Late Pupal Stage Research Articles

Synthesis and chemical composition of mucus gland secretions inApis cerana indica

The columnar epithelial cells of the mucus gland begin to synthesize secretory material in the late pupal stage, and this material gradually accumulates in the lumen, beginning soon after emergence of the adult drones. Histochemical tests demonstrated secretory activity in the epithelial cells and revealed the biochemical nature of the secretions as a mixture of proteins, carbohydrates and lipids. Total proteins, lipids and carbohydrates were detected in concentrations of 333.2 ± 13.883, 208.60 ± 11.69 and 44.82 ± 2.94 μg/mg, respectively, showing that proteins form the major constituents of the mucus gland secretory material. SDS-PAGE of mucus gland secretory material revealed about 15 proteins of molecular weight ranging from 2.5 to 151.2 kDa. Three proteins of 45, 43 and 37 kDa were stained intensely and can be considered as the major class of mucus proteins.

NinaB Is Essential for Drosophila Vision but Induces Retinal Degeneration in Opsin-deficient Photoreceptors

In animals, visual pigments are essential for photoreceptor function and survival. These G-protein-coupled receptors consist of a protein moiety (opsin) and a covalently bound 11-cis-retinylidene chromophore. The chromophore is derived from dietary carotenoids by oxidative cleavage and trans-to-cis isomerization of double bonds. In vertebrates, the necessary chemical transformations are catalyzed by two distinct but structurally related enzymes, the carotenoid oxygenase beta-carotenoid-15,15'-monooxygenase and the retinoid isomerase RPE65 (retinal pigment epithelium protein of 65 kDa). Recently, we provided biochemical evidence that these reactions in insects are catalyzed by a single enzyme family member named NinaB. Here we show that in the fly pathway, carotenoids are mandatory precursors of the chromophore. After chromophore formation, the retinoid-binding protein Pinta acts downstream of NinaB and is required to supply photoreceptors with chromophore. Like ninaE encoding the opsin, ninaB expression is eye-dependent and is activated as a downstream target of the eyeless/pax6 and sine oculis master control genes for eye development. The requirement for coordinated synthesis of chromophore and opsin is evidenced by analysis of ninaE mutants. Retinal degeneration in opsin-deficient photoreceptors is caused by the chromophore and can be prevented by restricting its supply as seen in an opsin and chromophore-deficient double mutant. Thus, our study identifies NinaB as a key component for visual pigment production and provides evidence that chromophore in opsin-deficient photoreceptors can elicit retinal degeneration.

Hormonal and nutritional regulation of insect fat body development and function

The insect fat body is an organ analogue to vertebrate adipose tissue and liver and functions as a major organ for nutrient storage and energy metabolism. Similar to other larval organs, fat body undergoes a developmental "remodeling" process during the period of insect metamorphosis, with the massive destruction of obsolete larval tissues by programmed cell death and the simultaneous growth and differentiation of adult tissues from small clusters of progenitor cells. Genetic ablation of Drosophila fat body cells during larval-pupal transition results in lethality at the late pupal stage and changes sizes of other larval organs indicating that fat body is the center for pupal development and adult formation. Fat body development and function are largely regulated by several hormonal (i.e. insulin and ecdysteroids) and nutritional signals, including oncogenes and tumor suppressors in these pathways. Combining silkworm physiology with fruitfly genetics might provide a valuable system to understand the mystery of hormonal regulation of insect fat body development and function.

