Proteomic composition of the acrostyle: Novel approaches to identify cuticular proteins involved in virus-insect interactions.

The acrostyle is a distinct anatomical region present on the cuticle at the inner face of the common food/salivary canal at the tip of aphid maxillary stylets. This conserved structure is of particular interest as it harbors the protein receptors of at least 1 plant virus, Cauliflower mosaic virus, and presumably has other roles in plant-insect interactions. Previously we reported immunolabeling of a highly conserved motif of cuticular proteins from the CPR family (named for the presence of a Rebers and Riddiford consensus) within the acrostyle. Here we report the development of novel tools to further study the proteomic composition of this region and to identify proteins involved in insect-virus interactions. Using a series of antibodies against cuticular proteins from the RR-2 subfamily, we identified additional peptides present within the acrostyle. Our results demonstrated that the acrostyle is a complex structure containing multiple domains of cuticular proteins accessible for interaction. In addition, an array of overlapping peptides, which covers the diversity of the majority of the RR-2 subfamily, was developed as a generic tool to characterize cuticular protein/pathogen interactions. Upon probing this array with Cucumber mosaic virus particles, consensus peptide sequences from hybridizing peptides were identified. Use of these novel tools has extended our knowledge of the proteomic composition of insect maxillary stylets and identified sequences that could be involved in virus binding, thus contributing to further elucidation of the various properties and functions of the acrostyle.