[Isolation and functional characterization of (iso)eugenol O-methyltransferase (IEMT) gene in Asarum sieboldii].

Methyleugenol is one of the main active constituents in the volatile oil of the traditional Chinese medicine Asari Radix et Rhizoma. It possesses various pharmacological effects such as analgesic, anesthetic, and anti-inflammatory properties. In biosynthesis, the initial precursor phenylalanine is finally converted into methyleugenol through a series of intermediate compounds including coniferyl acid, courmaryl acid, caffeic acid, ferulic acid/ferulic-CoA, coniferyl aldehyde, conferyl alcohol, cnfiferyl acetate, and eugenol/isoeugenol, which are produced through catalysis of a large number of enzymes. Eugenol O-methyltransferase(EOMT) is one of the key enzymes in the biosynthesis pathway, capable of methylating eugenol on the para-site hydroxyl group of the benzene ring, thereby generating methyleugenol. Here, an(iso)eugenol O-methyltransferase(IEMT) gene was cloned for the first time from Asarum siebo-ldii, holding an open reading frame that consisted of 1 113 bp and encoded a protein containing 370 amino acid residues. Bioinformatics analysis results showed that this protein was equipped with the characteristic structural domains of methyltransferases such as S-adenosylmethionine(SAM) binding sites and dimerization domains. The prokaryotic expression recombinant plasmid pET28a(+)-AsIEMT was constructed, and the candidate protein was induced and purified. In vitro enzyme assays confirmed that AsIEMT had dual functions. The enzyme could catalyze the production either of methyleugenol from eugenol or of methylisoeugenol from isoeugenol, although the latter was more prevalent. When isoeugenol was used as the substrate, the kinetics parameters K_m and V_(max) of catalytic reaction were(0.90±0.06) mmol·L~(-1) and(1.32±0.04)nmol·s~(-1)·mg~(-1), respectively. This study expanded our understandings of critical enzyme genes involved in phenylpropanoid metabolic pathways, and would facilitate the elucidation of quality formation mechanisms of the TCM Asari Radix et Rhizoma.

[Exploration of transcriptome SSR markers and its application in genetic diversity assessment of Asarum sieboldii].

To explore the genetic diversity of Asarum sieboldii this study developed SSR markers based on transcriptome sequencing results and five populations of A.sieboldii from different regions were used as samples for genetic diversity assessment using software such as GenALEx 6.5, NTSYS 2.1, and Structure 2.3.4. The results showed that 16 SSR markers with high polymorphism and good repeatability were selected from the A.sieboldii transcriptome. Primers designed based on the flanking sequences of these markers successfully amplified 56 polymorphic fragments from 150 individual samples of the five A.sieboldii populations. On average, each primer amplified 3.5 polymorphic fragments, ranging from 2 to 8. The mean values of expected heterozygosity(H_e), Shannon's diversity index(I), Nei's gene diversity index(H), and the polymorphic information content(PIC) were 0.172, 0.281, 0.429, and 0.382, respectively. The mean population differentiation coefficient(F_(ST)) was 0.588, consistent with the analysis of molecular variance(AMOVA) results, which indicated greater genetic variation among A.sieboldii populations(69%) than that within populations(31%). The percentage of polymorphic loci(PPL) ranged from highest to lowest as SNJ>LN>SY>SZ>TB. Principal coordinate analysis(PCoA) and UPGMA clustering analysis further revealed genetic clustering of A.sieboldii individuals based on their geographical distribution, consistent with the results of the structure clustering analysis. In summary, the SSR markers developed from the transcriptome effectively assessed the genetic differentiation and population structure of natural A.sieboldii populations, revealing a relatively low genetic diversity in A.sieboldii, with genetic variation primarily observed at the population level and a correlation between population differentiation and geographic distance.