Degradome profiles in leaves of Sorghum exposed to drought or heat or their combination

MicroRNAs (miRNAs) are part of gene regulatory networks that direct all most all biological processes in plants including their growth and development, as well as adaptation to biotic and abiotic stresses. Sorghum is largely grown for its grain production, but recently it also emerged a major feedstock for biofuel production. Interestingly, Sorghum is relatively drought tolerant crop and largely grown in semi-arid tropical and sub-tropical regions where the drought or high temperature or their combination co-occur in the field. Although miRNA profiles have been reported in Sorghum leaves exposed to drought, but thus far miRNAs in heat- or drought and heat-exposed conditions have not been reported. In this study, we report miRNA profiles in Sorghum leaves exposed to drought or heat or their combination. The bioinformatic analysis of small RNA libraries revealed the expression of approximately 30 conserved miRNA families represented by 81 individual miRNAs as well as 11 novel miRNA families in Sorghum leaves. Of these, 26 miRNAs were found to be differentially regulated in response to one or more of the stress treatments. Overall, the number of miRNAs regulated by heat was more than the drought. Furthermore, miRNA profiles revealed more similarities between heat and the combination of drought and heat stresses. We also have analyzed degradome profiles in control and drought-exposed plants to identify potential targets for the miRNAs. This study provides a frame work for better understanding of miRNA-guided gene regulations that vary between individual drought or heat or combination of drought and heat treatments. Overall design: degradome sequencing profiles in Sorghum leaves exposed to drought or heat or their combination

微RNA（miRNAs）是基因调控网络的核心组分，可调控植物几乎所有生命过程，包括生长发育以及对生物和非生物胁迫的适应。高粱（Sorghum）主要以籽粒种植为核心用途，但近年来也逐渐成为生物燃料生产的重要原料作物。值得注意的是，高粱属于相对耐旱的作物，且广泛种植于半干旱热带及亚热带区域——这类田间环境常同时面临干旱、高温或二者复合胁迫。尽管已有研究报道了干旱胁迫下高粱叶片的miRNA表达谱，但截至目前，针对高温胁迫以及干旱-高温复合胁迫下的高粱miRNA表达谱尚未见公开报道。本研究对干旱、高温及其复合胁迫下的高粱叶片miRNA表达谱进行了系统分析。通过对小RNA文库的生物信息学分析，我们在高粱叶片中鉴定得到约30个保守miRNA家族（涵盖81个成熟miRNA）以及11个新发现的miRNA家族。其中，26个miRNA在一种或多种胁迫处理下呈现显著差异表达。总体而言，受高温胁迫调控的miRNA数量多于干旱胁迫。此外，miRNA表达谱分析显示，高温胁迫与干旱-高温复合胁迫的miRNA表达模式具有更高的相似性。我们还对对照组及干旱胁迫处理植株的降解组（degradome）谱进行了分析，以鉴定上述miRNA的潜在靶基因。本研究为深入理解干旱、高温及其复合胁迫下各自特异的miRNA介导基因调控机制提供了重要研究框架。实验设计概要：对干旱、高温及其复合胁迫下的高粱叶片开展降解组测序（degradome sequencing）分析