De novo transcriptome sequencing and analysis of salt-, alkali-, and drought-responsive genes inSophora alopecuroides

Background Salinity, alkalinity, and drought stress are the main abiotic stress factors affecting plant growth and development.Sophora alopecuroidesL., a perennial leguminous herb in the genusSophora, is a highly salt-tolerant sand-fixing pioneer species distributed mostly in Western Asia and northwestern China. Few studies have assessed responses to abiotic stress inS. alopecuroides. The transcriptome of the genes that confer stress-tolerance in this species has not previously been sequenced. Our objective was to sequence and analyze this transcriptome. Results Twelve cDNA libraries were constructed in triplicate from mRNA obtained fromSophora alopecuroidesfor the control and salt, alkali, and drought treatments. Using de novo assembly, 902,812 assembled unigenes were generated, with an average length of 294 bp. Based on similarity searches, 545,615 (60.43%) had at least one significant match in the Nr, Nt, Pfam, KOG/COG, Swiss-Prot, and GO databases. In addition, 1673 differentially expressed genes (DEGs) were obtained from the salt treatment, 8142 from the alkali treatment, and 17,479 from the drought treatment. A total of 11,936 transcription factor genes from 82 transcription factor families were functionally annotated under salt, alkali, and drought stress, these includeMYB,bZIP,NACandWRKYfamily members. DEGs were involved in the hormone signal transduction pathway, biosynthesis of secondary metabolites and antioxidant enzymes; this suggests that these pathways or processes may be involved in tolerance towards salt, alkali, and drought stress inS. alopecuroides. Conclusion Our study first reported transcriptome reference sequence data inSophora alopecuroides,a non-model plant without a reference genome. We determined digital expression profile and discovered a broad survey of unigenes associated with salt, alkali, and drought stress which provide genomic resources available forSophora alopecuroides.