Rectal sac distention is induced by 20-hydroxyecdysone in the pupa of Bombyx mori

Holometabolous insects do not excrete but store metabolic wastes during the pupal period. The waste is called meconium and is purged after adult emergence. Although the contents of meconium are well-studied, the developmental and physiological regulation of meconium accumulation is poorly understood. In Bombyx mori, meconium is accumulated in the rectal sac; thereby, the rectal sac distends at the late pupal stage. Here, we show that rectal sac distention occurs between 4 and 5 days after pupation. The distention is halted by brain-removal just after larval–pupal ecdysis but not by brain-removal 1 day after pupation. In the pupae, brain-removal just after ecdysis kept the hemolymph ecdysteroid titer low during early and mid-pupal stages. An injection of 20-hydroxyecdysone (20E) evoked the distention that was halted by brain-removal in a dose-dependent manner. Therefore, brain-removal caused the lack of ecdysteroid, and rectal sac distention did not appear in the brain-removed pupae because of the lack of ecdysteroid. We conclude that rectal sac distention is one of the developmental events regulated by 20E during the pupal period in B. mori.

The DHHC Palmitoyltransferase Approximated Regulates Fat Signaling and Dachs Localization and Activity

Signaling via the large protocadherin Fat (Ft), regulated in part by its binding partner Dachsous (Ds) and the Golgi-resident kinase Four-jointed (Fj), is required for a variety of developmental functions in Drosophila. Ft and, to a lesser extent, Ds suppress overgrowth of the imaginal discs from which appendages develop and regulate the Hippo pathway [1-5] (reviewed in [6]). Ft, Ds, and Fj are also required for normal planar cell polarity (PCP) in the wing, abdomen, and eye and for the normal patterning of appendages, including the spacing of crossveins in the wing and the segmentation of the leg tarsus (reviewed in [7-9]). Ft signaling was recently shown to be negatively regulated by the atypical myosin Dachs [10, 11]. We identify here an additional negative regulator of Ft signaling in growth control, PCP, and appendage patterning, the Approximated (App) protein. We show that App encodes a member of the DHHC family, responsible for the palmitoylation of selected cytoplasmic proteins, and provide evidence that App acts by controlling the normal subcellular localization and activity of Dachs.

Sex pheromones in three Bradysia species (Dipt., Sciaridae): novel bioassays with female body extracts and fractions

AbstractFemales of the fungus gnat species Bradysia difformis, Bradysia optata and Bradysia tilicola are able to produce sexual attractants. In males, the female extracts elicit species‐specific courtship behaviour and attraction in an olfactometer bioassay. Attractiveness of the sex pheromone extracts seems to differ in the investigated species, being highly attractive for males in B. difformis and only moderately attractive in B. tilicola. Female B. difformis are attractive from late pupal stages until death of the imago. In contrast, female B. optata and B. tilicola are not attractive to males before emergence from the pupa and attractiveness decreases in older females. The pheromones seem to be located on the surface of several body compartments of freshly emerged females. Sexual pheromones of all three species represent multicomponent blends and can be separated in several fractions via thin layer chromatography (TLC). Males of all species show courtship behaviour when placed on developed TLC sheets, indicating the position of the biologically active compounds. In B. difformis and B. optata, the most non‐polar TLC fraction is attractive to males, whereas the single fractions of B. tilicola‐pheromone elicited almost no attraction of males.

The Evolution of Gene Regulation Underlies a Morphological Difference between Two Drosophila Sister Species

Understanding the mechanisms underlying the morphological divergence of species is one of the central goals of evolutionary biology. Here, we analyze the genetic and molecular bases of the divergence of body pigmentation patterns between Drosophila yakuba and its sister species Drosophila santomea. We found that loss of pigmentation in D. santomea involved the selective loss of expression of the tan and yellow pigmentation genes. We demonstrate that tan gene expression was eliminated through the mutational inactivation of one specific tan cis-regulatory element (CRE) whereas the Tan protein sequence remained unchanged. Surprisingly, we identify three independent loss-of-function alleles of the tan CRE in the young D. santomea lineage. We submit that there is sufficient empirical evidence to support the general prediction that functional evolutionary changes at pleiotropic loci will most often involve mutations in their discrete, modular cis-regulatory elements.

