglucans coating the cellulose microfibrils, thus rendering the cell wall more susceptible to the subsequent hydrolytic activity of the faEG1-encoded EGase.

Analysis of a 17.9 kb region from Saccharomyces cerevisiae chromosome VII reveals the presence of eight open reading frames, including BRF1 (TFIIIB70) and GCN5 genes

We report the nucleotide sequence of a 17,893 bp DNA segment from the right arm of Saccharomyces cerevisiae chromosome VII. This fragment begins at 482 kb from the centromere. The sequence includes the BRF1 gene, encoding TFIIIB70, the 5' portion of the GCN5 gene, an open reading frame (ORF) previously identified as ORF MGA1, whose translation product shows similarity to heat-shock transcription factors and five new ORFs. Among these, YGR250 encodes a polypeptide that harbours a domain present in several polyA binding proteins. YGR245 is similar to a putative Schizosaccharomyces pombe gene, YGR248 shows significant similarity with three ORFs of S. cerevisiae situated on different chromosomes, while the remaining two ORFs, YGR247 and YGR251, do not show significant similarity to sequences present in databases.