Eye Color Mutants Research Articles

Longevity of africanized worker honey bees (Apis mellifera) carrying eye color mutant alleles

The dark coloration of insects eyes is attributed to the accumulation of the brown pigment insectorubin, a mixture of ommochromes, xanthommatin and several ommins, biosynthesized from tryptophan. When any of the events in the synthesis chain is interrupted, formation and accumulation of pigments other than insectorubin occurs, and a new eye color will appear. The aim of the present work is to evaluate the longevity of worker honey bees Apis mellifera, homozygous and heterozygous for the mutant alleles cream (cr), snow-laranja (s la) and brick (bk). Eye pigmentation and average longetivity of bees are very closely related. Mutant bees carrying lighter eye pigmentation are unable to return to the hive; there is, therefore, a close association between the eye pigmentation and honey bees lifespan. Experiments ran in confinement cages confirm the orientation problems of mutant honey bees, which kept in a limited space, were able to return to the hive and had an extended lifespan in comparison to that observed in the nature, and did not present statistical difference (P>0.05) relative to the control group. Confinement to restricted areas improves honey bees orientation abilities and facilitates return to the hive.

Cloning and characterization of the Tribolium castaneum eye-color genes encoding tryptophan oxygenase and kynurenine 3-monooxygenase.

The use of eye-color mutants and their corresponding genes as scorable marker systems has facilitated the development of transformation technology in Drosophila and other insects. In the red flour beetle, Tribolium castaneum, the only currently available system for germline transformation employs the exogenous marker gene, EGFP, driven by an eye-specific promoter. To exploit the advantages offered by eye-pigmentation markers, we decided to develop a transformant selection system for Tribolium on the basis of mutant rescue. The Tribolium orthologs of the Drosophila eye-color genes vermilion (tryptophan oxygenase) and cinnabar (kynurenine 3-monooxygenase) were cloned and characterized. Conceptual translations of Tc vermilion (Tcv) and Tc cinnabar (Tccn) are 71 and 51% identical to their respective Drosophila orthologs. We used RNA interference (RNAi) to show that T. castaneum larvae lacking functional Tcv or Tccn gene products also lack the pigmented eyespots observed in wild-type larvae. Five available eye-color mutations were tested for linkage to Tcv or Tccn via recombinational mapping. No linkage was found between candidate mutations and Tccn. However, tight linkage was found between Tcv and the white-eye mutation white, here renamed vermilion(white) (v(w)). Molecular analysis indicates that 80% of the Tcv coding region is deleted in v(w) beetles. These observations suggest that the Tribolium eye is pigmented only by ommochromes, not pteridines, and indicate that Tcv is potentially useful as a germline transformation marker.

<I>Rose</I>, an Eye Color Mutation in a Species of the <I>Anastrepha fraterculus</I> Complex (Diptera: Tephritidae)

Abstract The rose eye color mutation is described in Anastrepha sp.1 aff. fraterculus. It changes the color of the wild-type eyes from reddish with a blue-green iridescence to yellow-orange with a rosy iridescence. The wild-type and rose phenotypes are distinguishable in dried individuals at least 2–3 wk after death. Rose is transmitted as a recessive autosomal mutation. Disruption of the ommatidial pattern was observed as an alignment irregularity and enlargement of some individual ommatidia. Mutant individuals have reduced fitness relative to the wild-type. The rose mutation, the first one described in Anastrepha, has potential use in release-recapture studies and as a marker for mass-reared flies.

Red-eye mutants in Orius bugs (Heteroptera: Anthocoridae).

Eye-color mutants were found in the flower bugs, Orius sauteri (Poppius) and O. strigicollis (Poppius), which are effective natural enemies of thrips and mites. The mutants have bright red eyes, and are easily discriminated from the wild type (with purple to black eyes) after the 2nd nymphal instar. By crossing experiments, it was determined that the red eye trait was recessive and the locus was inferred to be autosomal in both species. In experiments using the mutants, it was shown that Orius sauteri and O. strigicollis females mate only once or a few times during their lifetimes. Similar mutants may be found in other Orius populations or species.

