Gene_locus Report for: yeast-LDH1

Autophagy is a major catabolic process responsible for the delivery of proteins and organelles to the lysosome/vacuole for degradation. Malfunction of this pathway has been implicated in numerous pathological conditions. Different organelles have been found to contribute to the formation of autophagosomes, but the exact mechanism mediating this process remains obscure. Here, we show that lipid droplets (LDs) are important for the regulation of starvation-induced autophagy. Deletion of Dga1 and Lro1 enzymes responsible for triacylglycerol (TAG) synthesis, or of Are1 and Are2 enzymes responsible for the synthesis of steryl esters (STE), results in the inhibition of autophagy. Moreover, we identified the STE hydrolase Yeh1 and the TAG lipase Ayr1 as well as the lipase/hydrolase Ldh1 as essential for autophagy. Finally, we provide evidence that the ER-LD contact-site proteins Ice2 and Ldb16 regulate autophagy. Our study thus highlights the importance of lipid droplet dynamics for the autophagic process under nitrogen starvation.

Here, we report the functional characterization of the newly identified lipid droplet hydrolase Ldh1p. Recombinant Ldh1p exhibits esterase and triacylglycerol lipase activities. Mutation of the serine in the hydrolase/lipase motif GXSXG completely abolished esterase activity. Ldh1p is required for the maintenance of a steady-state level of the nonpolar and polar lipids of lipid droplets. A characteristic feature of the Saccharomyces cerevisiae Deltaldh1 strain is the appearance of giant lipid droplets and an excessive accumulation of nonpolar lipids and phospholipids upon growth on medium containing oleic acid as a sole carbon source. Ldh1p is thought to play a role in maintaining the lipid homeostasis in yeast by regulating both phospholipid and nonpolar lipid levels.

Here, we report the identification of a novel hydrolase in Saccharomyces cerevisiae. Ldh1p (systematic name, Ybr204cp) comprises the typical GXSXG-type lipase motif of members of the alpha/beta-hydrolase family and shares some features with the peroxisomal lipase Lpx1p. Both proteins carry a putative peroxisomal targeting signal type1 (PTS1) and can be aligned with two regions of homology. While Lpx1p is known as a peroxisomal enzyme, subcellular localization studies revealed that Ldh1p is predominantly localized to lipid droplets, the storage compartment of nonpolar lipids. Ldh1p is not required for the function and biogenesis of peroxisomes, and targeting of Ldh1p to lipid droplets occurs independently of the PTS1 receptor Pex5p.

Autophagy is a major catabolic process responsible for the delivery of proteins and organelles to the lysosome/vacuole for degradation. Malfunction of this pathway has been implicated in numerous pathological conditions. Different organelles have been found to contribute to the formation of autophagosomes, but the exact mechanism mediating this process remains obscure. Here, we show that lipid droplets (LDs) are important for the regulation of starvation-induced autophagy. Deletion of Dga1 and Lro1 enzymes responsible for triacylglycerol (TAG) synthesis, or of Are1 and Are2 enzymes responsible for the synthesis of steryl esters (STE), results in the inhibition of autophagy. Moreover, we identified the STE hydrolase Yeh1 and the TAG lipase Ayr1 as well as the lipase/hydrolase Ldh1 as essential for autophagy. Finally, we provide evidence that the ER-LD contact-site proteins Ice2 and Ldb16 regulate autophagy. Our study thus highlights the importance of lipid droplet dynamics for the autophagic process under nitrogen starvation.

Here, we report the functional characterization of the newly identified lipid droplet hydrolase Ldh1p. Recombinant Ldh1p exhibits esterase and triacylglycerol lipase activities. Mutation of the serine in the hydrolase/lipase motif GXSXG completely abolished esterase activity. Ldh1p is required for the maintenance of a steady-state level of the nonpolar and polar lipids of lipid droplets. A characteristic feature of the Saccharomyces cerevisiae Deltaldh1 strain is the appearance of giant lipid droplets and an excessive accumulation of nonpolar lipids and phospholipids upon growth on medium containing oleic acid as a sole carbon source. Ldh1p is thought to play a role in maintaining the lipid homeostasis in yeast by regulating both phospholipid and nonpolar lipid levels.

Here, we report the identification of a novel hydrolase in Saccharomyces cerevisiae. Ldh1p (systematic name, Ybr204cp) comprises the typical GXSXG-type lipase motif of members of the alpha/beta-hydrolase family and shares some features with the peroxisomal lipase Lpx1p. Both proteins carry a putative peroxisomal targeting signal type1 (PTS1) and can be aligned with two regions of homology. While Lpx1p is known as a peroxisomal enzyme, subcellular localization studies revealed that Ldh1p is predominantly localized to lipid droplets, the storage compartment of nonpolar lipids. Ldh1p is not required for the function and biogenesis of peroxisomes, and targeting of Ldh1p to lipid droplets occurs independently of the PTS1 receptor Pex5p.

