The cotton aphid, Aphis gossypii, is an important agricultural pest that can feed on a broad range of host plants. Its feeding not only injures crop plants, but also serves as a route for the transmission of circulative plant viruses including cotton leafroll dwarf virus, of which A. gossypii is the only known vector. The aphid salivary glands are involved in virus transmission and play a pivotal role in plant colonization by producing secretory proteins that are injected into host tissues to suppress plant defenses, detoxify phytochemicals, and digest plant macromolecules. To understand how A. gossypii transmits plant viruses and colonizes its hosts, tissue-specific RNA-Seq analysis was performed on the salivary glands collected from 200 dissected cotton-fed alates of a greenhouse population. A de novo transcriptome of 108,673 transcripts was generated, and 952 genes were predicted to encode secretory salivary gland proteins (SSGPs) following a developed in silico pipeline. Differential gene expression analysis indicated that, among these 952 genes, 351 were highly expressed in heads where salivary glands were included, compared to abdomens, suggesting their specific roles in plant feeding. Interestingly, several putative SSGPs in A. gossypii showed sequence similarity to some characterized host-manipulating effector proteins previously identified in other aphid species, including C002, Mp1, Mp10, ACE1, and those involved in plant glucose metabolism to reduce host defense responses. Although the functions of these putative salivary gland proteins in A. gossypii are yet to be determined, this study provided valuable insights into the molecular interactions between A. gossypii and cotton.
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