Identification and characterisation of a silkworm ABC transporter gene homologous to Drosophila white.

In the silkworm, Bombyx mori, many eye- and egg-colour mutations affecting the synthesis and accumulation of ommochrome pigments have been described. In order to understand the pigment precursor transporters involved, ABC transporter genes homologous to the Drosophila white gene were isolated from the silkworm. Reverse transcriptase-polymerase chain reactions (RT-PCR) using embryonic mRNA amplified three cDNA fragments, named Bmwh1, Bmwh2 and Bmwh3 that showed homology to the white gene. Since Bmwh3 shows the highest degree of sequence identity and a similar expression pattern to the Drosophila homologue, we characterised this gene further. A 2667-bp Bmwh3 cDNA isolated from an embryonic library has one ORF encoding a polypeptide of 687 amino acids. The predicted protein has one ATP-binding domain, six transmembrane-spanning segments and high similarity to the Drosophila WHITE protein. Southern analysis indicates that Bmwh3 is a single-copy gene. Polyadenylated Bmwh3 transcripts about 2.7 kb long were detected in eggs, Malpighian tubules and pupal heads, but not in testes, posterior silk glands or fat body cells. The level of Bmwh3 mRNA was reduced in w3 and w3ol mutants but normal in other egg- and eye-colour mutants, suggesting that Bmwh3 correspond to the w3 locus. Genetic analysis was used to map the cloned gene to chromosome 10.

Defective pigment granule biogenesis and aberrant behavior caused by mutations in the Drosophila AP-3beta adaptin gene ruby.

Lysosomal protein trafficking is a fundamental process conserved from yeast to humans. This conservation extends to lysosome-like organelles such as mammalian melanosomes and insect eye pigment granules. Recently, eye and coat color mutations in mouse (mocha and pearl) and Drosophila (garnet and carmine) were shown to affect subunits of the heterotetrameric adaptor protein complex AP-3 involved in vesicle trafficking. Here we demonstrate that the Drosophila eye color mutant ruby is defective in the AP-3beta subunit gene. ruby expression was found in retinal pigment and photoreceptor cells and in the developing central nervous system. ruby mutations lead to a decreased number and altered size of pigment granules in various cell types in and adjacent to the retina. Humans with lesions in the related AP-3betaA gene suffer from Hermansky-Pudlak syndrome, which is caused by defects in a number of lysosome-related organelles. Hermansky-Pudlak patients have a reduced skin pigmentation and suffer from internal bleeding, pulmonary fibrosis, and visual system malfunction. The Drosophila AP-3beta adaptin also appears to be involved in processes other than eye pigment granule biogenesis because all ruby allele combinations tested exhibited defective behavior in a visual fixation paradigm.

Changes in the structure and pigmentation of the eyes of honeybee (Apis mellifera L.) queens with the "limão" mutation

This study describes the ultrastructural differences between the compound eyes of ch li/ch li and Ch/ch li honeybee queens. Heterozygous "limão" bees had an almost normal ultrastructural organization of the ommatidia, but there were some alterations, including small vacuoles in the crystalline cones and a loss of pigment by primary pigmentary cells. In homozygous bees many ommatidia had very deformed crystalline cones and there were some bipartite rhabdoma. There was a reduction in the amount of pigment in the primary and secondary pigmentary cells and receptor cells (retinulae) of mutant eyes. However, the eyes of both heterozygous and homozygous queens had the same type of pigment granules. Certain membrane-limited structures containing pigment granules and electron-dense material appeared to be of lysosomal nature. Since these structures occurred in the retinular cells of mutant eyes, they were considered to be multivesicular bodies responsible for the reduction in rhabdom volume in the presence of light, as a type of adaptation to brightness. The reduction of pigment in the pigmentary and retinular cells and the morphological changes seen in the rhabdom of the ommatidia may originate visual deficiencies, which could explain the behavioral modifications reported for Apis mellifera queens with mutant eye color.

Mosaic: a position-effect variegation eye-color mutant in the mosquito Anopheles gambiae.

