Changes in composition and levels of hemolymph proteins provide insights to their functions in pharate, early and late pupae and adults of Manduca sexta

The tobacco hornworm, Manduca sexta, is a lepidopteran model species widely used to study insect biochemical processes. While some of its larval hemolymph proteins are well understood, a detailed proteomic analysis was unavailable until 2016, revealing features such as correlation with transcriptome data, formation of immune complexes, and constitution of an immune signaling system. Yet, it is unclear how these may change in other developmental stages. In this paper, we report the proteomes of cell-free hemolymph from prepupae, pupae on days 4 and 13, and young adults. Of the 1,824 proteins identified, 907 have a signal peptide and 215 are related to immunity. Drastic changes in abundance of the storage proteins, for instance, reflect physiological disparities among prepupae, pupae, and adults. Considerably more proteins lacking signal peptide are present in the late pupae, suggesting that plasma acts as a temporary reservoir for intracellular components released from remodeling tissues during metamorphosis. In summary, the proteins and their levels revealed in this study are expected to stimulate focused explorations of humoral immunity in wandering larvae, pupae, and adults of M. sexta and shed light upon functional and comparative genomic research in other holometabolous insects.