The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
John H. Law - One of the best experts on this subject based on the ideXlab platform.
-
Hemolymph titers, chromophore association and immunological cross-reactivity of an Ommochrome-binding protein from the hemolymph of the tobacco hornworm, Manduca sexta
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Ralph R. Martel, John H. LawAbstract:Abstract A yellow-colored Ommochrome-binding protein (OBP) isolated from the hemolymph of the tobacco hornworm, Manduca sexta , appears to derive its color from ommatin D. Ommatin D is the sulfate ester of xanthommatin, the latter being an important metabolite of tryptophan in insects. The polypeptide chain of OBP was immunologically detected in the hemolymph at all stages of the life cycle. However, only during the fifthlarval instar did OBP polypeptide levels in the hemolymph appreciate significantly. The highest OBP polypeptide concentration (approx. 0.45 mg/ml) was observed on the first day of pupation. Thereafter, the concentration of OBP polypeptide gradually decreased in pupal hemolymph. We found that association of chromophore with the OBP polypeptide was transient. In fifth instar wandering stage larvae and in female months, OBP was detectable in the hemolymph. In feeding fifth instar larvae and in male months, only apoOBP was detected (i.e. the OBP polypeptide without the chromophore). During the wandering stage, increasing amounts of chromophore became associated with the OBP polypeptide. No representatives of seven other insect orders contained hemolymph proteins that cross-reacted with anti-OBP antiserum. However, when four other Lepidopteran species were examined, an immunologically-related hemolymph protein of approx. 31 kDa was detected in each animal. Whether these cross-reacting proteins also bind Ommochromes remains to be investigated.
-
Purification and properties of an Ommochrome-binding protein from the hemolymph of the tobacco hornworm, Manduca sexta.
The Journal of biological chemistry, 1991Co-Authors: Ralph R. Martel, John H. LawAbstract:Abstract A yellow-colored protein (YCP) was isolated from the hemolymph (i.e. blood) of fifth instar wandering stage larvae of Manduca sexta. The molecular mass of YCP was 31 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel filtration chromatography suggested that native YCP was a monomer. The absorbance spectrum of YCP revealed maxima at 278 and 405 nm. Chromophore was released from YCP through denaturation of the protein with methanol and chloroform. In neutral solution and in acid, the released chromophore showed the absorbance characteristics of an Ommochrome: ommatin D. In addition, the chromophore was sensitive to treatment with arylsulfatase as would be expected for ommatin D. The amino acid composition and the N-terminal sequence of YCP were determined. The YCP polypeptide chain was found to be glycosylated. Carbohydrate analysis suggested that Man and GlcNAc were present in a 3:1 ratio. Circular dichroism indicated that YCP consisted of 68% beta-pleated sheet with no alpha-helices being detected. An in vitro incubation of larval fat body in the presence of [35S]methionine indicated that this organ was the site of synthesis. Ommochromes arise in insects as end products of the metabolism of tryptophan. It is well-documented that Ommochromes occur in both the tissues and the excreta of insects. We propose that in M. sexta, one such tryptophan metabolite is found in the hemolymph associated with a specific protein.
T Tamura - One of the best experts on this subject based on the ideXlab platform.
-
Positional cloning of a Bombyx pink-eyed white egg locus reveals the major role of cardinal in Ommochrome synthesis
Heredity, 2016Co-Authors: M Osanai-futahashi, K-i Tatematsu, R Futahashi, J Narukawa, Y Takasu, T Kayukawa, T Shinoda, T Ishige, S Yajima, T TamuraAbstract:Ommochromes are major insect pigments involved in coloration of compound eyes, eggs, epidermis and wings. In the silkworm Bombyx mori , adult compound eyes and eggs contain a mixture of the Ommochrome pigments such as ommin and xanthommatin. Here, we identified the gene involved in Ommochrome biosynthesis by positional cloning of B. mori egg and eye color mutant pink-eyed white egg ( pe ). The recessive homozygote of pe has bright red eyes and white or pale pink eggs instead of a normal dark coloration due to the decrease of dark Ommochrome pigments. By genetic linkage analysis, we narrowed down the pe -linked region to ~258 kb, containing 17 predicted genes. RNA sequencing analyses showed that the expression of one candidate gene, the ortholog of Drosophila haem peroxidase cardinal , coincided with egg pigmentation timing, similar to other Ommochrome-related genes such as Bm-scarlet and Bm-re . In two pe strains, a common missense mutation was found within a conserved motif of B. mori cardinal homolog ( Bm-cardinal ). RNA interference-mediated knockdown and transcription activator-like effector nuclease (TALEN)-mediated knockout of the Bm-cardinal gene produced the same phenotype as pe in terms of egg, adult eye and larval epidermis coloration. A complementation test of the pe mutant with the TALEN-mediated Bm-cardinal- deficient strain showed that the mutant phenotype could not be rescued, indicating that Bm-cardinal is responsible for pe . Moreover, knockdown of the cardinal homolog in Tribolium castaneum also induced red compound eyes. Our results indicate that cardinal plays a major role in Ommochrome synthesis of holometabolous insects.
