Data from: Gene expression differs in codominant prairie grasses under drought

Grasslands of the Central US are expected to experience severe droughts and other climate extremes in the future, yet we know little about how these grasses will respond in terms of gene expression. We compared gene expression in Andropogon gerardii and Sorghastrum nutans, two closely related co-dominant C4 grasses responsible for the majority of ecosystem function, using RNA-seq. We compared Trinity assemblies within each species to determine annotated functions of transcripts responding to drought. Subsequently, we compared homologous annotated gene-groups across the two species using cross-species meta-level analysis and functional clustering based on key terms. The majority of variation was found between species, as opposed to between drought and watered treatments. However, there is evidence for differential responses; Andropogon allocated gene expression differently compared to Sorghastrum, suggesting Andropogon focuses on stress alleviation (such as oxygen radical scavenging) rather than prevention. In contrast, Sorghastrum may employ a drought avoidance strategy by modulating osmotic response, especially with hormonal regulation. We found Sorghastrum tended to be more sensitive within 10 key gene-groups related to stress, abscisic acid, and trichomes, suggesting gene expression may mechanistically parallel sensitivity at the physiological level. Our findings corroborate phenotypic and physiological differences in the field, and may help explain the phenotypic mechanisms of these two species in the tallgrass prairie community under future drought scenarios.

美国中部草原未来或将遭遇严重干旱及其他极端气候事件，但目前学界对这类草本植物的基因表达响应机制仍知之甚少。本研究采用RNA测序（RNA-seq）技术，对两种亲缘关系密切的共优势C4草本植物——大须芒草(Andropogon gerardii)与垂穗假高粱(Sorghastrum nutans)的基因表达水平开展比较分析。这两种草本是支撑该生态系统绝大多数功能的关键类群。我们针对每个物种内部的Trinity组装结果进行比对，以明确干旱响应转录本的注释功能。后续，我们通过跨物种元层级分析与基于关键术语的功能聚类方法，对两个物种间的同源注释基因簇开展了比较研究。研究结果显示，绝大多数表达差异来源于物种间，而非干旱处理与正常浇水对照组之间。不过，仍有证据表明二者存在差异化响应：与垂穗假高粱相比，大须芒草的基因表达调控模式存在显著差异，提示大须芒草更侧重于胁迫缓解（如氧自由基清除）而非胁迫预防。与之相对，垂穗假高粱或可通过调控渗透响应，尤其是激素调控，采取干旱规避策略。我们发现，在与胁迫、脱落酸(abscisic acid)及表皮毛相关的10个关键基因簇中，垂穗假高粱的响应更为敏感，这表明基因表达的调控机制可能在生理层面与敏感性存在对应关系。本研究结果验证了野外观测到的表型与生理差异，或有助于阐释未来干旱情景下，高草草原群落中这两个物种种间差异的表型调控机制。