“…On the route to the phloem, the stylets navigate between epidermal and mesophyll cells, occasionally penetrating these cells during a process known as the pathway feeding phase (Tjallingii, 1985;Tjallingii and Esch, 1993). The ability of an aphid to feed successfully on a plant appears to be partly determined during these penetrations, as the pathway phase still occurs with aphid species unable to establish long-term feeding (Chen et al, 1997;Sauge et al, 1998;Jaouannet et al, 2015;Nam and Hardie, 2012). Furthermore, as with microbial pathogens, aphids are detected through a BAK1-dependent mechanism, although the PRRs involved have remained elusive, with FLAGELLIN-SENSITIVE2 (FLS2), EF-TU RECEPTOR (EFR), CHITIN ELICITOR RECEPTOR KINASE1 (CERK1), PEP1 RECEPTOR1 (PEPR1), and PEPR2 not appearing to play a role (Prince et al, 2014;Chaudhary et al, 2014).…”