Vestigial Wings Research Articles

Identification and characterization of the fusion transcript, composed of the apterous homolog and a putative protein phosphatase gene, generated by 1.5-Mb interstitial deletion in the vestigial ( Vg) mutant of Bombyx mori

The vestigial ( Vg) mutant is a Z-linked mutant that causes vestigial wings in the silkworm, Bombyx mori. We have previously reported a 1.5-Mb interstitial deletion on the Z chromosome bearing the Vg mutation (Z Vg chromosome). In this study, we found that exons 3–8 of a gene named Bmptp-Z encoding a putative tyrosine-specific protein phosphatase are deleted by the 1.5-Mb interstitial deletion. We found that a gene encoding the Bombyx homolog of Drosophila Apterous ( BmAp-A) protein is located 4.5 kb downstream of the distal breakpoint of the 1.5-Mb interstitial deletion. Moreover, an in-frame fusion transcript composed of the 5′ part of Bmptp-Z and the 3′ part of Bmap-A is generated specific to the Z Vg chromosome. Effects of the in-frame fusion transcript on the vestigial phenotype are discussed.

Wing shape differentiation of Mepraia species (Hemiptera: Reduviidae)

Mepraia is an endemic genus found in the semiarid and arid regions of north-central Chile. Until 1998, Mepraia spinolai was the only species of the genus, distributed in coastal and interior valleys from Chile between 18° and 34°S. However, on the basis of karyotype and morphological characters, coastal desert populations between 18° and 26°S were ranked as a new species, Mepraia gajardoi. Recently, genetic studies using nuclear and mitochondrial markers on Mepraia populations suggest that the geographical criterion to separate the two species should be reviewed. Mepraia species show conspicuous alary polymorphism, unique in the Triatominae subfamily. Females of both species are invariably micropterous, while males of M. spinolai can be micropterous, brachypterous or macropterous, and only brachypterous in M. gajardoi. In this study, we use geometric morphometrics analyses to compare male wings of M. spinolai and M. gajardoi from natural populations, in order to examine if these two species have diverged in alary shape. As expected, we found that brachypterous wings of both species are smaller than macropterous wings of M. spinolai. Additionally, we detected clear differences in shape on wings of M. gajardoi and M. spinolai, not attributable to allometric effects. For last, a new alary phenotype, insects with vestigial wings, was described here for the first time. In conclusion, our analyses on wings of Mepraia species separate two distinct groups consistent with the two described species. However, our findings of vestigial wings in some coastal areas of the north part of Chile cannot rule out the existence of a hybrid zone.

Correlations between spatiotemporal changes in gene expression and apoptosis underlie wing polyphenism in the ant Pheidole morrisi

Wing polyphenism, which is the ability of a single genome to produce winged and wingless castes in a colony in response to environmental cues, evolved just once and is a universal feature of ants. The gene network underlying wing polyphenism, however, is conserved in the winged castes of different ant species, but is interrupted at different points in the network in the wingless castes of these species. We previously constructed a mathematical model, which predicts that a key gene brinker (brk) mediates the development and evolution of these different "interruption points" in wingless castes of different ant species. According to this model, brk is upregulated throughout the vestigial wing discs of wingless ant castes to reduce growth and induce apoptosis. Here, we tested these predictions by examining the expression of brk, as well as three other genes up- and downstream of brk-decapentaplegic (dpp), spalt (sal), and engrailed (en)-in the winged reproductive and wingless soldier castes in the ant Pheidole morrisi. We show that expression of these genes is conserved in the wing disc of winged castes. Surprisingly, however, we found that brk expression is absent throughout development of the vestigial soldier forewing disc. This absence is correlated with abnormal growth of the soldier forewing disc as revealed by En expression and morphometric analyses. We also discovered that dpp and sal expression change dynamically during the transition from larval-to-prepupal development, and is spatiotemporally correlated with the induction of apoptosis in soldier forewing disc. Our results suggest that, contrary to our predictions, brk may not be a key gene in the network for suppressing wings in soldiers, and its absence may function to disrupt the normal growth of the soldier forewing disc. Furthermore, the dynamic changes in network interruptions we discovered may be important for the induction of apoptosis, and may be a general feature of gene networks that underlie polyphenism.