The Mosaic (Mos) mutation, isolated in the F1 of 60Co-irradiated mosquitoes, confers variegated eye color to third and fourth instar larvae, pupae, and adults of the mosquito Anopheles gambiae. Mos is recessive in wild pink eye (p+) individuals, but is dominant and confers areas of wild-type pigment in mutant pink eye backgrounds. Mos is located 14.4 cM from pink eye on the X chromosome and is associated with a duplication of division 2B euchromatin that has been inserted into division 6 heterochromatin. Various combinations of Mos, pink eye alleles, and the autosomal mutation red eye were produced. In all cases, the darker pigmented regions of the eye in Mos individuals show the phenotypic interactions expected if the phenotype of those regions is due to expression of a p+ allele. Expression of Mos is suppressed by rearing larvae at 32 degrees C relative to 22 degrees C. All of these characteristics are consistent with Mos being a duplicated wild copy of the pink eye gene undergoing position-effect variegation.

Genetic and biochemical analysis of brown eye mutation in Drosophila nasuta nasuta and Drosophila nasuta albomicans.

By analyzing the progeny of crosses involving brown eye mutants and the wild types in two members of Drosophila nasuta subgroup namely D. n. nasuta and D. n. albomicans we could show that the mutant gene is recessive, located in the chromosome 2 and the alleles of this gene are present at different loci. A study of fitness in the eye color mutants in comparison with the wild types revealed that D. n. nasuta mutant has higher viability at both 25+/-1 degrees C and ambient temperatures; while D. n. albomicans mutant has faster rate of development only at 25+/-1 degrees C. Quantitative analysis of eye pigments in the mutants revealed that there is biosynthesis of both pteridines and xanthommatins unlike in bw/bw of D. melanogaster, where only xanthommatins are synthesized. In both the species, the pteridine quantities in mutants are similar; whereas xanthommatin quantity in bw(n)/bw(n) is 10 times higher than that of bw(a)/bw(a). Further, the F1 progeny of intraspecific crosses (wild type X mutant) are found to have high amounts of pteridine, even when compared with parental wild type.

Transient expression of tryptophan oxygenase gene from Anopheles gambiae in the green eye mutant of the housefly, Musca domestica (Diptera: Muscadae).

A plasmid construct containing the gene encoding tryptophan oxygenase (to) from Anopheles gambiae was introduced into green eye color mutants (ge) of the housefly, Musca domestica. Several variations in eye color were observed in 38.8% of the surviving G0 adults. The expression of A. gambiae to in the distantly related Diptera, housefly, implies conservation of the tryptophan oxygenase gene in the other Diptera and may be used for monitoring transformants as a marker in insects which have mutants homologous to Drosophila melanogaster vermilion.

A Role for the deep orange and carnation Eye Color Genes in Lysosomal Delivery in Drosophila

deep orange and carnation are two of the classic eye color genes in Drosophila. Here, we demonstrate that Deep orange is part of a protein complex that localizes to endosomal compartments. A second component of this complex is Carnation, a homolog of Sec1p-like regulators of membrane fusion. Because complete loss of deep orange function is lethal, the role of this complex in intracellular trafficking was analyzed in deep orange mutant clones. Retinal cells devoid of deep orange function completely lacked pigmentation and exhibited exaggerated multivesicular structures. Furthermore, a defect in endocytic trafficking was visualized in developing photoreceptor cells. These results provide direct evidence that eye color mutations of the granule group also disrupt vesicular trafficking to lysosomes.

Brief communication. Genetics of creamish white, an eye color mutant in Anopheles stephensi

Genetic analysis of a new eye color mutant, creamish white (cw), has been described in Anopheles stephensi, a major vector of malaria in the Indo-Pakistan subcontinent. Inheritance pattern revealed that it is sex linked and recessive to wild eye color. Creamish white eye was found to be nonallelic and epistalic to another recessive, sex-linked mutant, red eye (r). The map distance between cw and r was estimated as 41.80 ± 0.99.

RBE-LET relationships of high-LET radiations in Drosophila mutations.

