Unveiling the role of differential growth in 3D morphogenesis: An inference method to analyze area expansion rate distribution in biological systems

The three-dimensional (3D) morphologies of many organs in organisms, such as the curved shapes of leaves and flowers, the branching structure of lungs, and the exoskeletal shape of insects, are formed through surface growth. Although differential growth, a mode of surface growth, has been qualitatively identified as 3D morphogenesis, a quantitative understanding of the mechanical contribution of differential growth is lacking. To address this, we developed a quantitative inference method to analyze the distribution of the area expansion rate, which governs the growth of surfaces into 3D morphology. To validate the accuracy of our method, we tested it on a basic 3D morphology that allowed for the theoretical derivation of the area expansion rate distribution, and then assessed the difference between the predicted outcome and the theoretical solution. We also applied this method to complex 3D shapes and evaluated its accuracy through numerical experiments. The findings of the study revealed a linear decrease in error on a log-log scale with an increase in the number of meshes in both evaluations. This affirmed the reliability of the predictions for meshes that are sufficiently refined. Moreover, we employed our methodology to analyze the developmental process of the Japanese rhinoceros beetle Trypoxylus dichotomus, which is characterized by differential growth regulating 3D morphogenesis. The results indicated a notably high rate of area expansion on the left and right edges of the horn primordium, which is consistent with the experimental evidence of a higher rate of cell division in these regions. Hence, these findings confirm the efficacy of the proposed method in analyzing biological systems

Juvenile hormone acid O-methyltransferase in Drosophila melanogaster

Juvenile hormone (JH) acid O-methyltransferase (JHAMT) is the enzyme that transfers a methyl groupfrom S-adenosyl-L-methionine (SAM) to the carboxyl group of JH acids to produce active JHs in thecorpora allata. While the JHAMT gene was originally identified and characterized in the silkwormBombyx mori, no orthologs from other insects have been studied until now. Here we report on thefunctional characterization of the CG17330/DmJHAMT gene in the fruit fly Drosophila melanogaster.Recombinant DmJHAMT protein expressed in Escherichia coli catalyzes the conversion of farnesoic acidand JH III acid to their cognate methyl esters in the presence of SAM. DmJHAMT is predominantlyexpressed in corpora allata, and its developmental expression profile correlates with changes in the JHtiter. While a transgenic RNA interference against DmJHAMT has no visible effect, overexpression ofDmJHAMT results in a pharate adult lethal phenotype, similar to that obtained with application of JHanalogs, suggesting that the temporal regulation of DmJHAMT is critical for Drosophila development

RNA interference in Lepidoptera: an overview of successful and unsuccessful studies and implications for experimental design

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A hemimetabolous wing development suggests the wing origin from lateral tergum of a wingless ancestor

祖先の背中の肥大化が昆虫の翅を生んだ --150年来の昆虫翅進化の謎に迫る--. 京都大学プレスリリース. 2022-02-28.The origin and evolution of the novel insect wing remain enigmatic after a century-long discussion. The mechanism of wing development in hemimetabolous insects, in which the first functional wings evolved, is key to understand where and how insect wings evolutionarily originate. This study explored the developmental origin and the postembryonic dramatic growth of wings in the cricket Gryllus bimaculatus. We find that the lateral tergal margin, which is homologous between apterygote and pterygote insects, comprises a growth organizer to expand the body wall to form adult wing blades in Gryllus. We also find that Wnt, Fat-Dachsous, and Hippo pathways are involved in the disproportional growth of Gryllus wings. These data provide insights into where and how insect wings originate. Wings evolved from the pre-existing lateral terga of a wingless insect ancestor, and the reactivation or redeployment of Wnt/Fat-Dachsous/Hippo-mediated feed-forward circuit might have expanded the lateral terga

CRISPR/Cas9-based heritable targeted mutagenesis in Thermobia domestica: A genetic tool in an apterygote development model of wing evolution

Despite previous developmental studies on basally branching wingless insects and crustaceans, the evolutionary origin of insect wings remains controversial. Knowledge regarding genetic regulation of tissues hypothesized to have given rise to wings would help to elucidate how ancestral development changed to allow the evolution of true wings. However, genetic tools available for basally branching wingless species are limited. The firebrat Thermobia domestica is an apterygote species, phylogenetically related to winged insects. T. domestica presents a suitable morphology to investigate the origin of wings, as it forms the tergal paranotum, from which wings are hypothesized to have originated. Here we report the first successful CRISPR/Cas9-based germline genome editing in T. domestica. We provide a technological platform to understand the development of tissues hypothesized to have given rise to wings in an insect with a pre-wing evolution body plan