Protein Crosslinking by Transglutaminase Controls Cuticle Morphogenesis in Drosophila

Transglutaminase (TG) plays important and diverse roles in mammals, such as blood coagulation and formation of the skin barrier, by catalyzing protein crosslinking. In invertebrates, TG is known to be involved in immobilization of invading pathogens at sites of injury. Here we demonstrate that Drosophila TG is an important enzyme for cuticle morphogenesis. Although TG activity was undetectable before the second instar larval stage, it dramatically increased in the third instar larval stage. RNA interference (RNAi) of the TG gene caused a pupal semi-lethal phenotype and abnormal morphology. Furthermore, TG-RNAi flies showed a significantly shorter life span than their counterparts, and approximately 90% of flies died within 30 days after eclosion. Stage-specific TG-RNAi before the third instar larval stage resulted in cuticle abnormality, but the TG-RNAi after the late pupal stage did not, indicating that TG plays a key role at or before the early pupal stage. Immediately following eclosion, acid-extractable protein from wild-type wings was nearly all converted to non-extractable protein due to wing maturation, whereas several proteins remained acid-extractable in the mature wings of TG-RNAi flies. We identified four proteins—two cuticular chitin-binding proteins, larval serum protein 2, and a putative C-type lectin—as TG substrates. RNAi of their corresponding genes caused a lethal phenotype or cuticle abnormality. Our results indicate that TG-dependent protein crosslinking in Drosophila plays a key role in cuticle morphogenesis and sclerotization

A single-amino-acid change of the gustatory receptor gene, Gr5a, has a major effect on trehalose sensitivity in a natural population of Drosophila melanogaster.

Variation in trehalose sensitivity and nucleotide sequence polymorphism of the Gr5a gene encoding the gustatory receptor to sugar trehalose were investigated in 152 male lines of Drosophila melanogaster collected from a natural population. Among the observed 59 segregating sites, some pairs of sites showed significant linkage disequilibrium. A single SNP, which results in the Ala218Thr amino acid change, was significantly associated with trehalose sensitivity, as previously suggested. Threonine at amino acid position 218 was found to be the ancestral form in D. melanogaster, suggesting that low trehalose sensitivity was an ancestral form with respect to the receptor function. There was large genetic variation in trehalose sensitivity. It was continuously distributed, indicating that trehalose sensitivity measured by the behavioral assay is a quantitative trait. These results suggest that apart from the Gr5a gene, other genetic factors contribute to variation in trehalose sensitivity. Nucleotide diversity (pi) and nucleotide variation (theta) per site were 0.00874 and 0.00590, respectively. Fu and Li's test and the MK test showed no significant departure from the expectation of selective neutrality in the Gr5a gene. However, we rejected selective neutrality by Tajima's test and Fay and Wu's test with the observed level of recombination. We discuss possible causes of the observed pattern of nucleotide variation in the gustatory receptor Gr5a gene

Data from: Inferences of evolutionary history of a widely distributed mangrove species, Bruguiera gymnorrhiza, in the Indo-West Pacific region

Inference of genetic structure and demographic history is fundamental issue in evolutionary biology. We examined the levels and patterns of genetic variation of a widespread mangrove species in the Indo-West Pacific region, Bruguiera gymnorrhiza, using ten nuclear gene regions. Genetic variation of individual populations covering its distribution range was low, but as the entire species it was comparable to other plant species. Genetic differentiation among the investigated populations was high. They could be divided into two genetic clusters: the West and East clusters of the Malay Peninsula. Our results indicated that these two genetic clusters derived from their ancestral population whose effective size of which was much larger compared to the two extant clusters. The point estimate of speciation time between B. gymnorrhiza and Bruguiera sexangula was two times older than that of divergence time between the two clusters. Migration from the West cluster to the East cluster was much higher than the opposite direction but both estimated migration rates were low. The past Sundaland and/or the present Malay Peninsula are likely to prevent gene flow between the West and East clusters and function as a geographical or land barrier