D3275: Overexpression of caffeoyl coenzyme-A O-methyltransferase provides enhanced sorghum resistance to sugarcane aphids

Abstract

Sorghum (Sorghum bicolor) is one of the world’s most important monocot crops grown for grain and bioenergy. However, sorghum production in the United States has been negatively impacted by the attack of a piercing-sucking insect pest, sugarcane aphid (SCA; Melanaphis sacchari). In plants, including sorghum, monolignol biosynthesis pathway is a major target for altering lignin content and composition. Caffeoyl-coenzyme A O-methyltransferase (CCoAOMT)is an enzyme involved in monolignol biosynthesis. It catalyzes the methylation of the 3-hydroxyl group of caffeoyl-CoA to generate feruloyl-CoA, which is required to synthesize lignin subunits. In our study, we used the sorghum reference line, RTx430 (wild-type), and two CCoAOMT gene overexpression lines, CCoAOMT9a and CCoAOMT28b, to assess the role of the CCoAOMT gene in sorghum resistance to SCA. Using the choice and no-choice assays, we have identified that the overexpression of CCoAOMT provided enhanced resistance to SCA compared to RTx430 plants. The Electrical Penetration Graph (EPG) analysis unveiled that the SCA spent significantly less time in the sieve element phase of CCoAOMT overexpression plants compared to RTx430 plants. Our study collectively demonstrates that the overexpression of the CCoAOMT gene provides enhanced resistance to SCA and deters the aphid from prolonged feeding from the sieve elements compared to the RTx430 plants. Based on our results, we propose that CCoAOMT or CCoAOMT-dependent metabolites contribute to enhanced resistance to SCA.