Abstract

By sucking the phloem sap and vectoring phytopathogenic viruses, aphids are a worldwide threat to crop yields. Pectic homogalacturonan (HG) has been described as a defensive element for plants during infections with phytopathogens. However, its role during aphid infestation remains unexplored. Using immunofluorescence assays and biochemical approaches, the HG methylesterification status and associated modifying enzymes during the early stage of Arabidopsis thaliana infestation with the green peach aphid Myzus persicae were analyzed. Additionally, the influence of PME activity on aphid settling and feeding behavior was evaluated by free choice assays and the Electrical Penetration Graph technique, respectively. Our results revealed that HG status and its modifying enzymes are significantly altered during the early stage of the plant-aphid interaction. Aphid infestation induced a significant increase in total PME activity and methanol emissions, concomitant with a decrease in the degree of methylesterification of HG. Conversely, inhibition of PME activity led to a significant decrease in the settling and feeding preference of aphids. Furthermore, we demonstrate for the first time the defensive role of a PME inhibitor (AtPMEI13) during aphid infestation, since pmei13 mutants are significantly more susceptible to M. persicae in terms of settling preference, phloem access, and phloem sap drainage.