The LC-MS/MS data suggest that treatment of plant tissue homogenate with sodium sulfite disrupts the host-virus interactome that is required for virus transmission by aphids. Here, the host-virus interactome is defined as the complement of host plant proteins binding directly to or in complex with the purified virus. The host proteins may play a direct role in virus uptake, maintaining virion stability, or help to provide enzymatic or cofactor activity during initial steps of entry into aphid cells. We hypothesized that if host plant proteins were involved in transmission, either via direct interactions with virions or by another indirect mechanism, we should be able to detect evidence of these proteins accumulating to higher levels in aphids that have fed on infected plants compared to aphids that have fed on healthy plants. A targeted proteomics approach called selective reaction monitoring (SRM) mass spectrometry [32, 33, 34, 35] was used to detect peptides derived from virus-interacting plant proteins in aphid protein homogenates. SRM detects and quantifies selected tryptic peptides within a total protein extract that are unique to the proteins of interest by monitoring specific intact tryptic peptides ions and their collisionally-induced dissociation (CID) fragments (ions derived from fragments of the tryptic peptides) based on in silico predictions of their mass:charge ratios. In contrast to the discovery approach that enabled us to ask ''What host proteins are in the different virus preparations?'' (Table 4) , SRM enables us to ask the hypothesis-driven question, ''Are virus-interacting plant proteins A, B, and C, present in our aphid protein sample?''.