Revision of the New Zealand species of Mecyclothorax Sharp (Coleoptera: Carabidae: Psydrinae, Mecyclothoracini) and the consequent removal of several species to Meonochilus gen. n. (Psydrinae, Meonini)

The member taxa of Mecyclothorax Sharp, 1903 resident in New Zealand are redefi ned in light of diagnostic characters for the genus, necessitating description of Meonochilus, gen. n. to accommodate several species-level taxa previously combined with Mecyclothorax. Meonochilus is shown to be a member taxon of the tribe Meonini, a constituent along with Mecyclothoracini, of the subfamily Psydrinae. Meonochilus, gen. n. is diagnosed, and Tarastethus amplipennis Broun designated type species. Based on study of Phacothorax fleutiauxi Jeannel from New Caledonia, Phacothorax Jeannel, 1944 is newly synonymised with Mecyclothorax Sharp. The newly redefi ned Mecyclothorax fauna of New Zealand includes the widespread New Zealand native species M. rotundicollis (White), plus two geographically restricted endemic species; M. otagoensis, sp. n. from Central Otago, and M. oopteroides, sp. n. from the Chatham Islands. Mecylothorax ambiguus (Erichson), a species introduced from Australia, constitutes the fourth generic representative in New Zealand. Mecyclothorax otagoensis and M. oopteroides are synapomorphic for: 1, vestigial metathoracic flight wings; 2, a lightly sclerotised, spicule-covered dorsal plate associated with the male aedeagal internal sac; and 3, an apical crease on the male aedeagal median lobe. The shared absence of fl ight wings implies that the ancestral Chatham Islands' population was also characterised by brachyptery. Regarding genitalic evolution, though the male genitalia of these two species are essentially identical, the female reproductive tract in M. oopteroides has undergone dramatic evolution involving bifurcation of the bursa copulatrix. This evolutionary pattern is not consistent with any previous hypothesis of sexually selected genitalic evolution, leading to the conclusion that the bilobed bursal structure may have evolved in association with a different function, such as oviposition.

The developmental process during metamorphosis that results in wing reduction in females of three species of wingless-legged bagworm moths, Taleporia trichopterella, Bacotia sakabei and Proutia sp. (Lepidoptera: Psychidae)

There are several evolutionary grades of wing reduction in female bagworm moths of the family Psychidae. In this family, female adults of Taleporia trichopterella, Bacotia sakabei and Proutia sp. have vestigial wings, although as pupae they have small wings. Consequently, these species (usually called wingless-legged bagworm moths), are intermediate between the two extremes of females with normal wings and those with no wings. Using light and electron microscopy, the processes of wing development during the last-larval instar and wing degeneration during the pupal stage was investigated in these species. Female wing imaginal discs proliferated during the last-larval instar, but diminished due to apoptosis in the prepupal stage of the last instar. In the pupal stage, degenerate cells were observed between the epithelia of the degenerating wing discs of the female. The presence of these cells is associated with apoptotic cell death. These observations suggest that female-specific wing degeneration caused by apoptosis occurs in two steps in these bagworm moths, i.e. in the larval and pupal stages. Such a process of wing reduction has not been previously reported in holometabolous insects, and is reported here for the first time in bagworm moths.

Growth and patterning are evolutionarily dissociated in the vestigial wing discs of workers of the red imported fire ant, Solenopsis Invicta

Over the last decade, it has become clear that organismal form is largely determined by developmental and evolutionary changes in the growth and pattern formation of tissues. Yet, there is little known about how these two integrated processes respond to environmental cues or how they evolve relative to one another. Here, we present the discovery of vestigial wing imaginal discs in worker larvae of the red imported fire ant, Solenopsis invicta. These vestigial wing discs are present in all worker larvae, which is uncommon for a species with a large worker size distribution. Furthermore, the growth trajectory of these vestigial discs is distinct from all of the ant species examined to date because they grow at a rate slower than the leg discs. We predicted that the growth trajectory of the vestigial wing discs would be mirrored by evolutionary changes in their patterning. We tested this prediction by examining the expression of three patterning genes, extradenticle, ultrabithorax, and engrailed, known to underlie the wing polyphenism in ants. Surprisingly, the expression patterns of these three genes in the vestigial wing discs was the same as those found in ant species with different worker size distributions and wing disc growth than fire ants. We conclude that growth and patterning are evolutionarily dissociated in the vestigial wing discs of S. invicta because patterning in these discs is conserved, whereas their growth trajectories are not. The evolutionary dissociation of growth and patterning may be an important feature of gene networks that underlie polyphenic traits.

