| In recent years,extreme weather occurs frequently,especially cold stress.In terms of jujubes,most studies are focused on physiological and biochemical,little is known about the molecular mechanisms of freezing tolerance.In this study,DEGs were analyzed through transcriptome sequencing between ‘Dongzao’ and ‘Jinsixiaozao’ under freezing stress.And the members associated with freezing stress were explored at the genomic level,the functional of low temperature response candidate genes ZjDREB1 and ZjSOD1 were identified.The main results are as follows:(1)Comprehensive analysis of cold responsive genes via comparative transcriptome analysis using two Chinese jujube cultivars(‘Dongzao’ and ‘Jinsixiaozao’)with contrasting freezing tolerance.And 854 different expression genes were simultaneously in two cultivars.Further,GO and KEGG analysis of differential genes enriched important functions and metabolic pathways such as cellular metabolic processes,stimulation responses,and transcriptional activities.In addition,nine DEGs participated in the pathway of Ca2+ signal,thirty-two DEGs were identified to take part in sucrose metabolism.(2)Bioinformatics analysis identified 56 ZjWRKY genes,118 ZjAP2/ERF,55 ZjNAC genes,26 Zjb ZIP genes and 7 ZjSOD genes in ‘Dongzao’.The differentially expression in different tissues and different degree cold stress of each family member were analyzed,the results showed that most genes can respond to low temperature stress and show different expression patterns.Among them,ZjDREB1 and ZjSOD1 changed significantly under cold stress,which may be closely related to the freezing stress.(3)The full-length sequence of gene ZjDREB1 was 768 bp,which has a high expression level in ‘Dongzao’ leaves.Under cold stress treatment,the transgenic plants of Arabidopsis thaliana had better growth potential,and the electrolytic leakage was significantly lower than wild type.The conductivity and MDA of transgenic jujube were significantly reduced after cold treatment,however,the electrolytic leakage and MDA content of RNAi lines were not significantly different from wild type.(4)The full-length sequence of ZjSOD1 gene was 660 bp,and the expression of ZjSOD1 gene was significant higher in fruits and flowers,especially 150 days after flower.Overexpression of ZjDREB1 increased the survival rate of Arabidopsis thaliana,but the electrolytic leakage and MDA content of jujube after overexpressing ZjSOD1 were not significantly different relative to control.(5)RNA-Seq was performed using wild type and overexpressed lines after freezing treatment.The results showed that the number of DEGs enriched in plant hormone signaling pathway,starch and sucrose synthesis pathway,which suggesting that ZjDREB1 and ZjSOD1 may be may be related to these pathways in response to freezing stress.In summary,this study provides the response genes during the freezing stress of jujube by high-throughput sequencing,bioinformatics analysis and molecular biology.We also revealed the role of ZjDREB1 and ZjSOD1 in improving the freezing tolerance of jujube.These results lay the foundation for the further investigation network regulation of jujube under freezing stress. |
