Identification and Characterization of Two New S-Adenosylmethionine-Dependent Methyltransferase Encoding Genes Suggested Their Involvement in Stipe Elongation of <i>Flammulina velutipes</i>

Two new SAM-dependent methyltransferase encoding genes (<i>fvsmt1</i> and <i>fvsmt2</i>) were identified from the genome of <i>Flammulina velutipes</i>. In order to make a comprehensive characterization of both genes, we performed <i>in silico</i> analysis of both genes and used qRT-PCR to reveal their expression patterns during the development of <i>F. velutipes</i>. There are 4 and 6 exons with total length of 693 and 978 bp in <i>fvsmt2</i> and <i>fvsmt1</i>, respectively. The deduced proteins, i.e., FVSMT1 and FVSMT2 contained 325 and 230 amino acids with molecular weight 36297 and 24894 Da, respectively. Both proteins contained a SAM-dependent catalytic domain with signature motifs (I, p-I, II, and III) defining the SAM fold. SAM-dependent catalytic domain is located either in the middle or at the N-terminal of FVSMT2 and FVSMT1, respectively. Alignment and phylogenic analysis showed that FVSMT1 is a homolog to a protein–arginine omega-<i>N</i>-methyltransferase, while FVSMT2 is of cinnamoyl CoA <i>O</i>-methyltransferase type and predicted subcellular locations of these proteins are mitochondria and cytoplasm, respectively. qRT-PCR showed that <i>fvsmt1</i> and <i>fvsmt2</i> expression was regulated in different developmental stages. The maximum expression levels of <i>fvsmt1</i> and <i>fvsmt2</i> were observed in stipe elongation, while no difference was found in mycelium and pileus. These results positively demonstrate that both the methyltransferase encoding genes are involved in the stipe elongation of <i>F. velutipes</i>.