Systematics and biology of the endemic water scavenger beetles of Hawaii (Coleoptera: Hydrophilidae, Hydrophilini)

Abstract Recent field surveys in the Hawaiian Islands have revealed an adaptive radiation of endemic water scavenger beetles (Coleoptera: Hydrophilidae). Phylogenetic analysis based on 55 adult morphological characters affirms that this endemic hydrophilid fauna is a monophyletic clade that incorporates the first well-supported transformation from an aquatic to terrestrial way of life within any lineage of the subfamily Hydrophilinae. The clade is prescribed to the genus Limnoxenus Motschulsky, where described members were previously placed. Five new species are described: L. waialeale sp.n. (Kauai), L. kauaiensis sp.n. (Kauai), L. oahuensis sp.n. (Oahu), L. punctatostriatus sp.n. (Kauai) and L. namolokama sp.n. (Kauai). Lectotypes are designated for the two previously described species L. semicylindricus (Eschscholtz) and L. nesiticus (Sharp). The Hawaiian lineage is a component of a larger clade that also includes the remaining four species of Limnoxenus from Europe, South Africa, and Australia, plus the monotypic genera Limnocyclus Balfour-Browne of New Caledonia and Hydramara Knisch of South America. The majority of the Hawaiian species exhibit vestigial wings, an extremely unusual condition in aquatic beetles. No other island-endemic members of the Hydrophilinae are known to be flightless, suggesting insularity per se is not responsible for this condition. L. nesiticus of Oahu has not been collected during the past 106 years, suggesting that it has been lost to anthropogenically mediated extinction.

Modulation of the ecdysteroid‐induced cell death by juvenile hormone during pupal wing development of Lepidoptera

Females of the tussock moth Orgyia recens have only vestigial wings, whereas the males have normal wings. We previously found that ecdysteroid induces both apoptotic events and phagocytotic activation in sex-specific and region-specific manners. To investigate whether different responses to ecdysteroid are controlled at the receptor level, we cloned ecdysteroid receptor isoforms, EcR-A and EcR-B1, in O. recens. In both male and female wings, EcR-A signal was detected in the distal region of the bordering lacuna (BL), whereas EcR-B1 signal was detected in the proximal region of the BL. The similar expression patterns of both EcR isoforms suggested that molecules other than EcR should be involved in different ecdysteroid responses between male and female of O. recens. We next tested juvenile hormone (JH) effects on pupal wing morphogenesis in O. recens. Interestingly, both JH and 20E addition induced wing degeneration not only in females but also in males. In addition, higher concentration of JH pre-treatment of the pupal wings of the silkworm, Bombyx mori, also caused wing degeneration under ecdysteroid treatment. These results indicate that JH modulates the ecdysteroid action to induce the cell death on pupal wings, generally in Lepidoptera.

The costae presenting in high-temperature-induced vestigial wings of Drosophila: implications for anterior wing margin formation

It has long been noted that high temperature produces great variation in wing forms of the vestigial mutant of Drosophila. Most of the wings have defects in the wing blade and partially formed wing margin, which are the result of autonomous cell death in the presumptive wing blade or costal region of the wing disc. The vestigial gene (vg) and the interaction of Vg protein with other gene products are well understood. With this biochemical knowledge, reinvestigations of the high-temperature-induced vestigial wings and the elucidation of the molecular mechanism underlying the large-scale variation of the wing forms may provide insight into further understanding of development of the wing of Drosophila. As a first step of such explorations, I examined high-temperature-induced (29 degrees C) vestigial wings. In the first part of this paper, I provide evidences to show that the proximal and distal costae in these wings exhibit regular and continuous variation, which suggests different developmental processes for the proximal and distal costal sections. Judging by the costae presenting in the anterior wing margin, I propose that the proximal and distal costal sections are independent growth units. The genes that regulate formation of the distal costal section also strongly affect proliferation of cells nearby; however, the same phenomenon has not been found in the proximal costal section. The distal costal section seems to be an extension of the radius vein. vestigial, one of the most intensely researched temperature-sensitive mutations, is a good candidate for the study of marginal vein formation. In the second part of the paper, I regroup the wing forms of these wings, chiefly by comparison of venation among these wings, and try to elucidate the variation of the wing forms according to the results of previous work and the conclusions reached in the first part of this paper, and provide clues for further researches.

