Genome-Wide Identification and Expression Analysis of SnRK Gene Family under Abiotic Stress in Cucumber (Cucumis sativus L.)

Sucrose non-fermenting 1-related protein kinases (SnRKs) are a kind of plant-specific serine/threonine (Ser/Thr) protein kinase, which play an important role in plant stress resistance. However, the scale analysis of SnRK in the cucumber genome is currently unclear. In the study, a total of 30 CsSnRK genes were identified from genomic data. They were distributed on six chromosomes, including 1 CsSnRK1, 10 CsSnRK2s and 19 CsSnRK3s. According to the analysis of gene structure and motif composition, CsSnRKs showed obvious differences among the three subfamilies. The ratio of synonymous (Ks) and nonsynonymous (Ka) nucleotide substitutions (Ka/Ks) of three paralogues indicates that the CsSnRK gene family undergoes a purifying selection. The analysis of cis-acting elements shows that the promoter region of each CsSnRK gene contained different classes of hormone and stress-related cis-acting elements. Furthermore, based on RNA-sequencing data from the Short Read Archive (SRA) database of NCBI, the expression patterns of CsSnRK genes in six tissues were investigated, indicating that the expression of multiple CsSnRK genes was prevalent in these tissues. Transcription levels of CsSnRK genes after drought, methyl jasmonate (MeJA) and abscisic acid (ABA) treatments were analyzed by quantitative RT-PCR, and the results show that most of the CsSnRK genes responded to these stresses. However, under different treatments, individual genes played a major role. For example, under ABA treatment, CsSnRK2.2 and CsSnRK2.3 played a major role in the response to ABA. These results provide clear evidence that CsSnRKs may be involved in cucumber growth, development and stress response, and provide valuable information for future functional studies of CsSnRKs.