Developmental and tissue-specific accumulation pattern for the Drosophila melanogaster TART ORF1 protein

The TART, HeT-A, and TAHRE families of Drosophila non-LTR retrotransposons specifically retrotranspose to telomeres to maintain telomeric DNA. Recent evidence indicates that an RNA interference mechanism is likely to regulate TART, HeT-A, and TAHRE retrotransposition, but the developmental and tissue-specific expression of telomeric retrotransposon proteins has not previously been investigated. We have generated antisera against TART ORF1 protein (ORF1p) and used these antisera to examine the pattern of TART ORF1p expression in Drosophila melanogaster. We detected TART ORF1p throughout most of development and observed particularly high levels of protein in late larval and pupal stages. In late-stage larvae, ORF1p accumulates in brain and imaginal discs tissues, rather than in terminally differentiated larval tissues. Accumulation of ORF1p in imaginal discs is intriguing, since TART antisense RNA has previously been detected in imaginal discs, and we discuss the implications of these findings for TART regulation.

Characterization and expression of the β-N-acetylhexosaminidase gene family of Tribolium castaneum

Enzymes belonging to the β-N-acetylhexosaminidase family cleave chitin oligosaccharides produced by the action of chitinases on chitin into the constituent N-acetylglucosamine monomer. Four genes encoding putative chitooligosaccharidolytic β-N-acetylhexosaminidases (hereafter referred to as N-acetylglucosaminidases (NAGs)) in the red flour beetle, Tribolium castaneum, namely TcNAG1, TcFDL, TcNAG2, and TcNAG3, and three other related hexosaminidases were identified by searching the recently completed genome [Tribolium Genome Sequencing Consortium, 2007. The first genome sequence of a beetle, Tribolium castaneum, a model for insect development and pest biology. Nature, submitted for publication]. Full-length cDNAs for all four NAGs were cloned and sequenced, and the exon–intron organization of the corresponding genes was determined. Analyses of their developmental expression patterns indicated that, although all four of the NAGs are transcribed during most developmental stages, each gene had a distinct spatial and temporal expression pattern. TcNAG1 transcripts are the most abundant, particularly at the late pupal stage, while TcNAG3 transcripts are the least abundant, even at their peak levels in the late larval stages. The function of each NAG during different developmental stages was assessed by observations of lethal phenotypes after gene-specific double-stranded RNA (dsRNA)-mediated transcript depletion as verified by real-time PCR. TcNAG1 dsRNA was most effective in interrupting all three types of molts: larval–larval, larval–pupal, and pupal–adult. Treated insects died after failing to completely shed their old cuticles. Knockdown of transcripts for the other three NAG genes resulted in phenotypes similar to those of TcNAG1 dsRNA-treated insects, but the effects were somewhat variable and less severe. Sequence comparisons with other enzymatically characterized insect homologs suggested that TcFDL, unlike the other NAGs, may have a role in N-glycan processing in addition to its apparent role in cuticular chitin turnover. These results support the hypothesis that TcNAGs participate in chitin turnover and/or N-glycan processing during insect development and that each NAG fulfills an essential and distinct function.

Identification and Biosynthetic Studies of the Hydrocarbon Sex Pheromone in Utetheisa ornatrix

