Abstract:Mitogen activated protein kinase (MAPK) plays important roles in regulating plant growth and developmental processes as well as in response to various stresses. In order to learn the structure and the function of MAPKs, a novel tomato MAPK gene, named as SlMAPK9-2, was cloned and identified using PCR methods and bioinformatic analysis. BLASTP analysis on the NCBI database and MEME showed that the SlMAPK9-2 contained the conserved characteristic domains and motifs of the MAPK gene family further phylogenetic analysis indicated that SlMAPK9-2 was belonged to the D subgroup of MAPK and it was clustered at the same branch with StMAPK9 and NtMAPK9 in the phylogenetic tree. Using the Plant Gene Duplication Database, segmental duplications between SlMAPK9-2 and SlMAPK16, as well as between SlMAPK9-2 and PmMAPK9 were identified. Meanwhile, the Ka/Ks ratios were less than 1, suggesting that the duplicated gene pairs experienced purifying selection after gene duplications. QRT-PCR analysis showed that SlMAPK9-2 was expressed in all tested tomato tissues and highly expressed in opened flowers. Additionally, it was markedly upregulated by heat and salinity stresses, as well as abscisic acid and slicylic acid treatments. Promotor structure predicted by PLACE and PlantCARE also exhibits there are numerous cis-acting regulatory elements involved in the response to pathogen infection, hormones, heat, and dehydration stresses. These results suggest that SlMAPK9-2 may play significant roles in regulating abiotic stress responses and mediating phytohormone signaling in tomato. This research laid a foundation for further illuminating the functional and working mechanism of SlMAPK9-2 in tomato.