Functional Analysis Of Wheat TaCKB4 In Photomorphogenesis And Response To Salt Stress

The growth and development of plants are affected by various environmental factors such as light,temperature,salt and drought.The complex crosstalk is embedded among the signaling pathways responsive to different environmental factors,which coordinate the of plant growth and crop yield.In recent years,we have had a deeper understandregulation ing of the response mechanism of plant salt stress,but there is still a lack of research on the orchestration between signals of salt stress and photosynthesis.Therefore,it is necessary to further explore the interactive features of the light and salt stress response process and identify the key interactive node regulatory factors.In our laboratory,the asymmetric somatic hybridization technology was used to cultivate the introgressive salt-tolerant new variety Shanrong 3(SR3)of common wheat Jinan 177(JN177),and its salt tolerance during germination and plant growth stage was significantly improved.On the other hand,compared with JN177,SR3 plants grew more vigorously;seedlings grew faster after germination,coleoptiles were longer,and light morphogenesis capacity was weaker.A blue light-responsive transcription factor,TaGBF1,was identified in the laboratory.Its overexpression promoted blue-mediated photomorphogenesis and reduced salt tolerance by inducing ABI5 expression.However,the molecular mechanism by which TaGBF1 regulates these two processes is unclear.A CKII family gene TaCKB4 gene was identified from SR3 in our laboratory and its Arabidopsis overexpression strain was constructed.In this paper,the role of TaCKB4 in photomorphogenesis and abiotic stress responses was analyzed,and the relationship between TaCKB4 and TaGBF1 was analyzed.The results showed that under blue light conditions,TaCKB4 was significantly down-regulated in the aboveground part of wheat.Compared with the wild type,the hypocotyls of the TaCKB4 overexpressing line under white light significantly elongated,and more significantly under blue light,while there was no significant difference in the hypocotyl length under dark,red and far red light,indicating that TaCKB4 was shown to specifically inhibit blue light-mediated photomorphogenesis.Under white light and blue light,compared with the wild type,the hypocotyls of the blue receptor CRY1 overexpression were significantly shorter,and the hypocotyl length of the hybrid strain with the TaCKB4 overexpressing line was similar to the hypocotyl length of the TaCKB4 overexpressing line.The results showed that TaCKB4 is a negative regulator of blue light-mediated photomorphogenesis signaling pathway and can inhibit constitutive blue light morphogenesis.Previous studies in the laboratory have found that TaGBF1 was a positive regulator of blue light-mediated photomorphogenesis signal pathway,and it can specifically promote the blue-mediated photomorphogenesis.We found that the hypocotyls of the TaGBF1 overexpressing line were shorter in the white light and blue light than in the wild type,and the length of the hypocotyl of the hybrid strain with the TaCKB4 overexpressing line was longer but shorter than that of the TaCKB4 overexpressing line.Overexpression of TaGBF1 can inhibit the expression of AtCKB4,and TaGBF1 can bind to the G-box region of TaCKB4 promoter,indicating that TaCKB4 is the target gene of TaGBF1,and TaGBF1 may promote blue light-mediated photomorphogenesis by inhibiting TaCKB4.The same as TaGBF1,TaCKB4 is located in the nucleus,but TaGBF1 does not interact with TaCKB4,indicating that TaCKB4 does not function by phosphorylating TaGBF1.In contrast,there is a direct interaction between TaCKB4 and AtHY5,suggesting that TaCKB4 may inhibit blue light-mediated photomorphogenesis by phosphorylating AtHY5 and its wheat homologues.The results showed that the proportion of TaCKB4 overexpressing lines in open cotyledons decreased under salt stress,the germination rate slowed,and the germination rate decreased,indicating that,like TaGBF1,TaCKB4 also reduced salt tolerance during germination.The expression of some genes related to ion transport and ABA synthesis in TaCKB4 overexpressing lines was significantly down-regulated,indicating that TaCKB4 can reduce salt tolerance by negatively regulating ion transport and ABA pathway.Previous studies found that TaGBFl reduced salt tolerance by up-regulating ABI5.We found that under normal conditions,TaCKB4 overexpression decreased the expression of ABI5,while salt stress treatment increased the expression of ABI5,suggesting that TaCKB4 may participate in the salt stress response of plants by dually regulating the expression of ABI5.In summary,we demonstrated that TaCKB4 is a key regulator in the crossover pathways of light signaling and salt stress responses through phenotypic analysis of TaCKB4 under light and salt stress.