The type II class of sex pheromones found in moths is composed of polyene hydrocarbons and their epoxides. Analysis of Utetheisa ornatrix females by gas chromatography-mass spectrometry and measurement of responses of male moths by coupled gas chromatography-electroantennogram detection confirmed the presence of large amounts of (Z,Z,Z)-1,3,6,9-heneicosatetraene (1,3,6,9-21:Hy) and smaller amounts of (Z,Z, Z)-3,6,9-heneicosatriene (3,6,9-21:Hy). Both compounds were detected in pheromone glands of newly emerged adults, with low amounts found in the late pupal stage, indicating that sex pheromone biosynthesis started in the late pupal stage. In our population of females (several hundred sampled), approximately 90% produced the tetraene, 1,3,6,9-21:Hy, as the major component, while the other 10% produced only a large amount (1500-2000 ng) of 3,6,9-21:Hy, with no detectable amount of the tetraene. This result could indicate that two distinct populations are present in our original collection site in Florida. Decapitated female moths accumulated 3,6,9-21:Hy and 1,3,6,9-21:Hy compared to the same age normal females, indicating that female moths continuously produce pheromone. A pheromone biosynthesis activating neuropeptide (PBAN)-like neuropeptide did not affect sex pheromone production as indicated by injection of synthetic PBAN and decapitation of U. ornatrix female adults. When the labeled precursor, D4-9,12,15-18:acid, was injected into the early pupal stage, the most abundantly labeled hydrocarbons were 3,6,9-21:Hy and 1,3,6,9-21:Hy in the female adults. This result indicated that 3,6,9-21:Hy could be biosynthesized from linolenic acid through chain elongation and decarboxylation. To determine how 1,3,6,9-21:Hy is produced, D4-3,6,9-21:Hy was injected into pupae and monitored for incorporation of label. No label was incorporated into 1,3,6,9-21:Hy, although a large amount of triene, 3,6,9-21 :Hy, was recovered in the pheromone gland. This indicates that U. ornatrix females do not use 3,6,9-21:Hy to produce 1,3,6,9-21:Hy, and the terminal double bond is introduced earlier in the biosynthetic pathway.

Germ-cell cluster formation in the telotrophic meroistic ovary of Tribolium castaneum (Coleoptera, Polyphaga, Tenebrionidae) and its implication on insect phylogeny

Tribolium castaneum has telotrophic meroistic ovarioles of the Polyphaga type. During larval stages, germ cells multiply in a first mitotic cycle forming many small, irregularly branched germ-cell clusters which colonize between the anterior and posterior somatic tissues in each ovariole. Because germ-cell multiplication is accompanied by cluster splitting, we assume a very low number of germ cells per ovariole at the beginning of ovariole development. In the late larval and early pupal stages, we found programmed cell death of germ-cell clusters that are located in anterior and middle regions of the ovarioles. Only those clusters survive that rest on posterior somatic tissue. The germ cells that are in direct contact with posterior somatic cells transform into morphologically distinct pro-oocytes. Intercellular bridges interconnecting pro-oocytes are located posteriorly and are filled with fusomes that regularly fuse to form polyfusomes. Intercellular bridges connecting pro-oocytes to pro-nurse cells are always positioned anteriorly and contain small fusomal plugs. During pupal stages, a second wave of metasynchronous mitoses is initiated by the pro-oocytes, leading to linear subclusters with few bifurcations. We assume that the pro-oocytes together with posterior somatic cells build the center of determination and differentiation of germ cells throughout the larval, pupal, and adult stages. The early developmental pattern of germ-cell multiplication is highly similar to the events known from the telotrophic ovary of the Sialis type. We conclude that among the common ancestors of Neuropterida and Coleoptera, a telotrophic meroistic ovary of the Sialis type evolved, which still exists in Sialidae, Raphidioptera, and a myxophagan Coleoptera family, the Hydroscaphidae. Consequently, the telotrophic ovary of the Polyphaga type evolved from the Sialis type.

Specification and development of the pars intercerebralis and pars lateralis, neuroendocrine command centers in the Drosophila brain

