Drumstick is a zinc finger protein that antagonizes Lines to control patterning and morphogenesis of the Drosophila hindgut

Elongation of the Drosophila embryonic hindgut epithelium occurs by a process of oriented cell rearrangement requiring the genes drumstick (drm) and lines (lin). The elongating hindgut becomes subdivided into domains -- small intestine, large intestine and rectum -- each characterized by a specific pattern of gene expression dependent upon normal drm and lin function. We show that drm encodes an 81 amino acid (10 kDa) zinc finger protein that is a member of the Odd-skipped family. drm expression is localized to the developing midgut-hindgut junction and is required to establish the small intestine, while lin is broadly expressed throughout the gut primordium and represses small intestine fate. lin is epistatic to drm, suggesting a model in which localized expression of drm blocks lin activity, thereby allowing small intestine fate to be established. Further supporting this model, ectopic expression of Drm throughout the hindgut produces a lin phenotype. Biochemical and genetic data indicate that the first conserved zinc finger of Drm is essential for its function. We have thus defined a pathway in which a spatially localized zinc finger protein antagonizes a globally expressed protein, thereby leading to specification of a domain (the small intestine) necessary for oriented cell rearrangement.     

Genes controlling posterior gut development in theDrosophila embryo

Our present detailed understanding of the genetic mechanisms controlling segmentation has been made possible, in large part, by comprehensive screens of cuticular morphology that identified genes involved in epidermal patterning. To systematically identify genes involved in internal morphogenesis, specifically development of the gut, we have screened mutant embryos produced by a collection of 53 embryonic lethal mutations affecting embryonic pattern formation or differentiation, and a collection of 161 deficiencies covering, in aggregate, approximately 70% of the genome. Staining with the anti-crumbs antibody was used to characterize the Malpighian tubules and hindgut, as well as other internal organs. The geneshuckebein, tailless andwingless, and two previously undescribed loci at 24C/D and 68D/E, are required to establish the primordia for the posterior midgut and hindgut/Malpighian tubules. A locus in region 30A/C is required for extension of the midgut epithelium to surround the yolk, and region 36E/37F is required for outbudding of the Malpighian tubule primordia. Several deficiencies were identified that uncover loci with specific effects on the morphogenesis (elongation, lumen formation) of the hindgut and Malpighian tubules and on the formation of constrictions in the midgut.     

Role of Scrib and Dlg in anterior-posterior patterning of the follicular epithelium during Drosophila oogenesis

Background  

Proper patterning of the follicle cell epithelium over the egg chamber is essential for the Drosophila egg development. Differentiation of the epithelium into several distinct cell types along the anterior-posterior axis requires coordinated activities of multiple signaling pathways. Previously, we reported that lethal(2)giant larvae (lgl), a Drosophila tumor suppressor gene, is required in the follicle cells for the posterior follicle cell (PFC) fate induction at mid-oogenesis. Here we explore the role of another two tumor suppressor genes, scribble (scrib) and discs large (dlg), in the epithelial patterning.     

Immunological differences in intestine and rectum of Atlantic cod (Gadus morhua L.)

The defence system of the distal gut (hindgut and rectum) of Atlantic cod, (Gadus morhua L.) was studied using (immuno)histochemical, electron microscopical and real-time quantitative PCR techniques. The uptake and transport of macromolecules in the intestinal epithelium was also investigated.In this study we observed that cod has many and large goblet cells in its intestinal epithelium and that IgM⁺ cells are present in the lamina propria and their number is considerably higher in the rectum than in the intestine. Myeloperoxidase staining revealed low numbers of granulocytes in and under the epithelium of the distal intestine, whereas high numbers were found clustered in the submucosa of the rectum. Electron microscopy not only confirmed these observations, but also revealed the presence of lymphoid cells and macrophages within the intestinal epithelium. Acid phosphatase staining demonstrated more positive macrophage-like cells in the rectum than in the distal intestine. Antigen uptake studies showed a diffused absorption of horse radish peroxidase (HRP) and LTB-GFP, whereas ferritin uptake could not be detected.Basal gene expression of cytokines (IL-1β, IL-8 and IL-10) and immune relevant molecules (hepcidin and BPI/LPB) were compared in both the intestine and rectum and revealed approximately 2–9 times higher expression in the rectum, of which IL-1β expression showed the most prominent difference.The present results clearly indicate that intestinal immunity is very prominent in the rectum of cod.     