The relative biological effectiveness (RBE) of 252Cf neutrons and synchrotron-generated high-energy charged particles for mutation induction was evaluated as a function of linear energy transfer (LET), using the loss of heterozygosity for wing-hair mutations and the reversion of the mutant white-ivory eye-color in Drosophila melanogaster. Loss of heterozygosity for wing-hair mutations results predominantly from mitotic crossing over induced in wing anlage cells of larvae, while the reverse mutation of eye-color is due to an intragenic structural change (2.96 kb-DNA excision) in the white locus on the X-chromosome. The measurements were performed in a combined mutation assay system so that induced mutant wing-hair clones as well as revertant eye-color clone can be detected simultaneously in the same individual. Larvae were irradiated at the age of 3 days post oviposition with 252Cf neutrons, carbon beam or neon beam. For the neutron irradiation, the RBE values for wing-hair mutations were larger than that for eye-color mutation by about 7 fold. The RBE of carbon ions for producing the wing-hair mutations increased with increase in LET. The estimated RBE values were found to be in the range 2 to 6.5 for the wing-hair. For neon beam irradiation, the RBE values for wing-hair mutations peak near 150 keV/micron and decrease with further increase in LET. On the other hand, the RBE values for the induction of the eye-color mutation are nearly unity in 252Cf neutrons and both ions throughout the LET range irradiated. We discuss the relationships between the initial DNA damage and LET in considering the mechanism of somatic mutation induction.

Not just pretty eyes: Drosophila eye-colour mutations and lysosomal delivery

Analysis of Drosophila eye-colour mutations has made seminal contributions to the fields of genetics and biochemistry. Recent findings suggest that a subset of eye-colour genes is crucial for vesicular transport of proteins to pigment granules, specialized lysosomes of eye-pigment cells. Thus, classical work describing more than 85 eye-colour mutations and their genetic interactions offers a remarkable, untapped resource for the genetic analysis of protein delivery to lysosomes.

15] ABC transporters involved in transport of eye pigment precursors in Drosophila melanogaster

Publisher Summary The usual red-brown color of the eyes of the vinegar fly Drosophila melanogaster is because of the presence of two light-screening pigments: (1) xanthommatin, which is brown and (2) a class of pigments known as drosopterins, which are red. These pigments are deposited in membrane-bound granules in specialized pigment cells in each ommatidium of the compound eye. Xanthommatin is derived biosynthetically from tryptophan and drosopterins are derived from guanosine triphosphate (GTP). The chapter characterizes the genes and proteins involved in transport of the pigment precursor molecules from the haemolymph into the fly eye pigment cells. Studies of eye color mutant flies have revealed three genetic loci (white, brown, and scarlet) in which mutations do not alter levels of the enzymes involved in pigment biosynthesis, but instead interfere with the ability of cells to take up pigment precursors.

Egg deposition behavior in the haplodiploid sawfly Athalia rosae ruficornis Jakovlev (Hymenoptera: Symphyta: Tenthredinidae)

The egg deposition behavior of the turnip sawfly, Athalia rosae (Hymenoptera: Symphyta), is described. Both unmated and mated females lay eggs individually inside of fresh young leaves of cruciferous plants. During an oviposition event, females exhibit a distinct pause in abdominal contractions just before the actual egg deposition act. Unmated females show a longer pause (11.31 s on average) than mated females (4.38 s on overall average). By employing an eye color mutation, the sex of the eggs laid by females was ascertained. Females mated once lay mostly fertilized (diploid female) eggs initially but begin to lay a considerable number of unfertilized (haploid male) eggs later in life. The laying of an unfertilized egg is associated with a longer pause (6.98 s on average) than the laying of a fertilized egg (3.76 s on average). These results are in contrast to previous reports on apocritan Hymenoptera, where the presence of a pause or a longer pause during oviposition was associated with the deposition of fertilized eggs rather than unfertilized eggs. The possibility that mated Athalia rosae females control fertilization and its implications for sex allocation strategies are discussed.

