Transcriptome analysis of salt-responsive genes and SSR marker exploration in Carex rigescens using RNA-seq

Carex rigescens (Franch.) V. Krecz is a wild turfgrass perennial species in the Carex genus that is widely distributed in salinised areas of northern China. To investigate genome-wide salt-response gene networks in C. rigescens, transcriptome analysis using high-throughput RNA sequencing on C. rigescens exposed to a 0.4% salt treatment (Cr_Salt) was compared to a non-salt control (Cr_Ctrl). In total, 57 742 546 and 47 063 488 clean reads were obtained from the Cr_Ctrl and Cr_Salt treatments, respectively. Additionally, 21 954 unigenes were found and annotated using multiple databases. Among these unigenes, 34 were found to respond to salt stress at a statistically significant level with 6 genes up-regulated and 28 downregulated. Specifically, genes encoding an EF-hand domain, ZFP and AP2 were responsive to salt stress, highlighting their roles in future research regarding salt tolerance in C. rigescens and other plants. According to our quantitative RT-PCR results, the expression pattern of all detected differentially expressed genes were consistent with the RNA-seq results. Furthermore, we identified 11 643 simple sequence repeats (SSRs) from the unigenes. A total of 144 amplified successfully in the C. rigescens cultivar Luping 1, and 69 of them reflected polymorphisms between the two genotypes tested. This is the first genome-wide transcriptome study of C. rigescens in both salt-responsive gene investigation and SSR marker exploration. Our results provide further insights into genome annotation, novel gene discovery, molecular breeding and comparative genomics in C. rigescens and related grass species.