Genome-Wide Analysis of the Amino Acid Auxin Permease (AAAP) Gene Family and Identification of an AAAP Gene Associated with the Growth and Reproduction of the Brown Planthopper, Nilaparvata lugens (Stål)

SIMPLE SUMMARY: Amino acids are one of the essential nutrients in organisms and play unique roles in multiple life activities. However, most insects cannot synthesize several amino acids and must acquire them from dietary sources. Diffusion of amino acids into and out of insect cells is heavily dependent on amino acid transporters. The amino acid auxin permease represents one of the most important amino acid transporter gene families in insects. However, amino acid transporters in most insects are not well understood. Here, we performed genome-wide identification of the amino acid auxin permeases in the brown planthopper (BPH), Nilaparvata lugens, a devastating pest that feeds on the phloem sap of rice plants. The molecular traits and evolutionary patterns of these putative amino acid auxin permeases in BPH were analyzed. An amino acid auxin permease which was predicted to regulate BPH nymphal growth and female fecundity was identified and functionally validated through RNA interference and bioassay experiments. Our results provide a basis for further functional research on the amino acid auxin permeases in BPH and suggest new ideas for the management of this pest. ABSTRACT: Amino acids play a vital role in several biological processes in organisms and are mainly acquired through diet by most insects. The amino acid auxin permease (AAAP) transporter family is an important amino acid transporter gene family in insects for the transportation of amino acids into and out of cells across the plasma membrane. Here, we identified 21 putative AAAP family members in the genome of the brown planthopper (BPH), Nilaparvata lugens, a devastating pest that feeds only on the phloem sap of rice plants. Molecular characteristic analysis indicated large variations in protein features and amino acid sequences among the predicted AAAP family members in BPH. Phylogenetic analysis clustered these AAAP transporters into three subgroups, with the members in the same group sharing a similar pattern of conserved motif distribution. Through ortholog gene recognition and spatiotemporal gene expression analysis, the AAAP gene NlAAAP07, which was predicted to regulate BPH larval growth and female fecundity, was identified. RNA interference (RNAi)-mediated suppression of NlAAAP07 significantly postponed the duration of 3rd instar nymphs developing into adults from 7.4 days to 9.0 days, and decreased the oviposition amount and egg hatching rate of females by 30.7% and 11.0%, respectively. Our results provide a foundation for further functional analysis of AAAP transporters in BPH.