The relative biological effectiveness of accelerated carbon ions with different LET for inducing mitotic crossing over and intragenic reversion of the white-ivory allele in Drosophila larvae

Purpose : To evaluate the relative biological effectiveness (RBE) of accelerated carbon ions generated with a synchrotron for inducing mutations as a function of linear energy transfer (LET), using the loss of heterozygosity for wing-hair mutations and the reversion of the mutant white-ivory eye-colour in Drosophila melanogaster. Materials and methods : The measurements were made using a combined mutation assay system so that induced mutant winghair clones as well as revertant eye-colour clones can be detected simultaneously in the same fly. Larvae were irradiated at the age of 72 6 h post-oviposition with X-rays or carbon ions with LET values of 13, 60 and 95 keV/ mu m. Results : The RBE of carbon ions for producing wing-hair mosaic spots increased with increasing LET values. The RBE for the induction of eye-colour mutants did not change with LET. The estimated RBE values were found to be in the range 2 to 6 5 for the wing-hair and nearly unity for the eye-colour mosaic spot mutations. Conclusions : RBE-LET relationships were obtained for the induction of wing-hair and eye-colour mosaic spots. These relationships suggest that more complex types of DNA damage, such as nonrejoinable strand breaks that increase with LET, may be responsible for inducing the wing-hair mutation, while more simple forms of molecular damage induce reversion in the white-ivory allele.

Suppressor genes with gender differences in activity in natural populations of Drosophila robusta: another approach to wild-type.

Homozygous or hemizygous expression of an X-linked wing mutant of Drosophila robusta varies from a rudimentary wing that does not reach the tip of the abdomen (called 'club') to forms with full-sized but curled or crumpled wings (called 'curly'). Homozygous club females crossed to flies from natural populations or laboratory stocks derived from wild flies invariably produce significantly less club male progeny than the 100% expected, most of them exhibiting less severe phenotypes: 'curly' forms and wild-type. The male progeny from similar crosses using curly females tend to be predominantly normal. By contrast, the male progeny of outcrossed females homozygous for an X-linked eye colour mutant, vermilion, are all vermilion. The data indicate that natural populations of D. robusta contain suppressors of the wing mutant but not of the eye colour mutant studied. Activity of the suppressors differs by gender: in experiments in which genetic theory expects similar results in the two sexes, males consistently show stronger effects of the suppressors than females.

New Allele at a Locus Affecting Developmental Time in Mediterranean Fruit Fly (Diptera: Tephritidae) and Its Potential Use in Genetic Sexing at the Egg Stage

The use of the chromosome 2 linked eye color mutation sw-z, which causes slow development during the larval and pupal stages, has been proposed as a way to separate males from females in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). But rearing costs could be greatly reduced if females were eliminated at an earlier stage. A 2nd mutation, sw-y , showing slow embryonic development compared with wild type has been isolated. We compared the duration of the embryonal, larval, and pupal stages at 2 different temperatures among the mutants and hybrids between them. The results showed that sw-y and sw-z are significantly slower in embryonic, larval, and pupal development than the wild-type control, with sw-y being the slowest. These differences are greater at low than at high temperature. The complementation test indicates that sw-z and sw-y are 2 alleles at the same locus. It is concluded that separation at the egg-larva transition will be possible with sw-y .

Inheritance patterns of new genetic markers and occurrence of spontaneous mosaicism in the monogenic blowfly Chrysomya rufifacies (Diptera:Calliphoridae).

Four new genetic markers for Chrysomya rufifacies, a fly with maternal sex determination, were characterized. The markers include one body colour mutant, black body (bl), and three eye colour mutants, brown eye (br), apricot eye (ap), and red eye (wr). Two of the latter, br and wr, turn out to be sex linked, the others behave as autosomal genes belonging to different linkage groups. wr is a hypomorphic and w an apomorphic mutation of the white gene, w/w is epistatic to br/br and to ap/ap. A preliminary genetic linkage map with the sex realizer F'/f and the loci br and w residing in homomorphic sex chromosomes is established. Evidence is presented that crossing over is absent in the male sex. The possible causes of the spontaneous appearance of mosaics for eye colour observed among individuals heterozygous for recessive genes are discussed.