| Catalase(CAT)is a highly expressed enzyme in peroxisomes,which plays an important role in the removal of Reactive Oxygen Species(ROS).CAT gene plays a variety of roles in plant resistance to adverse environment and protects plant cells from ROS toxicity.However,there is a lack of systematic identification in common tobacco(Nicotiana tabacum).In this study,we scanned the family members in the genome of common tobacco based on the identified CAT gene in the Arabidopsis thaliana genome,analyzed the physicochemical properties and subcellular localization of the family members using online website tools.Phylogenetic analysis of CAT genes in tobacco and other species was carried out by constructing evolutionary trees using MEGA X.Gene structure analysis,motif analysis and conserved domain analysis were performed to further understand CAT gene function.Transcriptome data were used to investigate the expression of CAT gene at different tissues at different times,as well as the expression pattern under cold,drought and salt stress conditions.The results of CAT gene analysis in common tobacco were as follows:(1)Seven CAT genes were identified in common tobacco and divided into three groups,class I,class II and class III.Except NtCAT7,all the other members encode 492 amino acids.The molecular weight of the protein fluctuates from 55.254-56.947 k Da,and the isoelectric point ranges from 6.50-6.95.The encoded protein is hydrophilic protein.Due to the short sequence,the physicochemical properties of NtCAT7 differ greatly from those of other family members.(2)Phylogenetic analysis of CAT genes in tobacco,Arabidopsis thaliana and other species of Solanaceae revealed that 22 CAT genes in different species could be divided into three classes.There are 6 CAT genes in class I,9 in class II and 7 in class III.The CAT gene in common tobacco is most closely related to Nicotiana plumbaginifolia,followed by other Solanaceae crops.(3)Gene structure analysis showed that NtCAT1-6 contained 6 or 7 introns.The intron distribution pattern of genes on the same branch is roughly the same;for example,the relative position of introns in NtCAT1 and NtCAT2 is highly similar.NtCAT6 contains 6 introns and lacks the 5 ’UTR region,of which the first intron is the longest,approximately 2kb.NtCAT7 has only two CDS regions and one intron.(4)Except NtCAT3 and NtCAT7,all other CAT genes contain nine motifs.Different motifs have different lengths,but the number and arrangement positions are basically the same.Motif5 is common to CAT genes.NtCAT3 lacks motif7 at the 5 ’end and NtCAT7 has only two motif5 segments at the 3’ end.The CAT gene contains two conserved domains,Catalase and Catalaserel,and NtCAT7 lacks the Catalase-rel domain.(5)Tissue specific analysis based on transcriptome data showed that NtCAT1 and NtCAT2 were mainly expressed in the shoot,and the gene expression was higher under dark conditions,such as higher expression of CAT gene in the shootapex at 0h.NtCAT3 and NtCAT4 were also concentrated in the shoot,but they were only significantly expressed from 0 to 12 hours.NtCAT5 and NtCAT6 are concentrated in the root.NtCAT7 was expressed in root,shoot and shootapex,and the gene expression was more affected by time regulation,and was more inclined to be concentrated at 0h.(6)Under cold stress conditions,NTCATs showed different expression patterns,the expression of NtCAT1-4 was down-regulated,while the expression of NtCAT5-7 was upregulated.The expression levels of NtCAT1,NtCAT5 and NtCAT7 were not sensitive to cold stress,and the change range was small.The gene expression of NtCATs was down-regulated under drought and NaCl stress conditions,especially in drought stress,which was more sensitive and the down-regulated extent was larger.Under drought stress,the expression levels of NtCAT2 and NtCAT6 were similar.Under NaCl stress,the expression levels of NtCAT1,NtCAT2 and NtCAT5 were approximately the same.In this study,CAT gene families in different species were compared and analyzed,which is helpful to understand the difference of CAT gene expression in different species.Studying the expression pattern of CAT gene in tobacco under different environmental stress can lay a foundation for tobacco stress resistance breeding. |
