Arabidopsis Is Required for Controlling Aphid Feeding from the Phloem.

The actin cytoskeleton network has an important role in plant cell growth, division, and stress response. Actin-depolymerizing factors (ADFs) are a group of actin-binding proteins that contribute to reorganization of the actin network. Here, we show that the Arabidopsis () is required in the phloem for controlling infestation by Sülzer, commonly known as the green peach aphid (GPA), which is an important phloem sap-consuming pest of more than fifty plant families. In agreement with a role for the actin-depolymerizing function of ADF3 in defense against the GPA, we show that resistance in was restored by overexpression of the related ADF4 and the actin cytoskeleton destabilizers, cytochalasin D and latrunculin B. Electrical monitoring of the GPA feeding behavior indicates that the GPA stylets found sieve elements faster when feeding on the mutant compared to the wild-type plant. In addition, once they found the sieve elements, the GPA fed for a more prolonged period from sieve elements of compared to the wild-type plant. The longer feeding period correlated with an increase in fecundity and population size of the GPA and a parallel reduction in callose deposition in the mutant. The -conferred susceptibility to GPA was overcome by expression of the coding sequence from the phloem-specific promoter, thus confirming the importance of function in the phloem. We further demonstrate that the -dependent defense mechanism is linked to the transcriptional up-regulation of , which is an important regulator of defenses against the GPA.