Characterization of MPK family members in the genus Citrus (Rutaceae) and analysis of the function of AbMPK13 in the response to citrus canker in Atalantia buxifolia

Citrus bacterial canker has deleterious effects on global citrus production. The mitogen-activated protein kinase (MAPK) signaling cascade regulates plant defense against pathogen infection. Here, we identified 11 MAPKs in Atalantia buxifolia, a wild citrus species with high stress tolerance. Phylogenetic and gene structure analysis of the identified MAP kinases ( MPKs ) was conducted, and conserved motifs were identified. MPK expression was altered in Xanthomonas citri subsp. citri (Xcc)-resistant Atalantia buxifolia and Xcc-sensitive sweet orange after Xcc infection. AbMPK13 expression was significantly up-regulated after Xcc infection. AbMPK13 was localized to the cytoplasm, and its overexpression enhanced the resistance of sweet orange to Xcc and activated the salicylic acid (SA) signaling pathway. These findings clarify the role of MPKs in the citrus canker resistance of A . buxifolia.