甜高粱作为重要的潜在能源作物之一，其应用主要是利用茎秆中的糖，但目前有关高粱茎秆糖积累的分子机制尚不清楚。microRNA是调控植物生长发育和胁迫等生物过程的重要因子之一，为研究microRNA是否参与糖积累的调控，我们比较了甜高粱和粒用高粱在抽穗期和蜡熟期的叶片和茎秆中microRNA的表达差异，筛选到一个在甜高粱茎秆蜡熟期特异表达的新microRNA(暂命名novel-mir271)。为进一步研究该microRNA在甜高粱糖积累中的作用，本项目拟开展如下研究：利用novel-mir271在200份甜高粱和粒用高粱材料中的表达特性分析，确定其与糖积累的相关性；利用降解组测序技术鉴定其靶基因，检测靶基因表达特性，并转化验证基因功能，分析靶基因在糖积累过程中的作用，从而阐明microRNA对甜高粱茎秆糖积累的调控机制。该研究将在甜高粱茎秆糖积累如何在RNA水平进行调控的研究上取得突破进展。

Sweet sorghum is a promising crop for biofuel production; sugars in its stalks are mainly used for ethanol fermentation. However, molecular mechanism of sugar accumulation in sorghum stalks has not been clear. MicroRNAs have been proved to play crucial roles in plant growth, development and stress response. In order to identify which microRNAs involve in sugar accumulation in sorghum stalks, eight libraries of small RNAs were constructed using samples from different sugar accumulation stage for high-throughput sequence. Total RNA of sweet sorghum (Rio) and grain sorghum (BTx623) were extracted from different tissues (stems and leaves) at the heading and dough stage. High-throughput sequencing was used to identify known microRNAs and novel microRNAs of sugar accumulation in the stem of sorghum. Our results showed that a novel microRNA (named novel-mir271), which specifically expressed in stem of sweet sorghum at dough stage. In order to validate the role of novel-mir271 in sweet sorghum sugar accumulation, this project plans to carry out the following research. First, expression pattern of novel-mir271 will be analyzed in 200 sorghum varieties using stem-loop RT-qRCR technology. Second, degradome sequencing technology will be used to identify target genes of novel-mir271. Detection of target genes expression trait and gene functions will help to illuminate the role of target genes in sugar accumulation process, so as to clarify microRNA regulatory mechanism of sweet sorghum stalks in sugar accumulation. This study will make breakthroughs on sugar accumulation of sweet sorghum in RNA regulation level.