Morphological variations in the pre‐imaginal development of the ponerine antDiacamma ceylonense

AbstractIn the present paper, the larval development of the queenless ponerine antDiacamma ceylonenseis studied. Four instars were identified on the basis of cuticular processes – tubercles and spinules – which show discontinuous variation during growth and provide precise and reliable external morphological criteria for instar discrimination. In the first three instars, the larva possesses a striking proboscis, which disappears between the third and fourth instars. Larval weight increased around 50‐fold in the 21 days of larval life between eclosion and pupation (mean weight for first instar = 0.37 mg; for fourth instar = 20 mg). In addition, the morphology of the gemmae, structures resembling vestigial wings in workers, is described in nymphae.

Female-specific wing degeneration caused by ecdysteroid in the Tussock Moth, Orgyia recens: Hormonal and developmental regulation of sexual dimorphism

Females of the tussock moth Orgyia recens have vestigial wings, whereas the males have normal wings. During early pupal development, female wings degenerate drastically compared with those of males. To examine whether ecdysteroid is involved in this sex-specific wing development, we cultured pupal wings just after pupation with ecdysteroid (20-hydroxyecdysone, 20E). In the presence of 20E, the female wings degenerated to about one-fifth their original size. In contrast, the male wings cultured with 20E showed only peripheral degeneration just outside the bordering lacuna, as in other butterflies and moths. TUNEL analysis showed that apoptotic signals were induced by 20E over the entire region of female wings, but only in the peripheral region of male wings. Semi-thin sections of the wings cultured with ecdysteroid showed that phagocytotic hemocytes were observed abundantly throughout the female wings, but in only peripheral regions of male wings. These observations indicate that both apoptotic events and phagocytotic activation are triggered by ecdysteroid, in sex-specific and region-specific manners.

Female-specific wing degeneration caused by ecdysteroid in the Tussock Moth, Orgyia recens: Hormonal and developmental regulation of sexual dimorphism

Females of the tussock moth Orgyia recens have vestigial wings, whereas the males have normal wings. During early pupal development, female wings degenerate drastically compared with those of males. To examine whether ecdysteroid is involved in this sex-specific wing development, we cultured pupal wings just after pupation with ecdysteroid (20-hydroxyecdysone, 20E). In the presence of 20E, the female wings degenerated to about one-fifth their original size. In contrast, the male wings cultured with 20E showed only peripheral degeneration just outside the bordering lacuna, as in other butterflies and moths. TUNEL analysis showed that apoptotic signals were induced by 20E over the entire region of female wings, but only in the peripheral region of male wings. Semi-thin sections of the wings cultured with ecdysteroid showed that phagocytotic hemocytes were observed abundantly throughout the female wings, but in only peripheral regions of male wings. These observations indicate that both apoptotic events and phagocytotic activation are triggered by ecdysteroid, in sex-specific and region-specific manners.

Fleshing Out the Maelstrom

Fleshing Out the Maelstrom

Generic Evaluation of Boleum, Euzomodendron, and Vella (Brassicaceae)

