Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA, USA.
USDA Forest Service, Pacific Southwest Research Station, Davis, CA, USA.
Mol Ecol. 2019 Dec;28(24):5248-5264. doi: 10.1111/mec.15289. Epub 2019 Nov 19.
Drought is a major stress for plants, creating a strong selection pressure for traits that enable plant growth and survival in dry environments. Many drought responses are conserved species-wide responses, while others vary among populations distributed across heterogeneous environments. We tested how six populations of the widely distributed California valley oak (Quercus lobata) sampled from contrasting climates would differ in their response to soil drying relative to well-watered controls in a common environment by measuring ecophysiological traits in 93 individuals and gene expression (RNA-seq) in 42 individuals. Populations did not differ in their adjustment of turgor loss point during soil drying, suggesting a generalized species-wide response. Differential expression analysis identified 689 genes with a common response to treatment across populations and 470 genes with population-specific responses. Weighted gene co-expression network analysis (WGCNA) identified groups of genes with similar expression patterns that may be regulated together (gene modules). Several gene modules responded differently to water stress among populations, suggesting regional differences in gene network regulation. Populations from sites with a high mean annual temperature responded to the imposed water stress with significantly greater changes in gene module expression, indicating that these populations may be locally adapted to respond to drought. We propose that this variation among valley oak populations provides a mechanism for differential tolerance to the increasingly frequent and severe droughts in California.
干旱是植物面临的主要压力之一，这为那些能够使植物在干燥环境中生长和存活的特性施加了强大的选择压力。许多干旱响应是广泛存在于物种间的保守响应，而其他响应则因分布在异质环境中的种群而异。我们通过测量 93 个个体的生态生理特性和 42 个个体的基因表达（RNA-seq），测试了从具有不同气候的广泛分布的加利福尼亚山谷橡树（Quercus lobata）中选取的六个种群，在与充分供水对照相比，在共同环境中对土壤干燥的响应如何存在差异。种群在土壤干燥过程中调整膨压损失点方面没有差异，这表明存在广泛存在于物种间的一般性响应。差异表达分析确定了 689 个在种群间具有共同处理响应的基因和 470 个具有种群特异性响应的基因。加权基因共表达网络分析（WGCNA）确定了具有相似表达模式的基因的群组，这些基因可能一起受到调控（基因模块）。一些基因模块在种群之间对水分胁迫的响应不同，这表明基因网络调控存在区域差异。来自年平均温度较高的地点的种群对施加的水分胁迫有明显更大的基因模块表达变化，这表明这些种群可能对干旱有局部适应性。我们提出，山谷橡树种群之间的这种差异为加利福尼亚日益频繁和严重的干旱提供了不同耐受能力的机制。
