Abstract: 【Objective】The objective of this study is to understand the inner molecular mechanisms of Saccharum spontaneumclone named Yunnan 82-114 in response to water stress, and mine these genes closely related to drought tolerance, improve the utilization efficiency of Saccharum spontaneum in sugarcane drought-resistant breeding program. 【Method】llumina HiSeqTM 4000, a high-through transcriptome sequencing technology, was applied to obtain the transcriptome differential expression data of Yunnan82-114 roots under drought stress treatment for 24h, 48h, and 72h. These assembled unigenes above were compared with database of Swiss-Prot, Nr, KOG, Pfam, and KEGG, respectively, then the abundance of gene expression among different samples were screened according to transcriptome data by using RPKM method, and the differentially expressed genes among the treated samples were estimated by referring to the standard of FDR≤0.05 & |log2 fold change|≥1. Function and pathway of those different expression genes were also investigated using Gene Ontology（GO）database and KEGG pathway database.【Result】Total 134 724, 130 368, 133 564, and 131 321 expressing genes were got, respectively, from the untreated control and three treated samples(24 h, 48 h and 72 h). Compared the control with the treated samples, about 3 061 (1 302), 2 304 (2 841) and 3 236 (2525) genes whose expression was significantly up-regulated (or down-regulated) were detected, respectively. When the FDR value was set to be 0 as a selection criterion, some genes performing extreme significantly different expression between control and treated samples were acquired, they mainly involved in transcriptional activation, water transport, DNA binding, ATP binding, membrane/ transmembrane transport, and defense response. GO enrichment analysis showed that some differences in the biological approach categories existed among the treated samples, for the samples treated for 24 h and 48h, the most enriched category was DNA-dependent transcription and transcription factor, then to the samples treated for 72 h, the enriched category was the translation-related genes. At the aspects of cellular components and molecular functions, the enriched category was inner membrane, nucleus, and ATP binding related genes in the three treated samples. KEGG enrichment analysis illustrated that 2 248 differentially expressed genes involved in 107 pathways in 24 h-treated sample, 2 114 in 130 in 48h-treated sample, and 2 392 in 144 in 72 h-treated sample. Finally, some genes related to abiotic stress and resistance were screened via KEGG significance enrichment analysis, which include glycosylsphingolipid biosynthesis, MAP kinase signal transduction, and ABC translocator.【Conclusion】Expression pattern and function information of differentially expressed genes between three water-stressed samples and a control were analyzed. Some genes like extracellular signal-regulated kinase, phospholipase D, hexosaminidase, and ATP-binding cassette B-1 were found to involve in response to water stress for Yunnan82-114. About 70 significant up-regulated expression genes at transcription level were obtained, but there were 11 genes exhibiting down-regulated expression, this implied that these genes induced or suppressed fiercely by drought stress have obvious relationships with drought tolerance of Yunnan82-114.

Key words: Saccharum spontaneum, drought, transcriptomes, differentially expressed genes