patufet , the gene encoding the Drosophila melanogaster homologue of selenophosphate synthetase, is involved in imaginal disc morphogenesis

Proliferation in imaginal discs requires cell growth and is linked to patterning processes controlled by secreted cell-signalling molecules. To identify new genes involved in the control of cell proliferation we have screened a collection of P-lacW insertion mutants that result in lethality in the larval/pupal stages, and characterized a novel gene, patufet (ptuf). Inactivation of ptuf by a P element insertion in the 5′ untranslated region leads to aberrant imaginal disc morphology characterized by a reduction in mass of discs and disorganisation of disc cells where no folding or patterning can be detected. Moreover, apoptotic cells can be observed in these small and abnormal mutant discs. To examine the role of ptuf we have studied its clonal behaviour in genetic mosaics generated by mitotic recombination. The mutation causes reduced cell viability, smaller cell size and stops vein differentiation. Non-autonomous effects, such as abnormal differentiation of wild-type cells surrounding the clones, are also observed. We have cloned the ptuf gene of Drosophila melanogaster and found that it encodes a selenophosphate synthetase, which is the first identified in insects. Mutant flies transformed with the full-length cDNA show complete reversion of lethality and disc phenotype. Northern blot analysis and in situ hybridization indicate that the ptuf gene is expressed in imaginal discs as well as at different stages of development. The synthesis of selenoproteins by the selenophosphate synthetase, the role of selenoproteins in the maintenance of the oxidant/antioxidant balance of the cell and its possible implications in imaginal disc morphogenesis are discussed. Received: 22 August 1997 / Accepted: 9 September 1997     

Selective loss of <Emphasis Type="Italic">lin</Emphasis> genes from hexachlorocyclohexane-degrading <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> ITRC-5 under different growth conditions

The chlorinated insecticide γ-hexachlorocyclohexane (γ-HCH) is sequentially metabolized by the products of linA, linB, linC, linD, linE, and linF genes to β-ketoadipate, which is subsequently mineralized. Two or more copies of these genes are present in the bacterium Pseudomonas aeruginosa ITRC-5 that was isolated earlier by selective enrichment on technical-HCH. At least one copy of linA, linB, linC, linD, and possibly linE is lost from ITRC-5 upon its growth on γ-HCH. All the lin genes, however, are lost when the bacterium was grown in Luria–Bertani (LB) medium. The loss of lin genes is accompanied with the loss/rearrangement of insertion sequence IS6100 genes. Concomitant to the loss of lin genes, the degradation of HCH-isomers by “γ-HCH grown cells” is slower, when compared with “technical-HCH grown cells”, and is completely lost by “LB-grown cells”. The selective loss of lin genes during different growth conditions has not been reported before and is expected to help in understanding the dynamism of degradative genes.     

Effects of MULTIFOLIATE-PINNA, AFILA, TENDRIL-LESS and UNIFOLIATA genes on leafblade architecture in Pisum sativum

In order to dissect the genetic regulation of leafblade morphogenesis, 16 genotypes of pea, constructed by combining the wild-type and mutant alleles of MFP, AF, TL and UNI genes, were quantitatively phenotyped. The morphological features of the three domains of leafblades of four genotypes, unknown earlier, were described. All the genotypes were found to differ in leafblade morphology. It was evident that MFP and TL functions acted as repressor of pinna ramification, in the distal domain. These functions, with and without interaction with UNI, also repressed the ramification of proximal pinnae in the absence of AF function. The expression of MFP and TL required UNI function. AF function was found to control leafblade architecture multifariously. The earlier identified role of AF as a repressor of UNI in the proximal domain was confirmed. Negative control of AF on the UNI-dependent pinna ramification in the distal domain was revealed. It was found that AF establishes a boundary between proximal and distal domains and activates formation of leaflet pinnae in the proximal domain.     

Tissue-specific and constitutive expression of a hypothetical gene At2g37610 in transgenic Arabidopsis

Hypothetical genes should play important roles in plant growth and development, although their biological functions await elucidation. One of these genes, namely At2g37610, caught our attention during the gene cloning of several salt-tolerant mutants. Promoter-GUS fusion analysis indicated a unique tissue-specific expression pattern of At2g37610 in Arabidopsis. Constitutive expression of the gene under 35S promoter caused obvious morphological changes in transgenic Arabidopsis plants, such as curled rosette leaves and bushy phenotype at maturity. Phenotypic characterization revealed that the cause of the bushy phenotype was the enhanced lateral bud outgrowth at the bottom region of the primary inflorescence, which is different from that of reported mutant plants (bushy or branched) such as max, axr1, and bus mutants. Together, these data suggest that At2g37610 is a possible novel gene related to the regulation of leaf development and shoot patterning.     

