Regulatory interactions and role in cell type specification of the Malpighian tubules by the cut, Krüppel, and caudal genes of Drosophila.

Krüppel and caudal genes are both required for normal segmentation of the embryo, and the developmental regulatory gene cut is necessary for the normal specification of external sensory organs. These three genes are also expressed in the Malpighian tubules before and during differentiation. Two of the genes, Krüppel and cut, are known to be required for development of the tubules. We report that the absence of maternal and zygotic caudal function reduces their normal growth and elongation. Normal Krüppel function, which is known to be required for caudal expression, is also required for cut expression, while cut and caudal are expressed independently of each other. Cell type transformations of Malpighian tubules were studied by examining the effects of mutations on the expression of markers specific to Malpighian tubules, hindgut, or midgut of normal embryos. Loss of Krüppel activity confers hindgut characteristics on those cells that normally form the Malpighian tubules with all markers tested. Loss of cut function alters the expression of some markers but not others. The pathway of tissue specific gene regulation, apparently, branches beyond Krüppel to form at least a cut and a caudal branch.     

Morphology and ultrastructure of the alimentary canal of the cicada Platypleura kaempferi (Hemiptera: Cicadidae)

The alimentary canal of cicada Platypleura kaempferi is described. It comprises the oesophagus, filter chamber, external midgut section and hindgut. The elongate oesophagus expands posteriorly, with its posterior end constricting to become a bulb. The filter chamber consists of two parts: a very thin sheath and a filter organ. The filter organ is composed of the anterior and posterior ends of the midgut (internal midgut section), and the internal proximal ends of the Malpighian tubules. The external midgut section differentiates into a collapsed sac and a midgut loop. The latter is divided into three distinct segments. The hindgut contains a dilated rectum and a long narrow ileum. The distal portions of the four Malpighian tubules are enclosed in a peritoneal sheath together with the distal ileum before reaching to the rectum. Ultrastructurally, the oesophagus and the hindgut are lined with a cuticle. The filter chamber sheath consists of cells with large irregular nuclei. Filamentous substances coat the microvilli of the cells of the internal midgut section. The posterior end of the midgut comprises two types of cells, with the first type of cells containing many vesicles and scattered elements of rough endoplasmic reticulum. The anterior and posterior segments of the midgut loop cells have ferritin‐like granules. The ileum cells have well‐developed apical leaflets associated with mitochondria. Accumulations of virus‐like particles enclosed in the membrane are observed in the esophagus, conical segment, mid‐ and posterior segments of the midgut loop.     

Complexity in evolved regulatory variation for alcohol dehydrogenase genes in HawaiianDrosophila

Summary The alcohol dehydrogenase gene (Adh gene) ofDrosophila affinidisjuncta is expressed at a higher level in the larval midgut and Malpighian tubules than the homologous gene fromDrosophila hawaiiensis. This study analyzed thecis-acting sequences responsible for these regulatory differences in larval tissues ofDrosophila melanogaster transformants. A series of 10 chimeric and deletedAdh genes was introduced into the germ line ofD. melanogaster, and tissue-specific expression levels were quantified by gel electrophoresis of tissue extracts. Sequences in the upstream region of the two genes had the strongest influence on enzyme production in the midgut and Malpighian tubules. Other sequence elements also showed effects, some of which were tissue specific. Most gene fragments displayed context-dependent effects, thus supporting the proposed model of polygenic regulation ofAdh gene expression.     

Phenotypic and developmental analysis of mutations at thecrumbs locus,a gene required for the development of epithelia inDrosophila melanogaster

Summary The genecrumbs (crb) ofDrosophila melanogaster provides an essential function for the embryonic development of ectodermally derived epithelia. