S-adenosylmethionine (SAM) is widely involved in variety of biosynthetic processes. It participates in the methionine (Met) metabolic pathway. SAM synthetase (EC 2.5.1.6) is the main enzyme that creates SAM from Met and adenosine triphosphate. SAMS genes are highly conserved in different species. We have isolated SAMS genes from red algae, Pyropia tenera. It has been reported that SAMS genes can confer abiotic stress-related response and growth of plant organs in other species. To elucidate the function of PtSAMS gene in evolutionary perspective, we analyzed SAMS gene using bioinformatics tools and plant transformation of Arabidopsis.