-
Identification of the Bombyx Red Egg Gene Reveals Involvement of a Novel Transporter Family Gene in Late Steps of the Insect Ommochrome Biosynthesis Pathway
The Journal of biological chemistry, 2012Co-Authors: M Osanai-futahashi, K-i Tatematsu, J Narukawa, T Kayukawa, T Shinoda, T Tamura, Kimiko Yamamoto, Keiro Uchino, Yutaka Banno, Hideki SezutsuAbstract:Ommochromes are one of the major pigments involved in coloration of eggs, eyes, and body surface of insects. However, the molecular mechanisms of the final steps of Ommochrome pigment synthesis have been largely unknown. The eggs of the silkworm Bombyx mori contain a mixture of Ommochrome pigments, and exhibit a brownish lilac color. The recessive homozygous of egg and eye color mutant, red egg (re), whose eggs display a pale orange color instead of normal dark coloration, has been long suggested to have a defect in the biosynthesis of the final Ommochrome pigments. Here, we identify the gene responsible for the re locus by positional cloning, mutant analysis, and RNAi experiments. In the re mutants, we found that a 541-bp transposable element is inserted into the ORF of BGIBMGA003497-1 (Bm-re) encoding a novel member of a major facilitator superfamily transporter, causing disruption of the splicing of exon 9, resulting in two aberrant transcripts with frameshifts yielding nonfunctional proteins lacking the C-terminal transmembrane domains. Bm-re function in pigmentation was confirmed by embryonic RNAi experiments. Homologs of the Bm-re gene were found in all insect genomes sequenced at present, except for 12 sequenced Drosophila genomes, which seemed to correlate with the previous studies that have demonstrated that eye Ommochrome composition is different from other insects in several Dipterans. Knockdown of the Bm-re homolog by RNAi in the red flour beetle Tribolium castaneum caused adult compound eye coloration defects, indicating a conserved role in Ommochrome pigment biosynthesis at least among holometabolous insects.
-
Positional cloning of silkworm white egg 2 (w‐2) locus shows functional conservation and diversification of ABC transporters for pigmentation in insects
Genes to cells : devoted to molecular & cellular mechanisms, 2011Co-Authors: K-i Tatematsu, J Narukawa, T Tamura, Kimiko Yamamoto, Keiro Uchino, Yutaka Banno, Tetsuya Iizuka, Susumu Katsuma, Toru Shimada, Hideki SezutsuAbstract:The white, scarlet and brown genes of Drosophila melanogaster encode three half-type ATP-binding cassette (ABC) transporters. In Drosophila, precursors of Ommochromes and pteridines are transported by White/Scarlet and White/Brown heterodimers, respectively. The white egg 2 (w-2) mutant of the silkworm, Bombyx mori, has white eggs and eyes because of lack of Ommochrome granules in the serosa and eyes. Here, we report that the silkworm w-2 locus encodes an ortholog of Drosophila scarlet. Our results indicate that Bombyx Scarlet forms a heterodimer with Bombyx White to transport Ommochrome precursors, suggesting that formation of a White/Scarlet heterodimer and its involvement in the transport of Ommochrome precursors are evolutionarily ancient and widely conserved traits in insects. Contrary to dipteran insects, white and scarlet were juxtaposed in a head-to-tail orientation in the silkworm genome, suggesting that the origin of white and scarlet was a tandem duplication of their ancestral transporter gene. In Bombyx, White is also essential for the transport of uric acid in larval epidermis. However, our results suggest that a Bombyx White/Scarlet heterodimer is not involved in this process. Our results emphasize the functional conservation and diversification of half-type ABC transporter families in insects, which may contribute to their extremely diverse color patterns.