The central neuroendocrine system in the Drosophila brain includes two centers, the pars intercerebralis (PI) and pars lateralis (PL). The PI and PL contain neurosecretory cells (NSCs) which project their axons to the ring gland, a complex of peripheral endocrine glands flanking the aorta. We present here a developmental and genetic study of the PI and PL. The PI and PL are derived from adjacent neurectodermal placodes in the dorso-medial head. The placodes invaginate during late embryogenesis and become attached to the brain primordium. The PI placode and its derivatives express the homeobox gene Dchx1 and can be followed until the late pupal stage. NSCs labeled by the expression of Drosophila insulin-like peptide (Dilp), FMRF, and myomodulin form part of the Dchx1 expressing PI domain. NSCs of the PL can be followed throughout development by their expression of the adhesion molecule FasII. Decapentaplegic (Dpp), secreted along the dorsal midline of the early embryo, inhibits the formation of the PI and PL placodes; loss of the signal results in an unpaired, enlarged placodeal ectoderm. The other early activated signaling pathway, EGFR, is positively required for the maintenance of the PI placode. Of the dorso-medially expressed head gap genes, only tailless (tll) is required for the specification of the PI. Absence of the corpora cardiaca, the endocrine gland innervated by neurosecretory cells of the PI and PL, does not affect the formation of the PI/PL, indicating that inductive stimuli from their target tissue are not essential for early PI/PL development.

Influence of cold storage on pupal development and mortality during storage and on post-storage performance of Encarsia formosa and Eretmocerus eremicus (Hymenoptera: Aphelinidae)

Abstract Pupae of Encarsia formosa were cold stored to determine the influence of low temperature and the duration of exposure on their development and mortality during storage, and on the pattern of eclosion following storage. Eclosion, the process of extraction of a pharate adult from the host scale, was prevented at temperatures below 10 °C although the pupae continued to develop even at 4 °C. The middle stages of E. formosa pupae appeared to suffer lower mortality due to chilling compared to early or late pupal stages. Detrimental effects of cold, expressed as pupal mortality, accumulated and increased as temperature was lowered and duration of storage extended. When compared to parasitoids that had not been stored, eclosion of E. formosa was advanced following storage at 10 °C as pupae continued to develop during storage, and delayed following storage at 4 and 7 °C, possibly due to high mortality of late pupal stages. To determine the influence of different storage regimes on eclosion, flight and parasitism, pupae of E. formosa and Eretmocerus eremicus were exposed to a continuous (7 °C) and an acclimation (12 °C for 7 days, followed by 7 °C) storage regime. All three fitness parameters declined with increased duration of cold storage and its harmful effects accumulated and increased over time. The patterns of decline for eclosion and flight relative to storage duration were different between the two storage regimes; acclimated pupae tolerated cold better. Unlike for eclosion and flight, the pattern of decline for parasitism was similar between storage regimes. Enhanced tolerance to cold could be attributed to acclimation and/or pupal development to a stage more tolerant to low temperatures. To assess the cumulative impact of cold storage on the biological control potential of the two parasitoids, we constructed a composite quality index model by combining results from eclosion, flight, and parasitism. The pattern of decline in the index relative to storage duration resembled the decline observed for parasitism. The composite model predicts fewer, but more realistic gains from the use of the acclimation regime than those predicted by individual models.

Involvement of cytochrome P450 monooxygenases in the response of mosquito larvae to dietary plant xenobiotics

The response of mosquito larvae to plant toxins found in their breeding sites was investigated by using Aedes aegypti larvae and toxic arborescent leaf litter as experimental models. The relation between larval tolerance to toxic leaf litter and cytochrome P450 monooxygenases (P450 s) was examined at the toxicological, biochemical and molecular levels. Larvae pre-exposed to toxic leaf litter show a higher tolerance to those xenobiotics together with a strong increase in P450 activity levels. This enzymatic response is both time- and dose-dependent. The use of degenerate primers from various P450 genes ( CYPs) allowed us to isolate 16 new CYP genes belonging to CYP4, CYP6 and CYP9 families. Expression studies revealed a 2.3-fold over-expression of 1 CYP gene ( CYP6AL1) after larval pre-exposure to toxic leaf litter, this gene being expressed at a high level in late larval and pupal stages and in fat bodies and midgut. The CYP6AL1 protein has a high level of identity with other insect's CYPs involved in xenobiotic detoxification. The role of CYP genes in tolerance to natural xenobiotics and the importance of such adaptive responses in the capacity of mosquitoes to colonize new habitats and to develop insecticide resistance mechanisms are discussed.