Bioethanol is a biofuel produced mainly from the fermentation of carbohydrates derived from agricultural feedstocks by the yeast Saccharomyces cerevisiae. One of the most widely adopted strains is PE-2, a heterothallic diploid naturally adapted to the sugar cane fermentation process used in Brazil. Here we report the molecular genetic analysis of a PE-2 derived diploid (JAY270), and the complete genome sequence of a haploid derivative (JAY291). The JAY270 genome is highly heterozygous (approximately 2 SNPs/kb) and has several structural polymorphisms between homologous chromosomes. These chromosomal rearrangements are confined to the peripheral regions of the chromosomes, with breakpoints within repetitive DNA sequences. Despite its complex karyotype, this diploid, when sporulated, had a high frequency of viable spores. Hybrid diploids formed by outcrossing with the laboratory strain S288c also displayed good spore viability. Thus, the rearrangements that exist near the ends of chromosomes do not impair meiosis, as they do not span regions that contain essential genes. This observation is consistent with a model in which the peripheral regions of chromosomes represent plastic domains of the genome that are free to recombine ectopically and experiment with alternative structures. We also explored features of the JAY270 and JAY291 genomes that help explain their high adaptation to industrial environments, exhibiting desirable phenotypes such as high ethanol and cell mass production and high temperature and oxidative stress tolerance. The genomic manipulation of such strains could enable the creation of a new generation of industrial organisms, ideally suited for use as delivery vehicles for future bioenergy technologies.

Many industrial strains of Saccharomyces cerevisiae have been selected primarily for their ability to convert sugars into ethanol efficiently despite exposure to a variety of stresses. To begin investigation of the genetic basis of phenotypic variation in industrial strains of S. cerevisiae, we have sequenced the genome of a wine yeast, AWRI1631, and have compared this sequence with both the laboratory strain S288c and the human pathogenic isolate YJM789. AWRI1631 was found to be substantially different from S288c and YJM789, especially at the level of single-nucleotide polymorphisms, which were present, on average, every 150 bp between all three strains. In addition, there were major differences in the arrangement and number of Ty elements between the strains, as well as several regions of DNA that were specific to AWRI1631 and that were predicted to encode proteins that are unique to this industrial strain.

We sequenced the genome of Saccharomyces cerevisiae strain YJM789, which was derived from a yeast isolated from the lung of an AIDS patient with pneumonia. The strain is used for studies of fungal infections and quantitative genetics because of its extensive phenotypic differences to the laboratory reference strain, including growth at high temperature and deadly virulence in mouse models. Here we show that the approximately 12-Mb genome of YJM789 contains approximately 60,000 SNPs and approximately 6,000 indels with respect to the reference S288c genome, leading to protein polymorphisms with a few known cases of phenotypic changes. Several ORFs are found to be unique to YJM789, some of which might have been acquired through horizontal transfer. Localized regions of high polymorphism density are scattered over the genome, in some cases spanning multiple ORFs and in others concentrated within single genes. The sequence of YJM789 contains clues to pathogenicity and spurs the development of more powerful approaches to dissecting the genetic basis of complex hereditary traits.

In the framework of the EU genome-sequencing programmes, the complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome II (807 188 bp) has been determined. At present, this is the largest eukaryotic chromosome entirely sequenced. A total of 410 open reading frames (ORFs) were identified, covering 72% of the sequence. Similarity searches revealed that 124 ORFs (30%) correspond to genes of known function, 51 ORFs (12.5%) appear to be homologues of genes whose functions are known, 52 others (12.5%) have homologues the functions of which are not well defined and another 33 of the novel putative genes (8%) exhibit a degree of similarity which is insufficient to confidently assign function. Of the genes on chromosome II, 37-45% are thus of unpredicted function. Among the novel putative genes, we found several that are related to genes that perform differentiated functions in multicellular organisms of are involved in malignancy. In addition to a compact arrangement of potential protein coding sequences, the analysis of this chromosome confirmed general chromosome patterns but also revealed particular novel features of chromosomal organization. Alternating regional variations in average base composition correlate with variations in local gene density along chromosome II, as observed in chromosomes XI and III. We propose that functional ARS elements are preferably located in the AT-rich regions that have a spacing of approximately 110 kb. Similarly, the 13 tRNA genes and the three Ty elements of chromosome II are found in AT-rich regions. In chromosome II, the distribution of coding sequences between the two strands is biased, with a ratio of 1.3:1. An interesting aspect regarding the evolution of the eukaryotic genome is the finding that chromosome II has a high degree of internal genetic redundancy, amounting to 16% of the coding capacity.