Thermal adaptation in closely related virbios. Thermal adaptation in closely related virbios

Here, we investigate the genetic mechanisms that underlie thermal specialization of closely-related vibrios isolated from coastal water at the Beaufort Inlet (Beaufort, NC, USA). This location experiences large seasonal temperature fluctuations (annual range of ~20°C), and a clear seasonal shift in vibrio diversity has been observed (Yung et al. 2015). This previous study suggested that the mechanisms of thermal adaptation apparently differ based on evolutionary timescale: shifts in the temperature of maximal growth occur between deeply branching clades but the shape of the thermal performance curve changes on shorter time scales (Yung et al. 2015). The observed thermal specialization in vibrio populations over relatively short evolutionary time scales indicates that few genes or cellular processes may contribute to the differences in thermal performance between populations. In order to understand the molecular mechanisms that underlie adaptation to local thermal regimes in environmental vibrio populations, we employ genomic and transcriptomic approaches to examine transcriptomic changes that occur within strains grown at their thermal optima and under heat and cold stress. Moreover, we compare two closely-related strains with different laboratory thermal preferences to identify in situ evolutionary responses to different thermal environments in genome content and alleles as well as gene expression. Overall design: We sequenced the transcriptomes of two environmental strains (Vibrio sp. PID17_43 and Vibrio sp. PID23_8) grown under three temperature conditions: heat stress, temperature of optimal growth and cold stress. The draft genome assemblies were deposited in the NCBI whole genome shotgun archive under project ID PRJNA292554, However, the WGS submission has not been released yet.

本研究聚焦于从美国北卡罗来纳州博福特入海口（Beaufort Inlet，北卡罗来纳州博福特市，美国）沿岸海域分离得到的近缘弧菌（Vibrio）的热适应性特化遗传机制。该海域存在显著的季节性温度波动，年温差约20℃，此前已有研究（Yung等，2015）观测到弧菌群落多样性存在明确的季节性更替现象。
该前期研究指出，热适应的分子机制随进化时间尺度存在显著差异：深度分支演化支间的最适生长温度发生分化，而热性能曲线的形态则在更短的时间尺度上发生改变（Yung等，2015）。为阐明环境弧菌种群适应局域热环境的分子机制，本研究采用基因组学（genomics）与转录组学（transcriptomics）方法，分析菌株在最适生长温度、热胁迫与冷胁迫条件下的转录组变化。
此外，本研究选取两株实验室热偏好存在差异的近缘弧菌菌株，通过对比其基因组组成、等位基因差异与基因表达模式，解析它们针对不同热环境的原位演化响应。
实验设计：本研究对两株环境分离弧菌（*Vibrio* sp. PID17_43与*Vibrio* sp. PID23_8）进行转录组测序，这些菌株分别在热胁迫、最适生长温度与冷胁迫三种温度条件下培养。该研究的基因组草图已以项目编号PRJNA292554提交至NCBI全基因组鸟枪法存档库，但目前WGS提交内容尚未公开。