Synaptogenesis in the mushroom body calyx during metamorphosis in the honeybeeApis mellifera: An electron microscopic study

The goals of this study are to determine relationships between synaptogenesis and morphogenesis within the mushroom body calyx of the honeybee Apis mellifera and to find out how the microglomerular structure characteristic for the mature calyx is established during metamorphosis. We show that synaptogenesis in the mushroom body calycal neuropile starts in early metamorphosis (stages P1-P3), before the microglomerular structure of the neuropile is established. The initial step of synaptogenesis is characterized by the rare occurrence of distinct synaptic contacts. A massive synaptogenesis starts at stage P5, which coincides with the formation of microglomeruli, structural units of the calyx that are composed of centrally located presynaptic boutons surrounded by spiny postsynaptic endings. Microglomeruli are assembled either via accumulation of fine postsynaptic processes around preexisting presynaptic boutons or via ingrowth of thin neurites of presynaptic neurons into premicroglomeruli, tightly packed groups of spiny endings. During late pupal stages (P8-P9), addition of new synapses and microglomeruli is likely to continue. Most of the synaptic appositions formed there are made by boutons (putative extrinsic mushroom body neurons) into small postsynaptic profiles that do not exhibit presynaptic specializations (putative intrinsic mushroom body neurons). Synapses between presynaptic boutons characteristic of the adult calyx first appear at stage P8 but remain rare toward the end of metamorphosis. Our observations are consistent with the hypothesis that most of the synapses established during metamorphosis provide the structural basis for afferent information flow to calyces, whereas maturation of local synaptic circuitry is likely to occur after adult emergence.

The Roles of Two Clip Domain Serine Proteases in Innate Immune Responses of the Malaria Vector Anopheles gambiae

The malaria vector Anopheles gambiae is capable of multiple immune responses against Plasmodium ookinetes. Accumulating evidence in several insect species suggests the involvement of serine protease cascades in the initiation and coordination of immune responses. We report molecular and reverse genetic characterization of two mosquito clip domain serine proteases, CLIPB14 and CLIPB15, which share structural similarity to proteases involved in prophenoloxidase activation in other insects. Both CLIPs are expressed in mosquito hemocytes and are transcriptionally induced by bacterial and Plasmodium challenges. Functional studies applying RNA interference revealed that both CLIPs are involved in the killing of Plasmodium ookinetes in Anopheles. Studies on parasite melanization demonstrated an additional role for CLIPB14 in the prophenoloxidase cascade. We further report that both CLIPs participate in defense toward Gram-negative bacteria. Our findings strongly suggest that clip domain serine proteases serve multiple functions and play distinctive roles in several immune pathways of A. gambiae.

Calcineurin function is required for myofilament formation and troponin I isoform transition in Drosophila indirect flight muscle

Mutations in the Drosophila calcineurin B2 gene cause the collapse of indirect flight muscles during mid stages of pupal development. Examination of cell fate-specific markers indicates that unlike mutations in genes such as vestigial, calcineurin B2 does not cause a shift in cell fate from indirect flight muscle to direct flight muscle. Genetic and molecular analyses indicate a severe reduction of myosin heavy chain gene expression in calcineurin B2 mutants, which accounts at least in part for the muscle collapse. Myofibrils in calcineurin B2 mutants display a variety of phenotypes, ranging from normal to a lack of sarcomeric structure. Calcineurin B2 also plays a role in the transition to an adult-specific isoform of troponin I during the late pupal stages, although the incompleteness of this transition in calcineurin B2 mutants does not contribute to the phenotype of muscle collapse. Together, these findings suggest a molecular basis for the indirect flight muscle hypercontractility phenotype observed in flies mutant for Drosophila calcineurin B2.

Properties of Orange-Pupa-Inducing Factor (OPIF) in the swallowtail butterfly, Papilio xuthus L.

