AUTHOR=Wang Xinning , Liang Zhenzhen , Hou Jin , Shen Yu , Bao Xiaoming 

TITLE=The Absence of the Transcription Factor Yrr1p, Identified from Comparative Genome Profiling, Increased Vanillin Tolerance Due to Enhancements of ABC Transporters Expressing, rRNA Processing and Ribosome Biogenesis in Saccharomyces cerevisiae

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00367

DOI=10.3389/fmicb.2017.00367

ISSN=1664-302X

ABSTRACT=<p>Enhancing the tolerance of <italic>Saccharomyces cerevisiae</italic> to inhibitors derived from lignocellulose is conducive to producing biofuel and chemicals using abundant lignocellulosic materials. Vanillin is a major type of phenolic inhibitor in lignocellulose hydrolysates for <italic>S. cerevisiae</italic>. In the present work, the factors beneficial to vanillin resistance in yeast were identified from the vanillin-resistant strain EMV-8, which was derived from strain NAN-27 by adaptive evolution. We found 450 SNPs and 44 genes with InDels in the vanillin-tolerant strain EMV-8 by comparing the genome sequences of EMV-8 and NAN-27. To investigate the effects of InDels, InDels were deleted in BY4741, respectively. We demonstrated that the deletion of <italic>YRR1</italic> improved vanillin tolerance of strain. In the presence of 6 mM vanillin, deleting <italic>YRR1</italic> increase the maximum specific growth rate and the vanillin consumption rate by 142 and 51%, respectively. The subsequent transcriptome analysis revealed that deleting <italic>YRR1</italic> resulted in changed expression of over 200 genes in the presence of 5 mM vanillin. The most marked changes were the significant up-regulation of the dehydrogenase <italic>ADH7</italic>, several ATP-binding cassette (ABC) transporters, and dozens of genes involved in ribosome biogenesis and rRNA processing. Coincidently, the crude enzyme solution of BY4741(<italic>yrr1</italic>Δ) exhibited higher NADPH-dependent vanillin reduction activity than control. In addition, overexpressing the ABC transporter genes <italic>PDR5, YOR1</italic>, and <italic>SNQ2</italic>, as well as the RNA helicase gene <italic>DBP2</italic>, increased the vanillin tolerance of strain. Interestingly, unlike the marked changes we mentioned above, under vanillin-free conditions, there are only limited transcriptional differences between wildtype and <italic>yrr1</italic>Δ. This indicated that vanillin might act as an effector in Yrr1p-related regulatory processes. The new findings of the relationship between <italic>YRR1</italic> and vanillin tolerance, as well as the contribution of rRNA processing and ribosome biogenesis to enhancing <italic>S. cerevisiae</italic> vanillin tolerance, provide novel targets for genetic engineering manipulation to improve microbes’ tolerance to lignocellulose hydrolysate.</p>