Abstract:

Serine hydroxymethyltransferase(SHMT),as an important enzyme involved in basic metabolism,plays an important role in plant cell metabolism,photorespiration and defense activities.To understand the bioinformatics function of the SHMT gene family in watermelon,explore its gene expression characteristics under abiotic stress,and provide a basis for the functional development of watermelon SHMT and the breeding of watermelon stress-resistance genes.Bioinformatics methods were used to identify SHMT family,and RT-qPCR was used to analyze the expression patterns of ClSHMTs in different tissues and abiotic stresses.The results showed that 8 ClSHMTs gene family members were identified in the whole genome of watermelon,which were unevenly distributed on 6 chromosomes and named ClSHMT1—ClSHMT8 in turn.There were some differences in the physical and chemical properties of each gene family member,such as the number of amino acids,molecular weight,isoelectric point.The protein contained 471—585 amino acids,with molecular weight of 51.87—65.00 ku and isoelectric point of 6.57—8.52,all of which were hydrophilic proteins.The subcellular localization prediction was mainly distributed on mitochondria.Gene structure and protein conserved motifs analysis showed that the ClSHMTs structure consisted of 4—15 exons and 3—14 introns,and all ClSHMTs contained conserved SHMT domains.Furtherly,phylogenetic analysis with 6 species such as cucumber and wheat showed that 50 SHMTs were divided into 3 sub-families,Group Ⅰ—Ⅲ.Promoter of ClSHMTs contained cis-acting elements related to light response,plant hormone response and stress response.The expression pattern analysis showed that 6 ClSHMTs were expressed in different tissues of watermelon,and the expression levels of ClSHMT1,ClSHMT4,ClSHMT5,ClSHMT8 in leaves were significantly higher than those in other tissues.Under low temperature,drought and salt stress,the expression abundance of ClSHMTs varies,but the expression was mainly up-regulated.In conclusion,this study systematically analyzed the SHMT gene family in watermelon,and will provide a reference for the further study of the biological functions of ClSHMTs.

Key words: Watermelon, SHMT gene family, Genome-wide identification, Abiotic stress, Expression analysis