ABSTRACT
O-methylation of flavonoids is an important modification reaction that occurs in plants. O-methylation contributes to the structural diversity of flavonoids, which have several biological and pharmacological functions. In this study, an O-methyltransferase gene (CrOMT2) was isolated from the fruit peel of Citrus reticulata, which encoding a multifunctional O-methyltransferase and could effectively catalyze the methylation of 3'-, 5'-, and 7-OH of flavonoids with vicinal hydroxyl substitutions. Substrate preference assays indicated that this recombinant enzyme favored polymethoxylated flavones (PMF)-type substrates in vitro, thereby providing biochemical evidence for the potential role of the enzyme in plants. Additionally, the cytotoxicity of the methylated products from the enzymatic catalytic reaction was evaluated in vitro using human gastric cell lines SGC-7901 and BGC-823. The results showed that the in vitro cytotoxicity of the flavonoids with the unsaturated C2-C3 bond was increased after being methylated at position 3'. These combined results provide biochemical insight regarding CrOMT2 in vitro and indicate the in vitro cytotoxicity of the products methylated by its catalytic reaction.
Subject(s)
Citrus/enzymology , Cytotoxins/pharmacology , Flavones/pharmacology , Plant Proteins/chemistry , Protein O-Methyltransferase/chemistry , Cell Line, Tumor , Cell Survival/drug effects , Citrus/chemistry , Cytotoxins/chemistry , Cytotoxins/isolation & purification , Epithelial Cells/drug effects , Epithelial Cells/pathology , Flavones/chemistry , Flavones/isolation & purification , Fruit/chemistry , Fruit/enzymology , Humans , Inhibitory Concentration 50 , Methylation , Plant Proteins/isolation & purification , Protein O-Methyltransferase/isolation & purification , Substrate SpecificityABSTRACT
BACKGROUND: Brown planthopper (BPH) is the most destructive insect in rice production. Breeding of resistant cultivars is the most cost-effective and environment-friendly strategy for BPH management; however, resistant cultivars are currently hampered by the rapid breakdown of BPH resistance. Thus, there is an urgent need to use more effective BPH resistance genes or pyramiding different resistance genes to develop more durable resistant rice cultivars. RESULTS: Here a dominant BPH resistance gene Bph27(t) were introgressed into a susceptible commercial japonica variety Ningjing3 (NJ3) and indica variety 93-11 using marker-assisted selection (MAS), respectively. Further, Bph27(t) and a durable BPH resistance gene Bph3 was pyramided by intercrossing single-gene introgressed lines through MAS. The introgression of BPH resistance genes significantly improved the BPH resistance and reduced the yield loss caused by BPH. CONCLUSION: The development of single and two genes pyramided lines in this study provides innovative resources for molecular breeding of durable BPH-resistant rice cultivars and BPH management through resistant cultivars.