Diapause pupae of the swallowtail butterfly Papilio xuthus L. exhibit diapause-green, orange and brownish-orange color polymorphism. Development of orange pupae involves a neuroendocrine factor inducing orange pupa (Orange-Pupa-Inducing Factor, OPIF), which is secreted from the head–thoracic region during late pharate pupal stages, in particular from the ganglia of short-day animals located posteriorly from the second thoracic ganglion 2 (TG 2). This report describes certain properties of OPIF using bioassays involving ligated abdomens of short-day pharate pupae. Localization of OPIF in the central nervous system of short-day larvae indicated that it was present predominantly in TG 2, thoracic ganglion 3 (TG 3) and abdominal ganglion 1 (AG 1) complexes. OPIF activity in TG 2,3–AG 1 complexes was over two times higher than in the more posteriorely located ganglia. The developmental profile of OPIF in last instar short-day larvae revealed that OPIF activity in larval ganglia posterior to TG 2 became gradually higher as larval growth proceeded, suggesting that OPIF might be accumulated in TG 2,3–AG 1–7 complexes as larvae prepare for pupal molting. Furthermore, ligated abdomens of short-day larvae developed into pupae of an orange type when a 2% NaCl extract containing OPIF prepared from TG 2,3–AG 1–7 complexes of long-day larvae was injected into ligated abdomens of short-day pharate pupae, indicating that OPIF is also present in long-day larvae. Additionally, a biochemical investigation using gel filtration chromatography showed that the molecular weight of OPIF was about 10 kDa.

DPATJ plays a role in retinal morphogenesis and protects against light‐dependent degeneration of photoreceptor cells in the Drosophila eye

The establishment of apicobasal polarity in epithelial cells is a prerequisite for their function. Drosophila photoreceptor cells derive from epithelial cells, and their apical membranes undergo elaborate differentiation during pupal development, forming photosensitive rhabdomeres and associated stalk membranes. Crumbs (Crb), a transmembrane protein involved in the maintenance of epithelial polarity in the embryo, defines the stalk as a subdomain of the apical membrane. Crb organizes a complex composed of several PDZ domain-containing proteins, including DPATJ (formerly known as Discs lost). Taking advantage of a DPATJ mutant line in which only a truncated form of the protein is synthesized, we demonstrate that DPATJ is necessary for the stability of the Crb complex at the stalk membrane and is crucial for stalk membrane development and rhabdomere maintenance during late pupal stages. Moreover, DPATJ protects against light-induced photoreceptor degeneration.

Null mutants of Drosophila B-type lamin Dm0 show aberrant tissue differentiation rather than obvious nuclear shape distortion or specific defects during cell proliferation

To elucidate the function of metazoan B-type lamins during development, new null mutations of the Drosophila B-type lamin gene, lamDm 0 , were analyzed in parallel with the misg sz18 mutation, a lamDm 0 allele reported previously. Although in all these mutants, lamin Dm 0 protein was undetectable in neuroblasts and imaginal disc cells from the second instar larval stage onward, cells continued to proliferate. In contrast to the embryonic lethality of another Drosophila lamDm 0 allele, lam PM15 , reported previously, lethality did not occur until late pupal stages. Chromosomal structure and the overall nuclear shape remained normal even at these late pupal stages, although obviously abnormal nuclear pore complex distribution was observed concomitant with the loss of lamin Dm 0 protein. Compensating expression of lamin C was not induced in the absence of lamin Dm 0. Thus, no lamin-containing nuclear structures were found in proliferating larval neuroblasts. We did find that developmental abnormalities appeared in specific organs during the late pupal stage, preceding lethality. Surprisingly, coordinated size increase (hypertrophy) of the ventriculus was observed accompanied by cell division and muscle layer formation. Hypertrophy of the ventriculus correlated with a decrease in ecdysteroid hormone receptor B1 (EcRB1) protein, and furthermore could be suppressed by a heat-inducible EcRB1 transgene. In contrast, both gonadal and CNS tissues exhibited underdevelopment.