Figure 7.

A working model to explain the roles of AS1 and βC1 in virus–insect vector–plant interaction. AS1 is a conserved regulator for leaf polarity development and plant immune response. AS1 interacts with AS2 to down-regulate miR165/166 and up-regulate HD-ZIPIII genes, but AS1 alone acts to suppress JA responses. βC1 is encoded by the satellite DNAβ, which is associated with the helper virus, TYLCCNV. βC1 targets AS1 to manipulate leaf polarity by modulating miR165/166 and HD-ZIPIII transcripts resulting in disease symptoms. This viral protein also attenuates plant immune response by suppressing expression of several JA-responsive genes. This AS1-dependent suppression may account, in part, for the aggregation of whitefly population on TYLCCNV-infected plants.