In tsetse flies, nutrients for intrauterine larval development are synthesized by the modified accessory gland (milk gland) and provided in mother’s milk during lactation. Interference with at least two milk proteins has been shown to extend larval development and reduce fecundity. The goal of this study was to perform a comprehensive characterization of tsetse milk proteins using lactation-specific transcriptome/milk proteome analyses and to define functional role(s) for the milk proteins during lactation. Differential analysis of RNA-seq data from lactating and dry (non-lactating) females revealed enrichment of transcripts coding for protein synthesis machinery, lipid metabolism and secretory proteins during lactation. Among the genes induced during lactation were those encoding the previously identified milk proteins ( milk gland proteins 1–3 , transferrin and acid sphingomyelinase 1 ) and seven new genes ( mgp4–10 ). The genes encoding mgp2–10 are organized on a 40 kb syntenic block in the tsetse genome, have similar exon-intron arrangements, and share regions of amino acid sequence similarity. Expression of mgp2–10 is female-specific and high during milk secretion. While knockdown of a single mgp failed to reduce fecundity, simultaneous knockdown of multiple variants reduced milk protein levels and lowered fecundity. The genomic localization, gene structure similarities, and functional redundancy of MGP2–10 suggest that they constitute a novel highly divergent protein family. Our data indicates that MGP2–10 function both as the primary amino acid resource for the developing larva and in the maintenance of milk homeostasis, similar to the function of the mammalian casein family of milk proteins. This study underscores the dynamic nature of the lactation cycle and identifies a novel family of lactation-specific proteins, unique to Glossina sp., that are essential to larval development. The specificity of MGP2–10 to tsetse and their critical role during lactation suggests that these proteins may be an excellent target for tsetse-specific population control approaches. Author Summary Tsetse flies are the sole vector for African trypanosomes, causative agents of sleeping sickness in humans and nagana in cattle. Transcriptome and proteome analyses were utilized to examine the underlying mechanisms of tsetse lactation that occur during each reproductive cycle. These analyses revealed a dramatic shift to the synthesis of milk proteins during lactation and a novel milk-specific protein family. All members of this family were co-localized, shared sequence similarity and were expressed at 40× basal levels during milk secretion. Suppression of gene from this lactation-associated family impaired progeny development by reducing milk protein content and altering milk homeostasis. These novel genes represent an excellent target for tsetse-specific reproductive-based control mechanisms. In addition, the characterization of tsetse milk production revealed multiple factors that are functionally analogous between tsetse and mammalian lactation.
【초록키워드】 Transcriptome, Human, Genome, variant, lactation, Proteins, metabolism, Protein, specificity, Region, African, Transferrin, female, mechanisms, proteome, synthesis, cattle, genomic, resource, Critical, mechanism, homeostasis, Amino acid, lipid metabolism, protein synthesis, Interference, maintenance, tsetse flies, amino acid sequence, control mechanisms, sleeping sickness, causative agents, tsetse fly, characterization, Factor, approaches, suppression, enrichment, secretion, coding, similarities, transcripts, sequence similarity, knockdown, RNA-seq data, protein level, Differential analysis, tsetse, fecundity, progeny, while, mammalian, transcript, mother s milk, Seven, shown, identify, addition, provided, reduced, functional, indicate, occur, unique, reducing, analysis, to define, reduce, were expressed, reproductive, genes encoding, casein, lactating, organized, 【제목키워드】 RNA-Seq, family, target, novel, insect, Potential, Identified, Abortifacient, Viviparous,