Louis_2010_Plant.J_64_800

The green peach aphid (GPA) (Myzus persicae Sulzer) is an important sap-sucking pest of a large variety of plants, including Arabidopsis thaliana. Arabidopsis utilizes a combination of defenses that deter insects from settling on the plant, limit insect feeding and curtail insect reproduction. We demonstrate that the previously uncharacterized Arabidopsis MPL1 (MYZUS PERSICAE-INDUCED LIPASE1) gene has an important role in defense against the GPA. MPL1 expression was rapidly induced to high level in GPA-infested plants. Furthermore, the GPA population was larger on the mpl1 mutant than the wild-type (WT) plant. In contrast, constitutive over-expression of MPL1 from the Cauliflower mosaic virus 35S gene promoter curtailed the size of the GPA population. Insect settling and feeding behavior were unaffected on the mpl1 mutant. However, compared with the phloem-sap enriched petiole exudate from the WT plant, mpl1 petiole exudate was deficient in an activity that restricts insect reproduction on a synthetic diet. Furthermore, MPL1 was required for the heightened accumulation of an antibiotic activity in petiole exudate of the Arabidopsis ssi2 mutant, which exhibits enhanced resistance to GPA. These results indicate that MPL1 has an essential function in antibiosis against GPA. The MPL1 protein exhibits homology to lipases and recombinant MPL1 has lipase activity, thus suggesting that a MPL1-dependent lipid, or a product thereof, has an important role in antibiosis against GPA.