Caspeta Luis, Chen Yun, Nielsen Jens
Centro de Investigación en Biotecnología, Universidad Autónoma del Estado de Morelos, MX-62209, Cuernavaca, Morelos, México.
Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
Sci Rep. 2016 May 27;6:27003. doi: 10.1038/srep27003.
Exposure to long-term environmental changes across >100s of generations results in adapted phenotypes, but little is known about how metabolic and transcriptional responses are optimized in these processes. Here, we show that thermotolerant yeast strains selected by adaptive laboratory evolution to grow at increased temperature, activated a constitutive heat stress response when grown at the optimal ancestral temperature, and that this is associated with a reduced growth rate. This preventive response was perfected by additional transcriptional changes activated when the cultivation temperature is increased. Remarkably, the sum of global transcriptional changes activated in the thermotolerant strains when transferred from the optimal to the high temperature, corresponded, in magnitude and direction, to the global changes observed in the ancestral strain exposed to the same transition. This demonstrates robustness of the yeast transcriptional program when exposed to heat, and that the thermotolerant strains streamlined their path to rapidly and optimally reach post-stress transcriptional and metabolic levels. Thus, long-term adaptation to heat improved yeasts ability to rapidly adapt to increased temperatures, but this also causes a trade-off in the growth rate at the optimal ancestral temperature.
历经100多代的长期环境变化会导致适应性表型的出现，但对于这些过程中代谢和转录反应是如何优化的，我们却知之甚少。在此，我们表明，通过适应性实验室进化筛选出的能够在升高温度下生长的耐热酵母菌株，在最佳祖先温度下生长时会激活一种组成型热应激反应，且这与生长速率降低有关。当培养温度升高时，通过激活额外的转录变化，这种预防性反应得以完善。值得注意的是，耐热菌株从最佳温度转移到高温时激活的全局转录变化总和，在幅度和方向上与暴露于相同转变的祖先菌株中观察到的全局变化相对应。这证明了酵母转录程序在受热时的稳健性，并且耐热菌株简化了它们快速且最佳地达到应激后转录和代谢水平的途径。因此，长期的热适应提高了酵母快速适应温度升高的能力，但这也在最佳祖先温度下的生长速率方面造成了权衡。
