Objective  The class Ⅲ peroxidase is a group of plant-specific oxidoreductases, and plays an important role in plant development and stress response. This paper presents a detailed overview of evolution and expression of olive class Ⅲ PRX gene family, aiming to provide a reference for olive molecular breeding in the future.

  Method  With some bioinformatic tools, we finished the identification of the olive class Ⅲ PRX genes, completed the analyses of phylogenetic relationship, gene mapping on the chromosomes, pairs of duplicates, motifs, gene structure, cis-acting elements and gene expression in different tissues or biotic stresses, and did a verification of RNA-seq by RT-qPCR.

  Result  (1) 106 OePRX genes were obtained, and classified into 14 groups based on the phylogeny with AtPRX and PtPRX. (2) OePRX genes were unevenly located on 23 chromosomes, and ragment replication was the main driving force for the expansion of gene family. Compared with AtPRX, OePRX had a closer relationship with PtPRX. (3) The characterization of pI, MW, motifs, gene structure, signal peptide, and expression in different tissues had the expected group-conserved patterns. The promoters of OePRX contained a variety of development and harmone elements; 38% of OePRX genes was differentially expressed in heat, drought and waterlogged stress.

  Conclusion  The differential expansion and differential expression patterns may imply flexibility in neofunctionalization of duplicated class Ⅲ peroxidase genes, which is of adaptive significance to the strong resistance of olive to a diversity of conditions, hence contributing to the importance of olive as a Mediterranean Basin staple food.