Abstract:

In plants,methionine is produced by methionine synthase（METS）using 5-methyltetrahydrofolate and homocysteine as substrates. Methionine synthase is the hub connecting methyl metabolism and one carbon metabolism. Cloning and expression analysis of METS coding sequence can provide basis information for the regulation of methionine- and folate- accumulation in maize（Zea mays）grains. The coding sequences of maize METS were cloned by RT-PCR,and its characteristics were analyzed by bioinformatics methods. The expression patterns in different tissues and during germination were detected by real-time quantitative PCR. Maize contained three homologous genes of ZmMETS1,ZmMETS2,and ZmMETS3 encoding methionine synthase,the gene length was 2 301 bp,2 298 bp and 2 298 bp,encoding 766,765 and 765 amino acids,respectively,and the protein molecular weights were all about 84.5 kD. All these three proteins contained two domains at N- and C-terminals. Each domain consisted of α helices surrounded by parallel β lamellae to form a stereoscopic structure. Phylogenetic tree analysis showed that 3 proteins were most similar to SbMETS in Sorghum bicolor. Expression analysis indicated that three ZmMETSs were expressed in all tissues of maize,and the highest transcription level was ZmMETS1. The transcription levels of three genes in ear were higher than those in other tissues. In addition,the transcription levels of ZmMETS1 and ZmMETS3 increased rapidly during germination and then decreased rapidly after germination. In conclusion,there are three constitutive expressed methionine synthase genes in maize. ZmMETS1 may play a role in ear development and germination.

Key words: Zea mays, methionine synthase, METS, germination