-
A single-base deletion in an ABC transporter gene causes white eyes, white eggs, and translucent larval skin in the silkworm w-3oe mutant
Insect biochemistry and molecular biology, 2008Co-Authors: Natuo Kômoto, Hideki Sezutsu, Guo-xing Quan, T TamuraAbstract:The w-3(oe) silkworm mutant has white eyes and eggs due to the absence of Ommochrome pigments in the eye pigment cells and serosa cells. The mutant is also characterized by translucent larval skin resulting from a deficiency in the transportation of uric acid, which acts as a white pigment in larval epidermal cells. A silkworm homolog of the fruitfly white gene, Bmwh3, a member of ATP-binding cassette transporter superfamily, was mapped on the w-3 locus. The w-3(oe) mutant has a single-base deletion in exon 2 and a premature stop codon at the 5' end of exon 3. These results show that w-3 is equivalent to Bmwh3 and is responsible for the transportation of Ommochrome precursors and uric acid into pigment granules and urate granules, respectively.
Ralph R. Martel - One of the best experts on this subject based on the ideXlab platform.
-
Hemolymph titers, chromophore association and immunological cross-reactivity of an Ommochrome-binding protein from the hemolymph of the tobacco hornworm, Manduca sexta
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Ralph R. Martel, John H. LawAbstract:Abstract A yellow-colored Ommochrome-binding protein (OBP) isolated from the hemolymph of the tobacco hornworm, Manduca sexta , appears to derive its color from ommatin D. Ommatin D is the sulfate ester of xanthommatin, the latter being an important metabolite of tryptophan in insects. The polypeptide chain of OBP was immunologically detected in the hemolymph at all stages of the life cycle. However, only during the fifthlarval instar did OBP polypeptide levels in the hemolymph appreciate significantly. The highest OBP polypeptide concentration (approx. 0.45 mg/ml) was observed on the first day of pupation. Thereafter, the concentration of OBP polypeptide gradually decreased in pupal hemolymph. We found that association of chromophore with the OBP polypeptide was transient. In fifth instar wandering stage larvae and in female months, OBP was detectable in the hemolymph. In feeding fifth instar larvae and in male months, only apoOBP was detected (i.e. the OBP polypeptide without the chromophore). During the wandering stage, increasing amounts of chromophore became associated with the OBP polypeptide. No representatives of seven other insect orders contained hemolymph proteins that cross-reacted with anti-OBP antiserum. However, when four other Lepidopteran species were examined, an immunologically-related hemolymph protein of approx. 31 kDa was detected in each animal. Whether these cross-reacting proteins also bind Ommochromes remains to be investigated.
-
Purification and properties of an Ommochrome-binding protein from the hemolymph of the tobacco hornworm, Manduca sexta.
The Journal of biological chemistry, 1991Co-Authors: Ralph R. Martel, John H. LawAbstract:Abstract A yellow-colored protein (YCP) was isolated from the hemolymph (i.e. blood) of fifth instar wandering stage larvae of Manduca sexta. The molecular mass of YCP was 31 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel filtration chromatography suggested that native YCP was a monomer. The absorbance spectrum of YCP revealed maxima at 278 and 405 nm. Chromophore was released from YCP through denaturation of the protein with methanol and chloroform. In neutral solution and in acid, the released chromophore showed the absorbance characteristics of an Ommochrome: ommatin D. In addition, the chromophore was sensitive to treatment with arylsulfatase as would be expected for ommatin D. The amino acid composition and the N-terminal sequence of YCP were determined. The YCP polypeptide chain was found to be glycosylated. Carbohydrate analysis suggested that Man and GlcNAc were present in a 3:1 ratio. Circular dichroism indicated that YCP consisted of 68% beta-pleated sheet with no alpha-helices being detected. An in vitro incubation of larval fat body in the presence of [35S]methionine indicated that this organ was the site of synthesis. Ommochromes arise in insects as end products of the metabolism of tryptophan. It is well-documented that Ommochromes occur in both the tissues and the excreta of insects. We propose that in M. sexta, one such tryptophan metabolite is found in the hemolymph associated with a specific protein.
Jérôme Casas - One of the best experts on this subject based on the ideXlab platform.