Morphological, cytological, and molecular data support reduction of Boleum Desvaux and Euzomodendron Cosson to synonymy of Vella L. The new combination Vella bourgaeana is proposed. A key to species of Vella is presented. Boleum and Euzomodendron have generally been recognized as monotypic Spanish genera, and B. asperum (Persoon) Desvaux was originally described as Vella aspera Persoon. on other hand, includes five species distributed in Spain, Morocco, and Algeria. In his comprehensive revision of tribe Brassiceae, Schulz (1923) placed Boleum, Carrichtera DC., Psychine Desfontaines, Rytidocarpus Cosson (as Distomocarpus O. E. Schulz), Schouwia DC., and Succowia Medikus in subtribe Vellinae, and placed Euzomodendron, Savignya DC., and Oudneya R. Brown in subtribe Savignyinae. Schulz (1919, 1936) separated these subtribes primarily on basis of presence vs. absence of median nectar glands and seed wing: Vellinae have median glands and lack seed wing, whereas Savignyinae lack median nectar glands and have seed wing. G6mez-Campo (1978), however, indicated presence of vestigial wings in Boleum and Vella and suggested that Euzomodendron should be placed with these two genera in one group. He also suggested (G6mez-Campo, 1980) that Savignyinae be united with Vellinae. Except for shape of valvular segment and presence of a well-developed seed wing, Euzomodendron resembles Vella and Boleum in almost all other morphological characters, especially woody habit, connation of inner filaments in pairs, and presence of short pedicels, saccate lateral sepals, long petal claws, dark-veined petal blades, seedless flattened beaks, strongly 3or 5-veined valves, and acutely notched cotyledons (Table 1). In fact, G6mez-Campo (1978) indicated that the robust valves [of Euzomodendron] with narrowed base resemble that of Vella, and G6mez-Campo and Tortosa (1974) showed that cotyledonary notch is indistinguishable in three genera. However, not only did recent floristic accounts (e.g., G6m z-Campo, 1993; L6pez-Gonzilez, 1993; Marcos-Samaniego, 1993; Heywood, 1993) maintain three genera but also placed Euzomodendron remotely from Boleum and Vella. These three genera have been maintained historically because of taxonomic value placed on fruit length, fruit dehiscence, and seed wing. In our opinion, overwhelming similarities in all other characters have been either ignored or given insufficient weight. The connation of inner filaments into pairs in Euzomodendron, Boleum, and Vella is a remarkable synapomorphy not found elsewhere in tribe Brassiceae. Several large genera (e.g., Draba L., Arabis L., and Erysimum L.), and even a smaller one such as Lobularia Desvaux (4 spp.; Borgen, 1987), include taxa with winged or wingless seeds, whereas Draba, Rorippa Scopoli, and Leavenworthia Torrey, to name just a few, include species with both globose and narrowly oblong to linear fruits (for many examples, see Rollins, 1993). Therefore, fruit shape and presence of seed wing often do not warrant delimitation of genera, especially when used alone. The similarities between Boleum and Vella are even stronger than between these and Euzomodendron. The most reliable characters used to separate first two are presence in Boleum of short-pedicellate, indehiscent, sessile fruits, and in Vella of slightly longer-pedicelled, dehiscent, gynophorate or sessile fruits (Table 1). These characters do not justify maintenance of these genera. In fact, dehiscent and indehiscent fruits can be found within Tetracme Bunge, Coronopus Zinn, Sterigmostemum M. Bieberstein, and Ornithocarpa Rose (or even on same plant, as in Diptychocarpus strictus (DC.) Trautvetter, Cardamine chenNovoN 8: 321-325. 1998. This content downloaded from 207.46.13.92 on Wed, 30 Nov 2016 05:02:58 UTC All use subject to http://about.jstor.org/terms

Alterations in free radical activity in aging Drosophila

Drosophila were examined to see if there is an increase in damage associated with free radical activity in older flies. The levels of superoxide radical and of lipid peroxides were higher in membrane samples from older flies. Also, in older Drosophila there was a significant decrease in membrane fluidity, as determined by fluorescence polarization, and an increase in ATP-dependant calcium uptake. In homogenates from whole flies, the concentration of inorganic peroxides and activity of the proteolytic enzyme, cathepsin B, increased with age. During their lifetime, vestigial wing Drospphila displayed a greater level of free radical activity than wild-type flies and a significantly shorter life span (26.7 ± 0.7 days vs. 34.4 ± 1.0, p < 0.01). These results indicate that the level of oxidative stress is closely coupled to cellular damage and to life span, and they indicate that free radicals may play a central role in the aging process in Drosophila.

The effects of ambient temperature on life span, lipid peroxidation, superoxide dismutase, and phospholipase A 2 activity in Drosophila melanogaster

Aging changes were examined in Drosophila melanogaster. Lifespan was determined in two strains of male and female Drosophila raised at 19°, 24°, and 29° C. The results show an inverse relationship between lifespan and temperature. In addition, lipid peroxidation rates and superoxide dismutase activity were measured in homogenates and phospholipase A 2 activity was determined in crude membrane samples prepared from this species. Temperature was found to be directly correlated with the rate of lipid peroxidation in each group. The longest-lived group, wild-type females, exhibited the lowest rate of lipid peroxidation at each temperature; whereas the shortest-lived group, vestigial wing males, displayed the highest rates of lipid peroxidation. Older (40–53 day) vestigial wing males also exhibited significantly higher superoxide dismutase activity than younger vestigial wing males (0–5 day) and higher phospholipase A 2 activity than wild-type females of the same age. These results indicate that there is an association between lipid peroxidation rates and lifespan in Drosophila, and that aging changes may include an increase in superoxide dismutase and phospholipase A 2 activity. These findings agree with the hypothesis that free radicals are involved in the aging process in Drosophila.

