Background: Cells constantly adapt to changes in their environment. When environment shifts between conditions that were previously encountered during the course of evolution, evolutionary-programmed responses are possible. Cells, however, may also encounter a new environment to which a novel response is required. To characterize the first steps in adaptation to a novel condition, we studied budding yeast growth on xylulose, a sugar that is very rarely found in the wild. Results: We previously reported that growth on xylulose induces the expression of amino acid biosynthesis genes in multiple natural yeast isolates. This induction occurs despite the presence of amino acids in the growth medium and is a unique response to xylulose, not triggered by naturally available carbon sources. Propagating these strains for ~300 generations on xylulose significantly improved their growth rate. Notably, the most significant change in gene expression was the loss of amino acid biosynthesis gene induction. Furthermore, the reduction in amino-acid biosynthesis gene expression on xylulose was tightly correlated with the improvement in growth rate, suggesting that internal depletion of amino-acids presented a major bottleneck limiting growth in xylulose. Conclusions: We discuss the possible implications of our results for explaining how cells maintain the balance between supply and demand of amino acids during growth in evolutionary 'familiar' vs. 'novel' conditions.
Bibliographical noteFunding Information:
We would like to thank Dr. Justin Fay for providing wild type S. cerevisiae strains. This work was supported by the NIH (P50GM068763), the European Research Council, the Israel Science Foundation, Azrieli award for innovative student proposals and the Helen and Martin Kimmel Award for Innovative Investigations. NB is the incumbent of the Lorna Greenberg Scherzer Professorial Chair, and the Minerva Foundation. YP acknowledges support of the Minerva Center for Live Emulation of Genome Evolution in the Lab. ZT is supported by the Israeli Ministry of Science and Technology. AHY is supported by the Human Frontier Science Program.
NIH, European Research Council, Israel Science Foundation, Helen and Martin Kimmel Award for Innovative Investigations, Minerva Center for Live Emulation of Genome Evolution in the Lab, Israeli Ministry of Science and Technology and Azrieli award for innovative student proposals.
© 2016 The Author(s).
- Amino-acid biosynthesis