| Tomato(Solanum lycopersicum)is a kind of horticultural crop widely cultivated in China,which is rich in nutrition and has high added value.As a kind of thermophilic vegetable,tomato is sensitive to low temperature.The suitable growth temperature for tomato is between 20 to 25℃,which is important for the yield and quality.Therefore,it is of great significance to explore the mechanism of cold tolerance of tomato.Transcript factor ETHYLENE RESPONSE FACTOR(ERF)is induced by multiple hormonal signals and stress conditions and has important functions in plant adaptation to biotic and abiotic stresses such as pathogen,mechanical damage,extreme temperature,ultraviolet radiation,drought,and high salinity.However,the role of tomato ERFs subfamily in cold tolerance hasn’t been studied.In this study,the role of tomato ERF15 in the regulation of low temperature resistance was studied using genetic and molecular biology methods.We showed that ERF15 positively regulated cold resistance by regulating CBF1,WRKY6 and SAG21 like,three genes related to cold resistance pathway.ERF15 was also involved in ABA-mediated low temperature resistance.The main results are as follows:1.The role of ERF15 in low temperature resistance was clarified.Low temperature significantly induced the expression of ERF15,and the expression of ERF15 reached the highest level at 12 h after low-temperature treatment.Compared with the wild type,erf15 #1 and erf15 #3 plants showed decreased low temperature resistance with severe wilting and leaf damage phenotype,with decreased Fv/Fm value,and increased relative electrolyte leakage(REL)after 7 days cold treatment.Therefore,tomato ERF15 positively regulates the low temperature resistance.2.The molecular mechanism of tomato ERF15 regulating low temperature resistance was clarified.According to the reported targeting site(CCGNCC)of ERF15,we found three cold related-genes CBF1,WRKY6 and SAG21 like as the potential target genes of ERF15.After low temperature stress,the expression of these three genes was highly induced,and the expression pattern of these genes was lagged behind the expression of ERF15.Also,the expression of CBF1,WRKY6 and SAG21 like was significantly lower in erf15 #1 and erf15 #3 plants,than those of the wild type under low temperature.We further confirmed the role of CBF1,WRKY6 and SAG21 like in cold tolerance via virus-induced gene silencing.Dual luciferase complementation assay demonstrated that ERF15 could activate the expression of CBF1,WRKY6 and SAG21 like under low temperature.Y1 H analysis confirmed that ERF15 could bind to the promoters of these three target genes.In conclusion,ERF15 directly binds to the promoters of CBF1,WRKY6 and SAG21 like and activates their expression to regulate low temperature resistance of tomato.3.The role of ERF15 in ABA-mediated low temperature resistance was elucidated.It was found that the ABA content of erf15#1 and erf15#3 mutant lines was not significantly different from that of the wild type after 12 h of low temperature treatment.However,the lack of endogenous ABA decreased ERF15 expression,while exogenous ABA increased ERF15 expression under low temperature stress.Exogenous application of ABA could enhance low temperature resistance in wild-type plants but not in erf15#1and erf15#3 mutant plants.These results suggested that ERF15 functions downstream of ABA in regulating tomato low temperature resistance.In addition,under low temperature stress,endogenous ABA deficiency reduced the expression of CBF1,WRKY6,and SAG21 like,while exogenous ABA application increased the expression of CBF1,WRKY6 and SAG21 like in wild-type plants but not in erf15#1 and erf15#3 plants.These results suggested that ERF15 functions downstream of ABA pathway to trigger the expression of CBF1,WRKY6 and SAG21 like and low temperature resistance in tomato. |
