Biology subjects

Kawahara, A.

Publications and source records attributed to Kawahara, A..

3 recordsLinked to original sources

bioRxiv2025

Evolution of highly repetitive silk genes in the Luna moth, Actias luna

Gene duplications are a major driver of molecular diversification and phenotypic evolution. Arthropod silk genes provide an excellent model for studying these processes due to their highly repetitive sequences and rapid evolutionary rates. In Lepidoptera, the Fibroin heavy chain (fibH) gene encodes the primary structural protein for silk fibers, contributing largely to their mechanical strength. This inner fibroin core is surrounded by an outer coating composed primarily of sericins. Sericins are a group of highly repetitive, serine-rich proteins that modulate silk fiber properties. Although sericins in the Domesticated silkworm (Bombyx mori) have been associated with life stage-specific variation in silk characteristics, their evolution and function across Lepidoptera remain poorly understood. Here, we provide a detailed molecular characterization of sericin genes in the Luna moth (Actias luna), a saturniid species known for forming dense, robust, silk-woven cocoons. We identified eight sericin genes that (1) are frequently arranged into clusters of closely related paralogs, (2) exhibit considerable variation in repeat number and amino acid composition, and (3) display distinct gene expression patterns across life stages. A comparison of sericin genes across Saturniidae and Bombycidae reveals evidence for convergent subfunctionalization. These findings suggest that sericin gene duplications enable dynamic shifts in silk composition both within and between species, potentially reflecting adaptive responses to ecological and functional demands. Significance StatementGene duplications are thought to be a major driver of molecular diversification and phenotypic evolution. Arthropod silk genes, characterized by their repetitive sequences and rapid evolution, provide an ideal model for studying these processes. Sericins, a group of highly repetitive, serine-rich silk proteins, are hypothesized to have contributed to the diversification of silk properties, both within and across lepidopteran species. However, their diversity and evolution is poorly understood. Focusing on the Luna moth (Actias luna), we show that sericin gene duplications across Saturniidae have led to subfunctionalization, enabling changes to silk composition. These modifications may represent adaptative responses to ecological and functional demands.

evolutionary biology↗

bioRxiv2021

A complex interplay between balancing selection and introgression maintains a genus-wide alternative life-history strategy.

Alternative life-history strategies (ALHS) are genetic polymorphisms generating phenotypes differing in life histories that generally arise due to metabolic resource allocation tradeoffs. Althouigh ALHS are often be limited to a single sex or populations of a species, they can, in rare cases, be found among several species across a genus. In the butterfly genus Colias, at least a third of the species have a female limited ALHS called Alba. While many females develop brightly pigmented wings, Alba females reallocate nitrogen resources used in pigment synthesis to reproductive development, producing white-winged, more fecund females. Whether this ALHS evolved once or many times, and whether it has moved among species via introgression or been maintained via long-term balancing selection, has not been established. Answering these questions presents an opportunity to investigate the genetic basis and evolutionary forces acting upon ALHS, which have rarely been studied at a genus level. Here we identify the genetic locus of Alba in a second Colias species, allowing us to compare this with previous results in a larger phylogenetic context. Our findings suggest Alba has a singular origin and has been maintained in Colias through a combination of balancing selection and introgression for nearly one million years and at least as many generations. Finally, using CRISPR/Cas9 deletions in the cis-regulatory region of the Alba allele, we demonstrate that the Alba allele is a modular enhancer for the BarH1 gene and is necessary for the induction of the ALHS, which potentially facilitates its long-term persistence in the genus.

evolutionary biology↗

bioRxiv2020

Cross-ecosystem transcriptomics identifies distinct genetic modules for nutrient acquisition in maize

Plants have evolved diverse strategies for the acquisition of the macro-nutrients phosphorus and nitrogen; e.g., mycorrhizal formation, root development, and secretion of chelators/hydrolases to liberate inorganic phosphate. Despite the extensive studies on the individual strategies, there is little information about how plants regulate these strategies in response to fluctuating environment. We approached this issue via profiling transcriptomes of plants grown in large environmental gradients. Roots, leaves, and root-zone soils of 251 maize plants were collected across the US Corn Belt and Japan. RNA was extracted from the roots and sequenced, and the leaves and soils were analyzed. Nineteen genetic modules were defined by weighted gene coexpression network analysis and functionally characterized according to gene ontology analysis, by which we found three modules that are directly involved in nutrient acquisition: mycorrhizal formation, phosphate-starvation response (PSR), and root development. Correlation analysis with soil and plant factors revealed that both phosphorus and nitrogen deficiencies upregulated the mycorrhizal module, whereas the PSR module was upregulated mainly by deficiency in phosphorus relative to nitrogen. Expression levels of the root development module were negatively correlated with those of the mycorrhizal module, suggesting that nutrient acquisition through the two pathways, mycorrhizas and roots, are opposite strategies that are employed under nutrient-deficient and -enriched conditions, respectively. The identification of the soil and plant factors that drive the modules has implications for sustainable agriculture; activation/optimization of the strategies is feasible via manipulating the factors. Overall, our study opens a new window for understanding plant response to complex environments.

plant biology↗