RNA-seq differential expression analysis of Komagataella phaffii CBS2612 under mating conditions
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ABSTRACT: We used RNA sequencing to analyse the differences in gene expression between the homothallic K. phaffii CBS2612 wild type and heterothallic a- and α-type strains during growth in rich medium and under mating conditions. This data was used to investigate mating-type specific gene expression and allowed the identification of the K. phaffii a-factor genes.
Project description:The yeast Komagataella phaffii is a promising alternative host for manufacturing of therapeutic proteins. Deletion of unneeded endogenous proteins could increase the secreted titer of recombinant proteins by redirecting cellular resources. Genetic engineering in non-model hosts is hampered by limited annotation of genes, especially essential genes. In this study, we identified the set of endogenous secreted proteins in K. phaffii and attempted to disrupt these genes. We designed, transformed, and sequenced a pooled CRISPR-Cas9 knockout library to determine which genes are essential. With this knowledge, we rapidly disrupted up to 9 consecutive genes in K. phaffii. Engineered strains exhibited a ~20x increase in the production of human serum albumin and a 2x increase in the production of a monoclonal antibody. The pooled CRISPR-Cas9 library and knowledge of gene essentiality reported here will facilitate future efforts to engineer K. phaffii for production of other recombinant therapeutic proteins and enzymes.
Project description:The protein production host Komagataella phaffii has possess the ability to differentiate into pseudohyphal form when cultivated at slow growth rates (µ=0.05 h-1) in glucose-limited chemostats. In this study, we investigated the K. phaffii FLO gene family in the context of pseudohyphae formation. Transcriptional analysis helped us identify 3 possible responsible genes, FLO11, FLO400 and FLO5-1, all of which are under control of Flo8, a transcription factor whose disruption prevents pseudohyphae formation. Knocking out FLO11 revealed that this is not the sole protein responsible for this phenotype. Strikingly, the expression of FLO400 and FLO5-1 was negatively correlated with pseudohyphae formation, and shown to be under epigenetic control by FAIRE-Seq analysis. Knock outs of these two genes completely inhibited the appearance of pseudohyphal cells and prevented the expression of FLO11. Even though the mechanism is unclear at present, we propose that in K. phaffii Flo400 and/or Flo5-1 act as upstream signals that lead to the induction of FLO11 expression upon severe glucose limitation in chemostats at slow growth rate, and that the expression of FLO400 and FLO5-1 is controlled by epigenetic silencing, which acts independently from the general activation of FLO gene expression by the transcriptional regulator Flo8.