Positive genetic interactors of HMG2 identify a new set of genetic perturbations for improving sesquiterpene production in Saccharomyces cerevisiae

Codruta Ignea,Antonios M Makris,Angelos K Kanellis,Anagnostis Argiriou,Ioannis Kourtzelis,Sotirios C Kampranis,Fotini A Trikka

doi:10.1186/1475-2859-11-162

Abstract

BackgroundTerpenoids and isoprenoids are an important class of natural products, which includes currently used drugs, high value bioactive and industrial compounds, and fuel candidates. Due to their industrial application, there is increasing interest in the development of S. cerevisiae strains capable of producing high levels of terpenoids.ResultsAiming to identify new gene targets which can be manipulated to increase sesquiterpene production, a set of HMG2 positive genetic interactors were assessed as single and digenic heterozygous deletions in the presence or absence of stable HMG2(K6R) overexpression. Upon single allele deletion, most genes examined led to increased sesquiterpene production in yeast cells. Tandem heterozygous deletion of a set of three genes, the ubiquitin ligases ubc7 and ssm4/doa10, and the ER resident protein pho86, led to an 11-fold increase in caryophyllene yields (125 mg/L in shake flasks) compared to cells lacking these modifications. The effect of the heterozygous deletions appears to be due to Hmg1p and Hmg2p stabilization.ConclusionHeterozygous deletions cause significant reductions in protein levels but do not lead to growth impediments frequently seen in haploid strains. By exploiting desirable haploinsufficiencies in yeast, we identified a new set of genes that can be disrupted in tandem and cause significant stabilization of Hmgp and a substantial increase in sesquiterpene production. The approach presented here allows new genetic perturbations to be compiled on yeast cell factory strains without negatively impacting cell growth and viability.

Highlights

Terpenoids and isoprenoids are an important class of natural products, which includes currently used drugs, high value bioactive and industrial compounds, and fuel candidates
Genetic analysis have identified Ubiquitin ligase components (HRD1 and HRD3), which function alongside a distinct Endoplasmic Reticulum Associated Degradation (ERAD) pathway, to be associated with regulated degradation of Hmgp [4,5,6]
A group of yeast strains deleted for genes previously identified as HMG2 positive genetic interactors was selected, reasoning that under conditions of high terpene precursor production which impose stress on the mevalonic acid (MVA) pathway, cells would be stressed in a similar manner to hmg2 deletion, and their deletion could alleviate such stress (Figure 1)

Summary

Introduction

Terpenoids and isoprenoids are an important class of natural products, which includes currently used drugs, high value bioactive and industrial compounds, and fuel candidates. Due to their industrial application, there is increasing interest in the development of S. cerevisiae strains capable of producing high levels of terpenoids. Terpenoids and isoprenoids constitute an important class of secondary metabolites that contributes more than 50,000 compounds [2] to the rich chemical diversity of natural product structures. They include drugs, high-value bioactive and industrial compounds, and fuel candidates. The Doa10p (SSM4) Ubiquitin ligase plays a central role in the ERAD pathway by mediating the degradation of a variety of misfolded ER proteins

Methods

Results

Discussion

Conclusion