Cyclorraphan yolk proteins and lepidopteran minor yolk proteins originate from two unrelated lipase families

Abstract

Vitellogenins, cyclorraphan yolk proteins and lepidopteran minor yolk proteins are three classes of female-specific proteins that serve as an embryonic nutritional store. Similarity to vertebrate lipid-binding proteins was established for vitellogenins and yolk proteins, vitellogenins being related to apolipoprotein B and yolk proteins to lipases. Recently, similarity between yolk proteins and minor yolk proteins was reported and it was suggested that yolk proteins are more related to minor yolk proteins than to vertebrate lipases. In this study, we cloned five additional yolk proteins from the grey fleshfly Neobellieria bullata, formerly known as Sarcophaga bullata. We used this sequence data, combined with sequence data retrieved from the NCBI protein database to evaluate the yolk protein-lipase and the yolk protein-minor yolk protein relationship. We found no similarity between yolk proteins and minor yolk proteins, but we showed that yolk proteins are related to a family of lipases containing vertebrate hepatic and pancreatic lipases while minor yolk proteins are related to a family of lipases containing vertebrate gastric and lingual lipases. The fact that three different classes of yolk storage proteins show similarity to three different classes of vertebrate lipid-binding proteins strongly suggests that this lipid-binding feature is important for insect yolk storage proteins.

Genome Sequence of the Tsetse Fly ( Glossina morsitans ): Vector of African Trypanosomiasis

“…Glossina, Drosophila , and other Brachyceran flies use lipase-derived yolk proteins for vitellogenesis, unlike non-Brachyceran flies that use the vitellogenin family of yolk proteins (31). Drosophila and Brachyceran flies outside of the Hippoboscidae superfamily produce multiple oocytes per gonotrophic cycle.…”

“…Unlike Drosophila , which has three yolk protein genes ( yp1 , yp2 , and yp3 ) localized on the X chromosome, Glossina has a single yolk protein gene, which is orthologous to Drosophila yp2 ( GMOY002338 ), expressed only in the ovaries, and lacks fat body–associated expression. Multiple yolk proteins have been identified in other Brachyceran flies, indicating that Glossina may have lost these genes in association with its reduction in reproductive capacity (31). …”

Organisation and expression of a cluster of yolk protein genes in the Australian sheep blowfly, Lucilia cuprina

“…2). The LcYP proteins are most similar (76-77% identity) to the YPB protein from Calliphora erythrocephala (also known as Calliphora vicina) (Martinez and Bownes 1994) and yolk protein E from Sarcophaga bullata (Hens et al 2004). This is perhaps not surprising as C. erythrocephala, S. bullata and L. cuprina all belong to the superfamily Oestroidea.…”

“…The SbYP proteins are not as closely related to each other as are the LcYP proteins. Pairwise comparisons show that the SbYP proteins fall into three groups based on degree of similarity (Hens et al 2004). Group one consists of SbYPA and SbYPE, group two SbYPB and SbYPC and group three contains SbYPD alone.…”

Adenotrophic Viviparity in Tsetse Flies: Potential for Population Control and as an Insect Model for Lactation

“…Brachyceran fly species produce lipase-derived yolk proteins (57, 117). Most species have multiple yolk protein genes, two to five depending on the species (19, 57, 87). However, tsetse is unique in that it carries only a single yolk protein gene orthologous to Drosophila yp2 (6).…”