Green peach aphid (Myzus persicae (Sülzer))–Arabidopsis thaliana interaction

Aphids are important pests of plants that cause substantial loss in plant productivity. In addition, aphids also vector plant viruses. In contrast to the chewing herbivorous insects, aphids utilize their long slender stylet to feed continuously from the sieve element of plants for extended periods of time. We have utilized the interaction between the model plant Arabidopsis thaliana and the green peach aphid (GPA; Myzus persicae Sülzer) to study plant defenses against aphids. Previously, we demonstrated that the Arabidopsis PHYTOALEXIN DEFICIENT4 (PAD4) gene, which exhibits homology to acyl hydrolases, is an important modulator of antixenosis (feeding deterrence) and antibiosis (affect aphid fecundity) against GPA (Pegadaraju et al. 2005, 2007). PAD4-dependent resistance against GPA was accompanied by elevated expression of SENESCENCE ASSOCIATED GENES (SAG). The PAD4 protein contains conserved Ser, Asp and His residues that form the catalytic triad of many α/β fold acyl hydrolases. Arabidopsis plants expressing mutant versions of PAD4 [PAD4(S118A) and PAD4(D178A)] supported higher numbers of GPA as compared to wild type (WT) plants in no-choice tests. However, PAD4(S118A) and PAD4(D178A) mutations did not impact antixenosis activity in choice tests, PAD4-modulated expression of SAG and cell death in GPA infested plants, suggesting that the antixenosis and antibiosis activity of PAD4 are determined by separate regions of PAD4. In the future, the electrical penetration graph (EPG) technique will be utilized to study the feeding behavior of GPA on mutant versions of PAD4.