Biology subjects

Okude, G.

Publications and source records attributed to Okude, G..

3 recordsLinked to original sources

bioRxiv2023

A novel monocarboxylate transporter involved in 3-hydroxykynurenine transport for ommochrome coloration

Ommochromes are widespread pigments in invertebrates utilized for screening pigments in compound eyes and for reddish coloration in epidermis and wings. Ommochromes are derived from 3-hydroxykynurenine (3OHK), which is incorporated into cells from hemolymph or synthesized from tryptophan within cells. While the synthetic pathway from tryptophan to 3OHK has been well characterized, the gene responsible for cellular uptake of 3OHK has been poorly understood. In the silkworm Bombyx mori, adult compound eyes and eggs contain a mixture of ommochrome pigments. By using positional cloning method, we found that a novel monocarboxylate transporter, 3-hydroxykynurenine transporter (3OHKT), is responsible for the recessive mutant maternal brown of Tsujita (b-t) of B. mori. In b-t mutant, the color of the eggs is light brown, whereas the color of the compound eyes is normal, and we identified a 2-kb deletion in 3OHKT gene. TALEN-mediated knockout of 3OHKT gene produced the same coloration phenotype as b-t mutant, and the complementation test between b-t mutant and 3OHKT knockout strain proved that 3OHKT is responsible for b-t phenotype. 3OHKT protein was localized in the cellular membrane, and LC-MS analysis indicated that the uptake of 3OHK from hemolymph into the ovary was suppressed in the b-t mutant. Moreover, we confirmed that 3OHKT gene is specifically expressed at the reddish region and the time of pigmentation in the pupal wing of nymphalid butterflies. RNA interference of 3OHKT prevented reddish pigmentation in wings, highlighting its general involvement in ommochrome-based pigmentation other than compound eyes. SignificanceOmmochromes are widely distributed pigments in invertebrates and are synthesized from intracellular tryptophan or 3-hydroxykynurenine (3OHK). Ommochrome-based red markings on butterfly wings are often used for sexual selection, warning colors and mimicry. Most genes involved in the ommochrome synthesis pathway have been elucidated from analyses of eye color mutants in Drosophila. However, this study reveals that the ommochrome synthesis pathway has a different genetic repertoire depending on the tissues, and that the novel monocarboxylate transporter identified in this study has a major role in ommochrome pigmentation other than in compound eyes. In particular, our results suggest that classical ommochrome-related genes are rarely involved in the wing pigmentation of the nymphalid butterflies.

genetics↗

bioRxiv2022

Cuticle supplementation and nitrogen recycling by a dual bacterial symbiosis in a family of xylophagous beetles (Coleoptera: Bostrichidae)

Many insects engage in stable nutritional symbioses with bacteria that supplement limiting essential nutrients to their host. While several plant sap-feeding Hemipteran lineages are known to be simultaneously associated with two or more endosymbionts with complementary biosynthetic pathways to synthesize amino acids or vitamins, such co-obligate symbioses have not been functionally characterized in other insect orders. Here, we report on the characterization of a dual co-obligate, bacteriome-localized symbiosis in a family of xylophagous beetles using comparative genomics, fluorescence microscopy, and phylogenetic analyses. Across the beetle family Bostrichidae, all investigated species harbored the Bacteroidota symbiont Shikimatogenerans bostrichidophilus that encodes the shikimate pathway to produce tyrosine precursors in its severely reduced genome, likely supplementing the beetles cuticle biosynthesis, sclerotisation, and melanisation. One clade of Bostrichid beetles additionally housed the co-obligate symbiont Bostrichicola ureolyticus that is inferred to complement the function of Shikimatogenerans by recycling urea and provisioning the essential amino acid lysine, thereby providing additional benefits on nitrogen-poor diets. Both symbionts represent ancient associations within the Bostrichidae that have subsequently experienced genome erosion and co-speciation with their hosts. While Bostrichicola was repeatedly lost, Shikimatogenerans has been retained throughout the family and exhibits a perfect pattern of co-speciation. Our results reveal that co-obligate symbioses with complementary metabolic capabilities occur beyond the well-known sap-feeding Hemiptera and highlight the importance of symbiont-mediated cuticle supplementation and nitrogen recycling for herbivorous beetles. Significance statementNutritional symbioses evolved frequently in insects and contribute diverse metabolites to their hosts physiology. Associations with dual symbionts providing complementary nutrients evolved in multiple Hemiptera lineages, compensating eroded biosynthetic capabilities of primary symbionts. Bostrichidae, a family of xylophagous beetles, harbor consistently a Flavobacterial symbiont encoding exclusively the Shikimate pathway to synthesis precursors of tyrosine. However, in two families a second, closely Flavobacterial symbiont capable of recycling urea and synthesizing lysine was retained. Both symbionts exhibit high genomic syntheny and tight co-cladogenesis with the host phylogeny, indicating ancestral, ecological highly beneficial symbioses.

evolutionary biology↗

bioRxiv2020

Involvement of the doublesex gene in body color masculinization of the blue-tailed damselfly, Ischnura senegalensis

Odonata (dragonflies and damselflies) display remarkable color pattern diversity including sexual dimorphism and intrasexual polymorphism. We previously found that expression of a sex-determining transcription factor, the doublesex (dsx) gene, is associated with female color polymorphism (gynomorph for female-specific color and andromorph for male mimicking color) in the blue-tailed damselfly, Ischnura senegalensis. Here we investigate the function of dsx gene on thoracic coloration by electroporation-mediated RNA interference (RNAi). RNAi of the dsx common region changed color patterns of males and andromorphic females to patterns of gynomorphic females. Further, gynomorphic color pattern was not affected by dsx RNAi. The long isoform of dsx RNAi produced no effects, suggesting that the short isoform of dsx is important for body color masculinization in both males and andromorphic females. Expression pattern changes were also examined in five genes with different expression levels between sexes and female morphs. Among these genes are two melanin suppressing genes, black and ebony, that were upregulated in the dsx-RNAi region compared to a control region. Upregulation coincides with a gynomorphic orange color instead of the black stripe observed in males and andromorphic females. dsx may regulate male color differentiation by suppressing black and ebony in the thoracic region of I. senegalensis. Results add to the understanding of molecular mechanisms underlying the evolution of female polymorphism in Odonata.

genetics↗