Identification and expression analyzes of CC-type glutaredoxin in cucumber (Cucumis sativus L.) under abiotic stress

Glutaredoxins (GRXs) are key regulators in the cellular redox state and play pivotal roles in both plant development and responses to stress stimuli. Here, we found 45 GRX gene members in cucumber, 16 of which were classified as CC-type. These CC-type GRXs were shown to be highly conserved among cucumber, Arabidopsis thaliana, and rice, according to our bioinformatic analyzes results. Cucumber CC-type GRX (CsGRX) genes showed varying expression levels in different plant organs and in response to different abiotic stresses. CsGRX1, CsGRX5, CsGRX9, CsGRX13, and CsGRX16 expression was induced from 3 to 6 h by salicylic acid (SA) treatments, whereas CsGRX1, CsGRX3, CsGRX8, CsGRX13, CsGRX14, and CsGRX17 expression was induced from 3 to 12 h with methyl jasmonate (MeJA) treatments. Moreover, CsGRX11 expression was strongly induced from 0 to 24 h by MeJA treatment, whereas CsGRX3 and CsGRX11 expression was strongly induced at the early stages of 42 degrees C treatments and at the later stages of the methyl viologen treatments. CsGRX4, CsGRX6, CsGRX7, CsGRX13 and CsGRX11 expression was induced by PEG and NaCl treatments. These results indicated the versatile roles of GRX genes in response to stress stimuli. The subcellular localization results for three CsGRX-green fluorescent protein (GFP) fusion proteins indicated that some orthologs were localized to the nucleus. CsGRX4 that responded to salt stress were heterologously expressed in Arabidopsis, and its transgenic lines demonstrated salt sensitivity, showing lower seed germination rate and shorter root length than their wild type counterparts under salt stress. Our results provide a foundation for future studies on GRX genes in cucumber.