Resilin is a member of a family of elastic proteins that includes elastin, as well as gluten, gliadin, abductin and spider silks. Resilin is found in specialized regions of the cuticle of most insects, providing low stiffness, high strain and efficient energy storage; it is best known for its roles in insect flight and the remarkable jumping ability of fleas and spittle bugs. Previously, the Drosophila melanogaster CG15920 gene was tentatively identified as one encoding a resilin-like protein (pro-resilin). Here we report the cloning and expression of the first exon of the Drosophila CG15920 gene as a soluble protein in Escherichia coli. We show that this recombinant protein can be cast into a rubber-like biomaterial by rapid photochemical crosslinking. This observation validates the role of the putative elastic repeat motif in resilin function. The resilience (recovery after deformation) of crosslinked recombinant resilin was found to exceed that of unfilled synthetic polybutadiene, a high resilience rubber. We believe that our work will greatly facilitate structural investigations into the functional properties of resilin and shed light on more general aspects of the structure of elastomeric proteins. In addition, the ability to rapidly cast samples of this biomaterial may enable its use in situ for both industrial and biomedical applications.

The factors that control replication rate of the intracellular bacterium Wolbachia pipientis in its insect hosts are unknown and difficult to explore, given the complex interaction of symbiont and host genotypes. Using a strain of Wolbachia that is known to over-replicate and shorten the lifespan of its Drosophila melanogaster host, we have tracked the evolution of replication control in both somatic and reproductive tissues in a novel host͞Wolbachia association. After transinfection (the transfer of a Wolbachia strain into a different species) of the over-replicating Wolbachia popcorn strain from D. melanogaster to Drosophila simulans, we demonstrated that initial high densities in the ovaries were in excess of what was required for perfect maternal transmission, and were likely causing reductions in reproductive fitness. Both densities and fitness costs associated with ovary infection rapidly declined in the generations after transinfection. The early death effect in D. simulans attenuated only slightly and was comparable to that induced in D. melanogaster. This study reveals a strong host involvement in Wolbachia replication rates, the independence of density control responses in different tissues, and the strength of natural selection acting on reproductive fitness. W olbachia pipientis are common bacterial endosymbionts of arthropods and filarial nematodes. They occur intracellularly in the ovaries of all described hosts, as well as in a number of other tissues depending on the particular Wolbachia͞host combination (1, 2). Infection of the host germ line enables transovarial transmission as well as induction of a number of reproductive abnormalities. These include cytoplasmic incompatibility (CI), parthenogenesis, feminization, and male killing, all of which enhance the spread of Wolbachia in host populations (3).In Drosophila simulans and Drosophila melanogaster, most infections induce CI (4), where Wolbachia modify developing sperm such that only the presence of the same Wolbachia strain in the egg can rescue the modification, allowing successful completion of karyogamy (5, 6) and the subsequent normal development of the embryo. Uninfected females cannot rescue the sperm modification, and so the development of their offspring is blocked. The result is that with each subsequent generation, infection frequencies rise and fewer and fewer uninfected females can successfully reproduce (7).For infections to be maintained in host populations, Wolbachia replication rates must be sufficiently high to ensure fidelity of transovarial transmission, while being low enough to not cause overt host pathology. This replication control can be considered a defining feature that separates vertically transmitted symbionts from horizontally transmitted pathogens. The mechanisms that underlie control of Wolbachia replication and the extent to which this control is influenced by host or bacterial genotype are not well understood. Studies exploring the link between CI expression and Wolbachia infection densities have revealed tha...

Silks play a crucial role in the survival and reproduction of many insects. Labial glands, Malpighian tubules, and a variety of dermal glands have evolved to produce these silks. The glands synthesize silk proteins, which become semicrystalline when formed into fibers. Although each silk contains one dominant crystalline structure, the range of molecular structures that can form silk fibers is greater than any other structural protein group. On the basis of silk gland type, silk protein molecular structure, and the phylogenetic relationship of silk-producing species, we grouped insect silks into 23 distinct categories, each likely to represent an independent evolutionary event. Despite having diverse functions and fundamentally different protein structures, these silks typically have high levels of protein crystallinity and similar amino acid compositions. The substantial crystalline content confers extraordinary mechanical properties and stability to silk and appears to be required for production of fine protein fibers.

The peripheral nervous system (PNS) of the Drosophilaembryo is especially suited for investigating