Loss of flavonol 3-O-glucosyltransferase activity confers soybean resistance to leaf-chewing insects

Caterpillars and beetles are among the most economically damaging defoliating insects, and their economic damage is predicted to increase in the coming decades. Hence the use of genetically derived resistance to supplement other pest control strategies is warranted. In soybean (Glycine max (L.) Merr.), a major determinant for resistance is the quantitative trait locus, QTL-M. Glyma07g14530, the gene underlying QTL-M, encodes a feeding-inducible flavonol 3-O-glycosyltransferase (F3GlcT or UGT78D2) that glucosylates kaempferol, as well as quercetin, myricetin, and isorhamnetin. The resistant allele has a premature stop codon in it, thus preventing the glucosylation and sequestration of flavonols in the vacuole, leading to a concomitant accumulation of proanthocyanidins and manifestation of resistance. Expressing the dominant (susceptible) allele in resistant plants restores susceptibility and silencing the susceptible allele results in resistance. The discovery and characterization of GmF3GlcT helps clarify the role of flavonoids in resistance to leaf-chewing insects and facilitates the development of insect-resistant cultivars that ultimately can lower production costs and reduce insecticide applications. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/679769v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@10e2e77org.highwire.dtl.DTLVardef@ca905org.highwire.dtl.DTLVardef@12cb46corg.highwire.dtl.DTLVardef@1f9328b_HPS_FORMAT_FIGEXP M_FIG C_FIG The loss of flavonol 3-O-glucosyltransferase in soybean reduces feeding damage from defoliating insects and is accompanied by a concomitant increase in proanthocyanidins (red arrowhead). SignificanceUnraveling the biochemical and genetic basis of soybean resistance to leaf-chewing insects facilitates the development of new, naturally insect resistant varieties. Such varieties contribute to on-farm profitability and reduced concerns over pesticide residues in the field.