-
Uncyclized xanthommatin is a key Ommochrome intermediate in invertebrate coloration
Insect biochemistry and molecular biology, 2020Co-Authors: Florent Figon, Thibaut Munsch, Cécile Croix, Marie-claude Viaud-massuard, Arnaud Lanoue, Jérôme CasasAbstract:Ommochromes are widespread pigments that mediate multiple functions in invertebrates. The two main families of Ommochromes are ommatins and ommins, which both originate from the kynurenine pathway but differ in their backbone, thereby in their coloration and function. Despite its broad significance, how the structural diversity of Ommochromes arises in vivo has remained an open question since their first description. In this study, we combined organic synthesis, analytical chemistry and organelle purification to address this issue. From a set of synthesized ommatins, we derived a fragmentation pattern that helped elucidating the structure of new Ommochromes. We identified uncyclized xanthommatin as the elusive biological intermediate that links the kynurenine pathway to the ommatin pathway within ommochromasomes, the Ommochrome-producing organelles. Due to its unique structure, we propose that uncyclized xanthommatin functions as a key branching metabolite in the biosynthesis and structural diversification of ommatins and ommins, from insects to cephalopods.
-
Electronic Couplings in the Reduced State Lie at the Origin of Color Changes of Ommochromes
2020Co-Authors: Florent Figon, Jérôme Casas, Ilaria Ciofini, Carlo AdamoAbstract:In the colorful world of pigments and dyes, the chemical reduction of chromophores usually leads to bleaching because of π-conjugation interruption. Yet, the natural phenoxazinone-based Ommochrome pigment called xanthommatin displays a bathochromic (i.e. red) shift upon two-electron reduction to its corresponding phenoxazine, whose electronic origins are not completely disclosed. In this study, we investigated, at quantum chemical level, a series of phenoxazinone/phenoxazine pairs that was previously explored by UV-Vis spectroscopy (Schäfer and Geyer, 1972), and which displays different hypsochromic and bathochromic shifts upon reduction. Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) have been applied to compute their optical properties in order to find a rational explanation of the observed photophysical behavior. Based on our results, we propose that the electro-accepting power of auxochromes and their conjugation facilitate intramolecular charge-transfers across the phenoxazine bridge by lowering unoccupied molecular orbitals via electronic and geometric couplings, leading ultimately to bathochromy. Our findings therefore suggest new potential ways to adjust the color-changing ability of phenoxazinones in technological contexts. Overall, this model extends our mechanistic understanding of the many biological functions of Ommochromes in invertebrates, from tunable color changes to antiradical behaviors.<br>
-
Uncyclized xanthommatin is a key Ommochrome intermediate in invertebrate coloration
2019Co-Authors: Florent Figon, Thibaut Munsch, Cécile Croix, Marie-claude Viaud-massuard, Arnaud Lanoue, Jérôme CasasAbstract:ABSTRACT Ommatins are widespread Ommochrome pigments mediating important functions in invertebrates. While the early biogenetic steps of ommatins are well known, how their pyrido[3,2-a]phenoxazinone chromophore is formed and modified in vivo remains an unanswered question. In this study, we combined organic synthesis, analytical chemistry and organelle purification to address this issue. We analyzed the metabolites of the tryptophan→Ommochrome pathway produced both in vitro and in vivo. We synthesized xanthommatin, the best-known ommatin, by oxidizing 3-hydroxykynurenine in vitro and we analytically characterized the products. We followed the thermal reactivity of synthesized ommatins in acidified methanol to screen for labile and altered compounds. We finally reinvestigated the Ommochromes of housefly eyes by purifying and extracting the Ommochrome-producing organelles called ommochromasomes. We found that the in vitro oxidative condensation of 3-hydroxykynurenine produces a mixture of ommatins, which readily undergo thermal reactions overtime. Our results suggest that the formation of decarboxylated ommatins might be regulated in vivo, while the methoxylation of ommatins, previously reported in biological extracts, are most likely always artifactitious. For the first time, we identified both in vitro and in vivo the elusive intermediate between 3-hydroxykynurenine and ommatins as being uncyclized xanthommatin. We hence confirm that ommatins are mainly biosynthesized by first the homodimerization of 3-hydroxykynurenine to the aminophenoxazinone uncyclized xanthommatin, and then an intramolecular cyclization to form the pyridine ring. We finally discuss the implication of the newly discovered uncyclized xanthommatin as a branching metabolite in the biosynthesis of Ommochromes, particularly of ommins in cephalopods.
