Editorial: Biological and physical basis of the development of integument and associated structures

Cédric Finet^1*Anupama Prakash^2*

• ¹National University of Singapore, Singapore, Singapore
• ²Imperial College London, London, England, United Kingdom

The morphogenesis of integumentary surfaces and nanostructures remains a vast and underexplored field. However, the emergence of recent reviews (Airoldi et al., 2019;Lloyd and Nadeau, 2021;Saranathan and Finet, 2021;Finet, 2024) and research papers on this topic highlights an active field of research. Our understanding of the spatial control of chitin assembly at the subcellular level has progressed (Pesch et al., 2017;Adler, 2019;Sviben et al., 2020;De Giorgio et al., 2023;Ghosh and Treisman, 2024;Ikeda et al., 2024;Inagaki et al., 2024;Itakura et al., 2024). Single-cell gene expression atlases of developing scales in butterflies (Prakash et al., 2024;Loh et al., 2025) and bristles in Drosophila (Hopkins et al., 2023) have identified gene networks involved in hair-like structure morphogenesis. Progress has been made to understand the formation of different nanostructures in butterfly wing scales such as the laminae (Thayer et al., 2020;Prakash et al., 2022;Chatterjee et al., 2023;Balakrishnan et al., 2024), the ridges (Brien et al., 2022;Ficarrotta et al., 2022;Lloyd et al., 2024;Totz et al., 2024), the luminal gyroid (Wilts et al., 2017), and the trabeculae (Ru et al., 2024). Work on cuticular proteins has identified their roles and spatial distributions in the development of beetle elytra (Noh et al., 2014;Murata et al., 2022;Bao et al., 2024) and butterfly scales (Liu et al., 2021).In particular, many studies feed into the biomimetic and bioengineering fields of research. For example, the natural world has inspired multiple solutions for material adhesion (Li et al., 2024). The morphology of shark scales has led to various applications from membrane antifouling to hydrodynamics (Ghimire et al., 2024), and chameleons and cephalopods have inspired colorchanging hydrogels for multiple functions including sensors (Lu et al., 2022;Zhang et al., 2023). However, beyond extracting design principles from biological materials, the ultimate goal would be to develop bio-inspired manufacturing processes, which require an in-depth understanding of the biological processes themselves. This topic explores the genetics and cellular mechanisms underlying the development of integument and associated structures in animals and plants. With this collection, we wish to direct readers to the emerging field of bio-inspired manufacturing and hope to acknowledge the need for more studies in understanding biological processes that can produce precise and compositionally driven micro-and nano-structures.Plant cell walls are made up of cellulose microfibrils embedded in a matrix of glycoproteins, and pectic and hemicellulosic polysaccharides. Glycosylphosphatidylinositol (GPI) is a common eukaryotic lipid modification that helps proteins adhere to the membrane lipid bilayer. Zhou reviews our knowledge on GPI-anchored proteins involved in cell wall regulation in the plant model Arabidopsis. The author proposes that these proteins might act as structural components of the cell wall by organizing cellulose microfibrils at the cell surface.In reptiles, a mutation in the TFEC gene leads to a piebald phenotype with white patches in the ball python while it causes reduced coloration in the brown anole lizard due to the loss of iridophores (Garcia-Elfring et al., 2023). Using comparative histology, Tzika demonstrates that TFEC mutants produce similar phenotypes of reduced coloration via different mechanisms. In the anole, TFEC is necessary for the development of iridophores, whereas in the ball python, which lacks iridophores, TFEC is important for the development of melanophores and xanthophores. By pointing out that the same transcription factor can function differently within the same taxon, this study emphasizes that the phenotypic mutant approach is insufficient for elucidating the underlying molecular mechanisms.Like reptiles, the ribbontail stingray exhibits structurally colored blue spots produced by dermal iridophores. These iridophores are unique by having numerous fingerlike protuberances (Surapaneni et al., 2024) and contain spherical iridosomes enclosing guanine nanocrystals. Blumer, Surapaneni et al. provide a detailed ultrastructural description of the ribbontail ray's novel iridophore. They found that intermediate filaments form an intracellular scaffold that spaces the iridosomes within the iridophores.In crickets and grasshoppers, males have evolved cuticular structures on their forewings to produce sound via stridulation. Turchyn and Popadić identify the POU homeodomain gene nubbin as a regulator of the development of sound resonators on the wings of the house cricket. They propose that nubbin, a key player in the wing development network, has been recruited in the course of evolution of Orthoptera to evolve these new cuticular nanostructures. Banerjee, Finet et al. investigate the interplay between nanomorphology and pigmentation during the development of butterfly scales. They show that the loss-of-function mutations in Optix result in both pigmentation and nanomorphology defects. By comparing these effects with mutants in melanin and/or ommochrome pathways, they propose that Optix regulates nanomorphology via its effects on pigmentation, complementing earlier studies on melanized (Matsuoka and Monteiro, 2018) and silver scales (Prakash et al., 2022).