Bmp7 expression and null phenotype in the urogenital system suggest a role in re-organization of the urethral epithelium

Signaling by Bone morphogenetic proteins (Bmps) has multiple and diverse roles in patterning and morphogenesis of the kidney, eye, limbs and the neural tube. Here, we employed the Bmp7^lacZ strain to perform a detailed analysis of Bmp7 expression and the null phenotype during development of the mouse urogenital system. The urethral compartment originates in mid-embryogenesis from the ventral part of the cloaca, a transient cavity at the caudal end of the hindgut. At mid-gestation, Bmp7 expression was detected within several specific domains in the cloacal epithelium and mesenchyme. In late embryogenesis, Bmp7 expression was present in the urethra, rectum, the urethral glands, corpus cavernosum, and in the male and female genital ducts. Importantly, loss of Bmp7 resulted in arrest in cloacal septation, and severe defects in morphogenesis of the genital urethra and mesenchyme. Together, our analysis of Bmp7 expression and the null phenotype, indicates that Bmp7 may play an important role in re-organization of the epithelium during cloacal septation and morphogenesis of the genital tubercle.     

Sfrp Controls Apicobasal Polarity and Oriented Cell Division in Developing Gut Epithelium

Epithelial tubular morphogenesis leading to alteration of organ shape has important physiological consequences. However, little is known regarding the mechanisms that govern epithelial tube morphogenesis. Here, we show that inactivation of Sfrp1 and Sfrp2 leads to reduction in fore-stomach length in mouse embryos, which is enhanced in the presence of the Sfrp5 mutation. In the mono-cell layer of fore-stomach epithelium, cell division is normally oriented along the cephalocaudal axis; in contrast, orientation diverges in the Sfrps-deficient fore-stomach. Cell growth and apoptosis are not affected in the Sfrps-deficient fore-stomach epithelium. Similarly, cell division orientation in fore-stomach epithelium diverges as a result of inactivation of either Stbm/Vangl2, an Fz/PCP component, or Wnt5a. These observations indicate that the oriented cell division, which is controlled by the Fz/PCP pathway, is one of essential components in fore-stomach morphogenesis. Additionally, the small intestine epithelium of Sfrps compound mutants fails to maintain proper apicobasal polarity; the defect was also observed in Wnt5a-inactivated small intestine. In relation to these findings, Sfrp1 physically interacts with Wnt5a and inhibits Wnt5a signaling. We propose that Sfrp regulation of Wnt5a signaling controls oriented cell division and apicobasal polarity in the epithelium of developing gut.     

A gene cluster for amylovoran synthesis in Erwinia amylovora: characterization and relationship to cps genes in Erwinia stewartii

A large ams gene cluster required for production of the acidic extracellular polysaccharide (EPS) amylovoran by the fire blight pathogen Erwinia amylovora was cloned. Tn5 mutagenesis and gene replacement were used to construct chromosomal ams mutants. Five complementation groups, essential for amylovoran synthesis and virulence in E. amylovora, were identified and designated amsA-E. The ams gene cluster is about 7 kb in size and functionally equivalent to the cps gene cluster involved in EPS synthesis by the related pathogen Erwinia stewartii. Mucoidy and virulence were restored to E. stewartii mutants in four cps complementation groups by the cloned E. amylovora ams genes. Conversely, the E. stewartii cps gene cluster was able to complement mutations in E. amylovora ams genes. Correspondence was found between the amsA-E complementation groups and the cpsB-D region, but the arrangement of the genes appears to be different. EPS production and virulence were also restored to E. amylovora amsE and E. stewartii cpsD mutants by clones containing the Rhizobium meliloti exoA gene.     

