Abstract:In this study, we used bioinformatics approaches to retrieve 11 family genes encoding for PAO from tomato genome, which were further named as SlPAO111 grouped into three subfamilies (Ⅰ, Ⅱ, and Ⅲ). In addition, gene structure analysis, protein secondary structure prediction and subcellular location prediction results are demonstrated that SlPAOs gene family have distinct subfamily categorization characteristics. Sequence and phylogenetic analysis suggest that SlPAO18 belonging to subfamily Ⅰ and Ⅱ are typical PAO genes. Proteins encoded by SlPAO911 belonging to subfamily Ⅲ contain specific SWIRM domain, SlPAO911 are characterized as histone lysinespecific demethylases, but not real PAO. Then, we used qRTPCR to analyze the relative expression level of 8 typical SlPAOs (SlPAO18) in different tissues (dry seeds, fresh leaf, cotyledon, stem, root) of tomato plant, the results showed that the expression levels of SlPAO18 in different tissues were significantly different. It is speculated that there may be a certain correlation between the diversity of expression and functional diversity of the SlPAOs gene family.