Transcriptomic analysis of sorghum genotypes in response to drought stress

Drought is a major limiting factor of crop yields. In response to drought, plants reprogram their gene expression, which ultimately regulates a multitude of biochemical and physiological processes. The timing of this reprogramming and the nature of the drought-regulated genes in different genotypes are thought to confer differential tolerance to drought stress. At the molecular level, the responses include gene regulation at the transcriptional level. Sorghum is a highly drought-tolerant crop and has been increasingly used as a model cereal to identify genes that confer tolerance. Also, there is considerable natural variation in resistance to drought in different sorghum genotypes. Here, we performed transcriptomic analysis in seedlings of sorghum genotypes that are either drought-resistant or drought-sensitive to identify drought-induced changes in gene expression that are unique to drought-resistant genotypes of sorghum. Our analysis revealed about 180 drought-regulated genes only in drought-resistant genotypes and most of these (over 70%) are up-regulated in response to drought. Among these, about 70 genes are novel with no known function and the remaining are transcriptions factors, signaling and stress-related proteins implicated in drought tolerance in other crops. This study revealed a set of genes including many genes encoding uncharacterized proteins that are associated with drought tolerance at the seedling stage.

干旱是制约作物产量的关键非生物胁迫因子。当遭遇干旱胁迫时，植物会启动基因表达重编程程序，最终调控一系列复杂的生化与生理过程。现有研究认为，这类重编程的时序以及不同基因型中干旱调控基因的特性，决定了植株对干旱胁迫的差异化耐受能力。在分子层面，植物的干旱响应包含转录水平的基因调控。高粱（Sorghum）是一类高度耐旱的作物，正日益被用作模式谷类作物，用于鉴定赋予作物耐旱性的相关基因。同时，不同高粱基因型间的耐旱性存在显著的自然遗传变异。本研究针对耐旱型与敏感型两种高粱基因型的幼苗开展转录组分析，旨在鉴定仅在耐旱型高粱中特异性存在的干旱诱导基因表达变化。分析结果显示，仅在耐旱型高粱中被干旱调控的基因约有180个，其中超过70%的基因在干旱胁迫下呈现表达上调。在这些基因中，约70个为功能未知的新基因，其余则为转录因子、信号通路相关蛋白以及其他作物中已被证实与耐旱性相关的胁迫响应蛋白。本研究鉴定得到一组与高粱幼苗期耐旱性相关的基因，其中包含大量功能未被注释的蛋白编码基因。