Tyrosine metabolism for insect cuticle tanning

Abstract

Insects have become one of the most successful animal groups in diversity and numbers through the development of a multifunctional exoskeleton and skin, which must be shed periodically in order for them to grow and develop into adults. The evolutionary choice of certain structural materials for the assembly and stabilization of a cuticle with remarkable mechanical and chemical properties has allowed insects to invade terrestrial environments and to evolve flight mechanics for dispersion relatively early in geological history. Diphenolic compounds derived from tyrosine play a central role in sclerotization or tanning of the new cuticle. The phenolic amino acid is stored during larval feeding, and it i s mobilized for the production of both structural proteins and diphenolic tanning precursors that are transported into the cuticle. The latter compounds permeate the cuticle and serve as precursors for quinonoid derivatives that both sclerotize and pigment the exoskeleton.This report focuses on how tyrosine and derived diphenolic structures are stored as inactive molecules in preecdysial stages, and how they are released and metabolized to tanning chemicals that stabilize the new cuticle.

A Binding Site for the Transcription Factor Grainyhead/Nuclear Transcription Factor-1 Contributes to Regulation of theDrosophila Proliferating Cell Nuclear Antigen Gene Promoter

“…GRH is expressed in cuticle secreting cells during embryogenesis (32) and one of the putative target genes in these cells is the dopa decarboxylase (Ddc) gene, which is essential for cuticle formation (35,50). GRH also appears to function as a transcriptional activator to regulate several other genes involved in epidermal development, including Ultrabithorax (Ubx), engrailed, and fushi tarazu (ftz) (33,49,51).…”

Development and evolution of insect pigmentation: Genetic mechanisms and the potential consequences of pleiotropy

“…In butterflies, epidermal wounding can induce the formation of pigments other than black-brown melanin [65], but the purpose and underlying mechanism of this induction are unknown. As structural components of the insect cuticle, pigments contribute to the physical barrier that protects the insect body [66]. When this barrier is penetrated, melanization is used to encapsulate the foreign object and prevent infection [67].…”

Identification and characterization of Grainyhead‐like epithelial transactivator (GET‐1), a novel mammalian Grainyhead‐like factor

“…In fly larvae, a single-layer epidermis produces and secretes the proteinaceous, extracellular cuticle, which provides mechanical strength (Kramer and Hopkins, 1987). By contrast, in mammals, the epidermis and hair follicles are multilayered differentiating epithelial structures that produce a tough intracellular cytoskeleton (Eckert et al, 1997).…”

“…The Grainyhead gene is essential for fly development, as Grainyhead-mutated embryos do not hatch, have flimsy cuticles, grainy and discontinuous head skeletons, and patchy tracheal tubes (Bray and Kafatos, 1991). One of the direct Grainyhead targets in epidermis is the dopa decarboxylase gene, whose gene product is required for cuticle hardening and coloring (Kramer and Hopkins, 1987). Several other genes involved in epidermal development may also be targets of Grainyhead, including Ultrabithorax, Engrailed, and Fushi tarazu (Dynlacht et al, 1989).…”