-
biological identification and localization of uncyclized xanthommatin a key intermediate in Ommochrome biosynthesis an in vitro in vivo study
bioRxiv, 2019Co-Authors: Florent Figon, Thibaut Munsch, Cécile Croix, Arnaud Lanoue, Marieclaude Viaudmassuard, Jérôme CasasAbstract:ABSTRACT Ommatins are widespread Ommochrome pigments mediating important functions in invertebrates. While the early biogenetic steps of ommatins are well known, how their pyrido[3,2-a]phenoxazinone chromophore is formed and modified in vivo remains an unanswered question. In this study, we combined organic synthesis, analytical chemistry and organelle purification to address this issue. We analyzed the metabolites of the tryptophan→Ommochrome pathway produced both in vitro and in vivo. We synthesized xanthommatin, the best-known ommatin, by oxidizing 3-hydroxykynurenine in vitro and we analytically characterized the products. We followed the thermal reactivity of synthesized ommatins in acidified methanol to screen for labile and altered compounds. We finally reinvestigated the Ommochromes of housefly eyes by purifying and extracting the Ommochrome-producing organelles called ommochromasomes. We found that the in vitro oxidative condensation of 3-hydroxykynurenine produces a mixture of ommatins, which readily undergo thermal reactions overtime. Our results suggest that the formation of decarboxylated ommatins might be regulated in vivo, while the methoxylation of ommatins, previously reported in biological extracts, are most likely always artifactitious. For the first time, we identified both in vitro and in vivo the elusive intermediate between 3-hydroxykynurenine and ommatins as being uncyclized xanthommatin. We hence confirm that ommatins are mainly biosynthesized by first the homodimerization of 3-hydroxykynurenine to the aminophenoxazinone uncyclized xanthommatin, and then an intramolecular cyclization to form the pyridine ring. We finally discuss the implication of the newly discovered uncyclized xanthommatin as a branching metabolite in the biosynthesis of Ommochromes, particularly of ommins in cephalopods.
-
Ommochromes in invertebrates: biochemistry and cell biology.
Biological reviews of the Cambridge Philosophical Society, 2018Co-Authors: Florent Figon, Jérôme CasasAbstract:Ommochromes are widely occurring coloured molecules of invertebrates, arising from tryptophan catabolism through the so-called Tryptophan → Ommochrome pathway. They are mainly known to mediate compound eye vision, as well as reversible and irreversible colour patterning. Ommochromes might also be involved in cell homeostasis by detoxifying free tryptophan and buffering oxidative stress. These biological functions are directly linked to their unique chromophore, the phenoxazine/phenothiazine system. The most recent reviews on Ommochrome biochemistry were published more than 30 years ago, since when new results on the enzymes of the Ommochrome pathway, on Ommochrome photochemistry as well as on their antiradical capacities have been obtained. Ommochromasomes are the organelles where Ommochromes are synthesised and stored. Hence, they play an important role in mediating Ommochrome functions. Ommochromasomes are part of the lysosome-related organelles (LROs) family, which includes other pigmented organelles such as vertebrate melanosomes. Ommochromasomes are unique because they are the only LRO for which a recycling process during reversible colour change has been described. Herein, we provide an update on Ommochrome biochemistry, photoreactivity and antiradical capacities to explain their diversity and behaviour both in vivo and in vitro. We also highlight new biochemical techniques, such as quantum chemistry, metabolomics and crystallography, which could lead to major advances in their chemical and functional characterisation. We then focus on ommochromasome structure and formation by drawing parallels with the well-characterised melanosomes of vertebrates. The biochemical, genetic, cellular and microscopic tools that have been applied to melanosomes should provide important information on the ommochromasome life cycle. We propose LRO-based models for ommochromasome biogenesis and recycling that could be tested in the future. Using the context of insect compound eyes, we finally emphasise the importance of an integrated approach in understanding the biological functions of Ommochromes.
Hideki Sezutsu - One of the best experts on this subject based on the ideXlab platform.
