Effects of genome duplication on phenotypes and industrial applications of Saccharomyces cerevisiae strains.

Polyploidy is common in Saccharomyces cerevisiae strains, but the physiological and phenotypic effects of ploidy changes have not been fully clarified. Here, isogenic diploid, triploid, and tetraploid S. cerevisiae strains were constructed from a haploid strain, CEN.PK2-1C. Stress tolerance and ethanol fermentation performance of the four euploid strains were compared. Each euploid strain had strengths and weaknesses in tolerance to certain stressors, and no single strain was tolerant of all stressors. The diploid had higher ethanol production than the other strains in normal fermentation medium, while the triploid strain showed the fastest fermentation rate in the presence of inhibitors found in lignocellulosic hydrolysate. Physiological determination revealed diverse physiological attributes, such as trehalose, ergosterol, glutathione, and anti-oxidative enzymes among the strains. Our analyses suggest that both ploidy parity and number of chromosome sets contribute to changes in physiological status. Using qRT-PCR, different expression patterns of genes involved in the regulation of cell morphology and the biosynthesis of key physiological attributes among strains were determined. Our data provide novel insights into the multiple effects of genome duplication on yeast cells and are a useful reference for breeding excellent strains used in specific industrial applications.

Genomic structural variations contribute to trait improvement during whole-genome shuffling of yeast.

Whole-genome shuffling (WGS) is a powerful technology of improving the complex traits of many microorganisms. However, the molecular mechanisms underlying the altered phenotypes in isolates were less clarified. Isolates with significantly enhanced stress tolerance and ethanol titer under very-high-gravity conditions were obtained after WGS of the bioethanol Saccharomyces cerevisiae strain ZTW1. Karyotype analysis and RT-qPCR showed that chromosomal rearrangement occurred frequently in genome shuffling. Thus, the phenotypic effects of genomic structural variations were determined in this study. RNA-Seq and physiological analyses revealed the diverse transcription pattern and physiological status of the isolate S3-110 and ZTW1. Our observations suggest that the improved stress tolerance of S3-110 can be largely attributed to the copy number variations in large DNA regions, which would adjust the ploidy of yeast cells and expression levels of certain genes involved in stress response. Overall, this work not only constructed shuffled S. cerevisiae strains that have potential industrial applications but also provided novel insights into the molecular mechanisms of WGS and enhanced our knowledge on this useful breeding strategy.

[Effects of sulfur starvation on the non-protein thiol content and glutathione S-transferase activity of rice seedlings under cadmium stress].

By installing a treatment of sulfur starvation, this paper studied the dynamic changes of rice seedling growth, cadmium (Cd) and non-protein thiol (NPT) contents, and glutathione S-transferase (GST) activity under Cd stress. Cd stress inhibited the seedling growth obviously, induced the synthesis of sulfhydryl (-SH) compounds, including non-protein thiol, glutathione, and phytochelatins, and made the GST activity decreased after an initial increase. Sulfur starvation somewhat increased the Cd uptake and translocation, but less affected the impacts of Cd stress. The contents of -SH compounds decreased, and the GST activity in root increased. It was suggested that the roles of -SH compounds and GST in Cd-resistance of rice were complementary, being able to alleviate the Cd toxicity to some extent.