GSE62174
Transcriptome analysis of the primary roots of Alhagi sparsifolia in response to water stress
Alhagi sparsifolia Shap. is a perennial subshrub belonging to genus Alhagi, family Leguminosae. As a typical desert phreatophyte, this plant species has highly developed deep roots and displays a great capacity to withstand poor soil as well as extreme dry, cold and hot weather. A. sparsifolia is naturally distributed in the arid and salinized regions of northernwestern China and adjacent countries in Central Asia, and plays a fundamental role in maintaining the local ecosystem. In addition, this plant is usually used as a fodder for local animals due to its high protein content, and is important in the development of local livestock husbandry. Considering its great tolerance to harsh environments, A. sparsifolia represents an ideal species for deciphering the mechanism of plant adaption to abiotic stress, such as water deficit. However, understanding the stress adaption in this plant is limited. While a few studies were conducted on physiological responses of A. sparsifolia to water stress, research has never been done to explore the genomic basis for its drought-tolerance to date. In particular, as a non-model plant species, the genomic resource of A. sparsifolia is rather scarce, only one expressed sequence tag (EST) and one protein have been deposited in Genbank prior to Sept., 2014.   In aim to explore the genetic basis underlying drought tolerance in this species, recently we took advantage of transcriptome sequencing to survey the water stress responsive genes in A. sparsifolia primary roots. Using Illumina HiSeq™ 2000 platform, we sequenced the primary root samples individually collected at four different time points (0, 6h, 24 and 30h) from A. sparsifolia seedlings during 24h of water stress following 6h of rehydration. The resulting 38,763,230, 67,511,150, 49,259,804 and 54,744,906 high quality reads were pooled and assembled into 33,255 unigenes with an average length of 1,057 bp. All-unigenes were subjected to functional annotation by searching against the public databases including NR, NT, Swiss-Prot, Pfamm, GO, KOG and KEGG. On the basis of the established transcriptome database, we evaluated the gene expression profiles in A. sparsifolia primary roots at 0, 6, 24 and 30h in the course of water stress and subsequent rehydration. An extensive repertoire of the differently expressed genes (DEGs) reflecting the early response to water stress (6h), the late response to water stress (24h) and the response to post stress rehydration (30h) were identified. In addition, to unravel the dynamic changes of gene expression during water stress and subsequent rehydration, we further captured the DEGs commonly or specifically regulated at 6, 24 and 30h. Functional categorization of the DEGs disclosed the activation of oxidoreductase system in A. sparsifolia primary roots upon water stress, and particularly emphasized the significance of the ‘Glutathione metabolism pathway’.          To our knowledge, this is the first description of the genetic makeup of A. sparsifolia, thus providing a substantial contribution to the sequence resources for this species. The DEGs identified herein offers a deep insight into the molecular mechanism of A. sparsifolia in response to water stress, and merits further investigation. Overall design: Identification of the differently expressed genes during 24h of water stress following 6h of rehydration in A. sparsifolia