-
Identification of the Bombyx Red Egg Gene Reveals Involvement of a Novel Transporter Family Gene in Late Steps of the Insect Ommochrome Biosynthesis Pathway
The Journal of biological chemistry, 2012Co-Authors: M Osanai-futahashi, K-i Tatematsu, J Narukawa, T Kayukawa, T Shinoda, T Tamura, Kimiko Yamamoto, Keiro Uchino, Yutaka Banno, Hideki SezutsuAbstract:Ommochromes are one of the major pigments involved in coloration of eggs, eyes, and body surface of insects. However, the molecular mechanisms of the final steps of Ommochrome pigment synthesis have been largely unknown. The eggs of the silkworm Bombyx mori contain a mixture of Ommochrome pigments, and exhibit a brownish lilac color. The recessive homozygous of egg and eye color mutant, red egg (re), whose eggs display a pale orange color instead of normal dark coloration, has been long suggested to have a defect in the biosynthesis of the final Ommochrome pigments. Here, we identify the gene responsible for the re locus by positional cloning, mutant analysis, and RNAi experiments. In the re mutants, we found that a 541-bp transposable element is inserted into the ORF of BGIBMGA003497-1 (Bm-re) encoding a novel member of a major facilitator superfamily transporter, causing disruption of the splicing of exon 9, resulting in two aberrant transcripts with frameshifts yielding nonfunctional proteins lacking the C-terminal transmembrane domains. Bm-re function in pigmentation was confirmed by embryonic RNAi experiments. Homologs of the Bm-re gene were found in all insect genomes sequenced at present, except for 12 sequenced Drosophila genomes, which seemed to correlate with the previous studies that have demonstrated that eye Ommochrome composition is different from other insects in several Dipterans. Knockdown of the Bm-re homolog by RNAi in the red flour beetle Tribolium castaneum caused adult compound eye coloration defects, indicating a conserved role in Ommochrome pigment biosynthesis at least among holometabolous insects.
-
Positional cloning of silkworm white egg 2 (w‐2) locus shows functional conservation and diversification of ABC transporters for pigmentation in insects
Genes to cells : devoted to molecular & cellular mechanisms, 2011Co-Authors: K-i Tatematsu, J Narukawa, T Tamura, Kimiko Yamamoto, Keiro Uchino, Yutaka Banno, Tetsuya Iizuka, Susumu Katsuma, Toru Shimada, Hideki SezutsuAbstract:The white, scarlet and brown genes of Drosophila melanogaster encode three half-type ATP-binding cassette (ABC) transporters. In Drosophila, precursors of Ommochromes and pteridines are transported by White/Scarlet and White/Brown heterodimers, respectively. The white egg 2 (w-2) mutant of the silkworm, Bombyx mori, has white eggs and eyes because of lack of Ommochrome granules in the serosa and eyes. Here, we report that the silkworm w-2 locus encodes an ortholog of Drosophila scarlet. Our results indicate that Bombyx Scarlet forms a heterodimer with Bombyx White to transport Ommochrome precursors, suggesting that formation of a White/Scarlet heterodimer and its involvement in the transport of Ommochrome precursors are evolutionarily ancient and widely conserved traits in insects. Contrary to dipteran insects, white and scarlet were juxtaposed in a head-to-tail orientation in the silkworm genome, suggesting that the origin of white and scarlet was a tandem duplication of their ancestral transporter gene. In Bombyx, White is also essential for the transport of uric acid in larval epidermis. However, our results suggest that a Bombyx White/Scarlet heterodimer is not involved in this process. Our results emphasize the functional conservation and diversification of half-type ABC transporter families in insects, which may contribute to their extremely diverse color patterns.
-
A single-base deletion in an ABC transporter gene causes white eyes, white eggs, and translucent larval skin in the silkworm w-3oe mutant
Insect biochemistry and molecular biology, 2008Co-Authors: Natuo Kômoto, Hideki Sezutsu, Guo-xing Quan, T TamuraAbstract:The w-3(oe) silkworm mutant has white eyes and eggs due to the absence of Ommochrome pigments in the eye pigment cells and serosa cells. The mutant is also characterized by translucent larval skin resulting from a deficiency in the transportation of uric acid, which acts as a white pigment in larval epidermal cells. A silkworm homolog of the fruitfly white gene, Bmwh3, a member of ATP-binding cassette transporter superfamily, was mapped on the w-3 locus. The w-3(oe) mutant has a single-base deletion in exon 2 and a premature stop codon at the 5' end of exon 3. These results show that w-3 is equivalent to Bmwh3 and is responsible for the transportation of Ommochrome precursors and uric acid into pigment granules and urate granules, respectively.
