Seauences Analysis Of SlOMT Genes And Functional Characterization Of Melatonin Synthesis-related Gene SlCOMT1 In Tomato

In plants,methylation is a common enzymatic reaction and a variety of secondary metabolites are methylated by oxygen methyltransferase(O-methyltransferase,OMT)which also can regulate melatonin biosynthesis.OMTs are involved in regulation of plant development and can enhance the plant resistance to biotic and abiotic stress.OMT proteins are divided into two types,i.e.CCoAOMT and COMT.COMT is a key enzyme in melatonin synthesis pathway.Melatonin can be used as a growth regulator in plants and can enhance the resistance of plants to external stress.In this study,bioinformation of OMT genes were analyzed in tomato,and a melatonin synthesis-related gene SICOMT1 was cloned from tomato.Subsequently.SICOMT1 overexpression transgenic tomatoes were obtained to identify its function.Though the above study,it is useful for revealing the regulation mechanism of melatonin in the growth and development in tomato.The main findings were as follows:1.SIOMT genes encoded two tyes of O-methyltransferase,i.e.COMT-type and CCoAOMT-type.In the tomato genome,18 SIOMT genes were identified and were named SIOMT1-18,respectively.These genes are distributed on 8 chromosomes,and the gene length is between 726 bp and 1338 bp.Additionally,they encodes two types enzymes in tomato,i.e.,SIOMT 1-9 proteins belong to the COMT-type of O-methyltransferase,and SlOMT 10-18 proteins belong to the CCoAOMT-type of O-methvltransferase.2.SIOMT genes were constitutive expressed in different organs in tomato.SIOMT genes were expressed in tomato buds,roots,stems,leaves,flowers and fruits to varying degrees.The genes with high expression in buds were SIOMT4,SlOMT2,SIOMT13,SlOMT14 and SlOMT15;The genes with high expression in flowers were SIOMT4,SIOMT9,SIOMT13,SIOMT14 and SIOMT15:The genes with high expression in root were SIOMT2,SIOMT10,SIOMT11,SIOMT12,SIOMT13 and SIOMT14;Furthermore,and the genes with high expression in fruits were SIOMT6,SlOMT9 and SIOMT11.3.SICOMT1 protein has the highest homology with AtCOMT in Arabidopsis and localizes in the cytoplasm.The SICOMT1 gene was cloned by homologous alignment in tomato,and its protein has the highest homology with AtCOMT in Arabidopsis.The SICOMT1 gene is 1023 bp in length and encodes 341 aa with a protein size of 37 kD.SICOMT1 gene was localized in the cytoplasm and displayed the highest expression in roots.4.SICOMT1 transgenic tomatoes enhanced the resistance to salt stress.In this study.SlCOMT1 overexpression transgenic tomatoes were obtained to identify its function in tomato.Melatonin content in SICOMT1 overexpression transsenic tomato plants was significantly higher than that in wild-type plants.The transgenic plants displayed increased proline levels and decreased hydrogen peroxide and superoxide levels,and the transgenic tomatoes tolerated salt stress better than the wild-type tomatoes.The results indicated that SICOMT1 was closely related to melatonin production and functioned in the improvement of plant resistance to abiotic stress.