Myristate (C14:0) is an essential multi-functional fatty acid in a variety of organisms. We found that C14:0, but not other fatty acids, causes severe growth retardation in Hpelo1Δ and Hpelo2Δ mutants of the yeast Hansenula polymorpha, defective in elongation of very long-chain fatty acids. While transcription of HpELO1 and HpELO2 is transiently increased by C14:0, this was not found to be responsible for the growth retardation. Transcription of HpFAS1 and HpFAS2 encoding fatty acid synthase is repressed by C14:0, but this repression was also not found to be responsible for growth retardation. A screen for suppressors that resulted in restored growth of the Hpelo1Δ disruptant on media containing C14:0 identified two types of suppressors. One exhibited a defect in C14:0 uptake while the other did not. Molecular genetic and genomic analysis of these suppressor mutations is anticipated to shed new light on the processes of fatty acid transport and the crucial role of C14:0 in the growth of eukaryotic organisms.
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