Physiological and transcriptional responses to drought stress and recovery in a drought-tolerant fescue wild grass (Festuca ovina; Poaceae)

Water stress associated with drought-like conditions is a major factor limiting plant growth and impacts productivity of natural plant communities and agricultural crops. Molecular and physiological responses of plants to water stress have been studied most extensively in model species and crops, few of which have evolved natural drought tolerance. In the current study, we examined physiological and transcriptomic responses at multiple timepoints during increasing water stress and following initial recovery from stress in a drought-tolerant C3 species, Festuca ovina. Results demonstrated a largely linear decline in physiological measures during increasing water stress but non-linear transcriptomic changes, with the largest gene expression changes associated with entering, and exiting, highest physiological stress. Global gene expression profiles revealed up-regulated genes over-represented by Gene Ontology (GO) terms such as response to abiotic stress, response to abscisic acid (ABA), and response to hormone; down-regulated genes were over-represented by categories such as cell wall organization, multidimensional cell growth, and photosynthesis. Transcription factors represented approximately 12.7% of all differentially expressed genes. This information will be valuable for further investigations of the molecular mechanisms involved in drought tolerance in C3 plants.与类干旱环境相关的水分胁迫（water stress）是限制植物生长、影响自然植物群落与农业作物生产力的关键因素。针对植物对水分胁迫的分子与生理响应，现有研究多集中于模式物种与农作物，但其中极少演化出天然耐旱特性。本研究以耐旱型C3植物细叶羊茅（Festuca ovina）为材料，探究了其在梯度水分胁迫过程中以及胁迫初始恢复阶段多个时间点的生理与转录组响应。结果显示，梯度水分胁迫下生理指标大体呈线性下降趋势，但转录组变化呈现非线性特征，最大规模的基因表达变化出现在进入以及脱离最高生理胁迫状态的节点。全局基因表达谱分析显示，上调基因显著富集于基因本体（Gene Ontology，GO）注释条目，如非生物胁迫响应、脱落酸（abscisic acid，ABA）响应以及激素响应等；下调基因则显著富集于细胞壁组织、多维细胞生长以及光合作用等功能类别。转录因子占所有差异表达基因的约12.7%。本研究获得的相关信息将为后续探究C3植物耐旱性的分子机制提供重要参考。