In Pichia pastoris, growth rate regulates protein synthesis and secretion, mating and stress response

Abstract

Protein production in yeasts is related to the specific growth rate μ. To elucidate on this correlation, we studied the transcriptome of Pichia pastoris at different specific growth rates by cultivating a strain secreting human serum albumin at μ = 0.015 to 0.15 h-1 in glucose-limited chemostats. Genome-wide regulation revealed that translation-related as well as mitochondrial genes were upregulated with increasing μ, while autophagy and other proteolytic processes, carbon source-responsive genes and other targets of the TOR pathway as well as many transcriptional regulators were downregulated at higher μ. Mating and sporulation genes were most active at intermediate μ of 0.05 and 0.075 h-1. At very slow growth (μ = 0.015 h-1) gene regulation differs significantly, affecting many transporters and glucose sensing. Analysis of a subset of genes related to protein folding and secretion reveals that unfolded protein response targets such as translocation, endoplasmic reticulum genes, and cytosolic chaperones are upregulated with increasing growth rate while proteolytic degradation of secretory proteins is downregulated. We conclude that a high μ positively affects specific protein secretion rates by acting on multiple cellular processes. Protein production in yeast is related to cellular growth rate. In this study the authors investigated the regulation of all genes in the yeast Pichia pastoris at a wide range of growth rates, and showed that genes related to protein synthesis and protein folding are upregulated with increasing growth rate, while protein degradation is downregulated. Genes related to sexual reproduction of the yeast are most active at intermediate growth rate. The authors conclude that faster growth positively affects protein secretion related to multiple cellular processes. © 2014 The Authors. Biotechnology Journal published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.