Identification of drought response genes by digital gene expression (DGE) analysis in Caragana korshinskii Kom.

Caragana korshinskii Kom. is a legume shrub that is widely distributed across desert habitats with gravely, sandy, and saline soils in Asia and Africa. C. korshinskii has highly developed roots and a strong tolerance to abiotic stress. At present, there are few genetic studies of C. korshinskii because of the limited availability of genomic resources. To understand the comprehensive mechanisms that are associated with drought tolerance, we used RNA-seq to survey the differentially expressed genes (DEGs) in comparisons of drought-treated and control plants. After analysing the sequencing results, we found 440 differentially expressed genes existing in drought-treated and control plants. Among the DEGs, 39 unigenes showed up-regulated expression after drought treatment, while 401 unigenes were down-regulated. We used the KEGG database to annotate these drought-induced genes; 126 unigenes were identified by KEGG pathway annotation, and approximately 28% of the unigenes with known function fell into categories related to fatty acid metabolism, starch, sucrose metabolism, and nitrogen metabolism, suggesting that these pathways or processes may be involved in the drought response. Finally, we confirmed that one gene has a potential function in drought tolerance. Our study is the first to provide transcriptomic resources for Caragana korshinskii and to determine its digital gene expression profile under conditions of drought stress using the assembled transcriptomic data for reference. These data provide a valuable resource for genetic and genomic studies of desert plants under abiotic stress conditions.