The non-conventional yeast Kluyveromyces marxianus has recently emerged as a promising candidate for many food, environment, and biotechnology applications. This yeast is thermotolerant and has robust growth under many adverse conditions. Here, we show that its ability to grow under potassium-limiting conditions is much better than that of Saccharomyces cerevisiae, suggesting a very efficient and high-affinity potassium uptake system(s) in this species. The K. marxianus genome contains two genes for putative potassium transporters: KmHAK1 and KmTRK1. To characterize the products of the two genes, we constructed single and double knock-out mutants in K. marxianus and also expressed both genes in an S. cerevisiae mutant, that lacks potassium importers. Our results in K. marxianus and S. cerevisiae revealed that both genes encode efficient high-affinity potassium transporters, contributing to potassium homeostasis and maintaining plasma-membrane potential and cytosolic pH. In K. marxianus, the presence of HAK1 supports growth at low K+ much better than that of TRK1, probably because the substrate affinity of KmHak1 is about 10-fold higher than that of KmTrk1, and its expression is induced ~80-fold upon potassium starvation. KmHak1 is crucial for salt stress survival in both K. marxianus and S. cerevisiae. In co-expression experiments with ScTrk1 and ScTrk2, its robustness contributes to an increased tolerance of S. cerevisiae cells to sodium and lithium salt stress.

• MeSH
• draslík * metabolismus   MeSH
• fungální proteiny genetika   metabolismus   MeSH
• genový knockout MeSH
• Kluyveromyces * genetika   metabolismus   růst a vývoj   MeSH
• koncentrace vodíkových iontů MeSH
• membránové potenciály MeSH
• proteiny přenášející kationty * genetika   metabolismus   MeSH
• regulace genové exprese u hub MeSH
• Saccharomyces cerevisiae * genetika   metabolismus   růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH