Genome-Wide Identification And Expression Profiles Analysis Of Mitogen-Activated Protein Kinase Family Genes In Solanum Lycopersicum

Plant growth is severely affected by environmental stresses, which makes stress resistance research more important. Recently, more and more experimental proofs and datas indicated that MAPK(mitogen-activated protein kinase) has very important effects on plant growth and development, as well as stress resistance. Up to date, a number of MAPK genes have been isolated from different plants, and considerable progresses have been made in understanding of plant MAPK genes. Current research on tomato(Solanum lycopersicum L.) MAPK genes is relatively less. The recently completed Genome Sequencing Project for tomato provides an opportunity to dissect the information of MAPK gene family. In this study, we identified13MAPK genes in the tomato genome. The classification, protein properties, gene structure, chromosomal distribution, evolutionary relationship and expression pattern in different tissues of tomato MAPK genes have been analyzed. To analyze the expression pattern of SIMAPKs in various floral developmental stages, flower buds were collected at five stages of floral development. Based on the analysis, we focused on the function of SIMAPK4, SIMAPK7, SlMAPK12and SIMAPK16under different stress treatments. The main results are as follows:(1) The full-length cDNA sequences of all13newly identified SIMAPKs were isolated through homogous cloning and RACE. The open reading frame (ORF) length ranged from1113bp to1866bp, encoding polypeptides of370aa to621aa. All the deduced protein contain11subdomains of MAPK and the phosphorylation-activation motif, T-X-Y. As we know, SlMAPK1, SIMAPK2and SIMAPK3have already been identified in tomato, so these genes were named as SIMAPK4-16. All the16SIMAPKs were divided into four groups, group A, B, C and D. There are various cis-acting elements which might play essential roles in growth and development, and also in mediating stress responses.(2) The expression patterns of MAPK genes in different tomato tissue and floral developmental stages were analysed by RT-PCR and qRT-PCR. The results indicated that transcripts of most MAPK genes could be detected in leaf, stem, flower and fruit using RT-PCR. The quantitative analysis (qRT-PCR) also demonstrated that most MAPK genes had higher expression levels in stamen or petal than in other organs. During the developmental stages of tomato flower, different MAPK members in tomato exhibited different expression patterns. The expression levels of SIMAPK9and SIMAPK10significantly decreased at the early flower bud stage, while SIMAPK8, SIMAPK14and SIMAP16markedly decreased at the late flowering stage. SIMAPK3, SIMAPK4and SIMAPK13transcript levels significantly increased until flower Ⅱ stage and then markedly decreased. The expression levels of SIMAPK1, SIMAPK2, SIMAPK5and SIMAPK12seemed to have no obvious changes during tomato flower development. These results indicated that some MAPK genes may have very important effects on flower development. (3) The expression patterns of SIMAPKs genes under high-temperature, salt and wound stress were analysed by qRT-PCR. We found that most of SIMAPK genes exhibited differential expression patterns in response to high-temperature stress (45±1℃) treatment. Most SIMAPKs were up-regulated upon the exposure to the heat stress. The expression of SIMAPKI, SIMAPK3and SIMAPK8gradually increased in response to heat stress, while SIMAPK2, SIMAPK4, SIMAPKS, SIMAPK6, SIMAPK7, SIMAPK9, SIMAPK12and SIMAPKI6increased at the early stage, then decreased. The mRNA transcript changes of SIMAPKIO, SIMAPK11, SIMAPK13, SIMAPK14and SIMAPK15were not significant. We focused on the expression patterns of SlMAPK4、SIMAPK7、SIMAPK12and SIMAPK16upon other stress treatments. After salt stress, SIMAPKI2and SIMAPK16increased at the early stage then decreased. The expression levels of these four genes increased at the early stage then decreased in mechanical injury stress.(4) Expression patterns of SIMAPK4, SIMAPK7、 SIMAPK12and SIMAPK16were analysed in tomato upon SA, ABA, JA, ACC and H2O2treatments. SIMAPK4, SIMAPK7, SIMAPK16were significantly up-regulated in response to SA. After the treatment of ABA, SIMAPK16had significant changes. SIMAPK12was significantly down-regulated in response to JA. The transcript levels of SlMAPK4,SlMAPK7,SlMAPK12and SIMAPK16showed no significantly changes after ACC treatment. The expression levels of SIMAPK7and SIMAPKI6increased upon H2O2treatment.