Gamma Irradiation as a Quarantine Treatment for Cherries Infested by Western Cherry Fruit Fly (Diptera: Tephritidae)1

Western cherry fruit fly (WCFF), Rhagoletis indifferens Curran, infests cherries in the northwestern United States. Exposure of naturally infested fruit to doses from 42 to 210 Gray (Gy) reduced pupation; only one adult emerged (at 127 Gy). In a second test in which fruit were exposed to from 4.4 to 106 Gy, no adults emerged following irradiation of field-infested fruit at ≥17.6 Gy. When > 124,000 naturally infested cherries were exposed to 97 Gy, gamma irradiation was an efficacious quarantine treatment. No normal adults and only one abnormal adult with vestigial wings emerged from a treated population estimated to be 84,369 WCFF larvae. This research demonstrated that irradiation would be a potential quarantine treatment for WCFF larvae in cherries. Parasites, Pachycrepoideus vindemiae (Rondani), emerged from many of the untreated puparia but not from those WCFF irradiated as larvae.

Presynaptic terminals persist following degeneration of "flight" muscle during development of a flightless grasshopper.

We have studied the development of a neuromuscular system for which mature function has been lost through evolution in the grasshopper, Barytettix psolus (Cohn and Cantrall, 1974). Barytettix is flightless throughout life and has only vestigial wings that are incapable of active movement. Adult Barytettix lack muscles homologous to the indirect flight muscles of locusts and grasshoppers that fly, while other thoracic muscles are similar. We have found, using light and electron microscopic examination of tissues from various developmental stages, that the metathoracic dorsal longitudinal muscle is present and is innervated during nymphal life but is absent in adults. Yet its nerve persists and, in the adult, contains axonal presynaptic specializations opposite inappropriate targets such as glial processes and basal lamina. Our findings indicate that selective muscle death during development is one mechanism underlying the reduction of the flight system of Barytettix through evolution. The finding that presynaptic terminals persist in the absence of the muscle indicates that the muscle and its innervation follow programs of development that are at least partially independent and reinforces the concept that in insects motorneurons, and perhaps neurons in general, are not dependent upon trophic influences from their targets for survival and maintenance of their differentiated phenotype.

Age-related DNA fragmentation in two varieties of Drosophila melanogaster, phaseolus (cotyledons), and three tissues of the mouse

Agarose gel electrophoresis showed that no age-related DNA fragmentation occured in wild-type or vestigial wing Drosophila, or in DNA from mouse brain and heart. DNA from mouse liver possessed a large fragment, estimated at 24 megadaltons, in all ages tested. Phaseolus cotyledon DNA possessed a fragment of approximately 3.5 megadaltons in both imbided seeds and 12-day-old cotyledons. Thus, there appeared to be no age-related increase in the break-down of DNA into large fragments.

Regulative Properties of Wing Discs from the Vestigial Mutant of Drosophila melanogaster

The vestigial (vg) mutant of Drosophila melanogaster shows reduced wing size and lacks margin structures from the wing blade. The expressivity is temperature-sensitive, more structures being formed at 29°C than at 25°C. There is cell death in the third instar wing disc which to some extent parallels the fate map locations of the structures absent in the adult. Vestigial wing discs are unable to regenerate margin structures even when given extra time for growth by culturing them in an adult abdomen before metamorphosis. If the region of cell death is excised from the disc before culture, there is still no regeneration of margin structures, indicating that the dead cells do not physically prevent regulation. Furthermore, by metamorphosing young vg wing discs, it was discovered that cells never acquire competence to make margin during wing disc development. Experiments mixing fragments of vg wing disc with non-vg wing disc fragments of ebony multiple wing hairs (e mwh) genotype showed that the vg cells interacted with the e mwh cells and wing blade was intercalated of both genotypes. However, structures such as wing margin, and alar lobe, usually affected in vg wings, were always made from e mwh cells and not from vg cells. Analysis of mutants which are unable to differentiate particular cell types may help us to understand the mechanism of pattern establishment in developing imaginal discs.