Genomic organization and genomic structural rearrangements of Sphingobium japonicum UT26, an archetypal γ-hexachlorocyclohexane-degrading bacterium

The complete genome sequencing of a γ-hexachlorocyclohexane-degrading strain, Sphingobium japonicum UT26, revealed that the genome consists of two circular chromosomes [with sizes of 3.5 Mb (Chr1) and 682 kb (Chr2)], a 191-kb large plasmid (pCHQ1), and two small plasmids with sizes of 32 and 5 kb. The lin genes are dispersed on Chr1, Chr2, and pCHQ1. Comparison of the UT26 genome with those of other sphingomonad strains demonstrated that the “specific” lin genes for conversion of γ-HCH to β-ketoadipate (linA, linB, linC, linRED, and linF) are located on the DNA regions unique to the UT26 genome, suggesting the acquisition of these lin genes by horizontal transfer events. On the other hand, linGHIJ and linKLMN are located on the regions conserved in the genomes of sphingomonads, suggesting that the linGHIJ-encoded β-ketoadipate pathway and the LinKLMN-type ABC transporter system are involved in core functions of sphingomonads. Based on these results, we propose a hypothesis that UT26 was created by recruiting the specific lin genes into a strain having core functions of sphingomonads. Most of the specific lin genes in UT26 are associated with IS6100. Our analysis of spontaneous linA-, linC-, and linRED-deletion mutants of UT26 revealed the involvement of IS6100 in their deduced genome rearrangements. These facts strongly suggest that IS6100 plays important roles both in the dissemination of the specific lin genes and in the genome rearrangements.     

Genetic analysis of essential genes in the ftsE region of the Escherichia coli genetic map and identification of a new cell division gene, ftsS

Summary Several conditional lethal mutants of Escherichia coli have been analysed genetically using generalized transduction and lambda transducing vectors. Three temperature-sensitive ftsE mutants were found as was a cold-sensitive ftsE mutant. A new gene was foud which mapped close to ftsE, namely ftsS. Both cell division genes map close to the gene which controls the heat-shock regulon (htpR).     

Disrupted dorsal neural tube BMP signaling in the cilia mutant Arl13b stems from abnormal Shh signaling

In the embryonic neural tube, multiple signaling pathways work in concert to create functional neuronal circuits in the adult spinal cord. In the ventral neural tube, Sonic hedgehog (Shh) acts as a graded morphogen to specify neurons necessary for movement. In the dorsal neural tube, bone morphogenetic protein (BMP) and Wnt signals cooperate to specify neurons involved in sensation. Several signaling pathways, including Shh, rely on primary cilia in vertebrates. In this study, we used a mouse mutant with abnormal cilia, Arl13b^hnn, to study the relationship between cilia, cell signaling, and neural tube patterning. Arl13b^hnn mutants have abnormal ventral neural tube patterning due to disrupted Shh signaling; in addition, dorsal patterning defects occur, but the cause of these is unknown. Here we show that the Arl13b^hnn dorsal patterning defects result from abnormal BMP signaling. In addition, we find that Wnt ligands are abnormally expressed in Arl13b^hnn mutants; surprisingly, however, downstream Wnt signaling is normal. We demonstrate that Arl13b is required non-autonomously for BMP signaling and Wnt ligand expression, indicating that the abnormal Shh signaling environment in Arl13b^hnn embryos indirectly causes dorsal defects.     

The interaction of epithelial Ihha and mesenchymal Fgf10 in zebrafish esophageal and swimbladder development

Developmental patterning and growth of the vertebrate digestive and respiratory tracts requires interactions between the epithelial endoderm and adjacent mesoderm. The esophagus is a specialized structure that connects the digestive and respiratory systems and its normal development is critical for both. Shh signaling from the epithelium regulates related aspects of mammalian and zebrafish digestive organ development and has a prominent effect on esophageal morphogenesis. The mechanisms underlying esophageal malformations, however, are poorly understood. Here, we show that zebrafish Ihha signaling from the epithelium acting in parallel, but independently of Shh, controls epithelial and mesenchymal cell proliferation and differentiation of smooth muscles and neurons in the gut and swimbladder. In zebrafish ihha mutants, the esophageal and swimbladder epithelium is dysmorphic, and expression of fgf10 in adjacent mesenchymal cells is affected. Analysis of the development of the esophagus and swimbladder in fgf10 mutant daedalus (dae) and compound dae/ihha mutants shows that the Ihha–Fgf10 regulatory interaction is realized through a signaling feedback loop between the Ihha-expressing epithelium and Fgf10-expressing mesenchyme. Disruption of this loop further affects the esophageal and swimbladder epithelium in ihha mutants, and Ihha acts in parallel to but independently of Shha in this process. These findings contribute to the understanding of epithelial–mesenchymal interactions and highlight an interaction between Hh and Fgf signaling pathways during esophagus and swimbladder development.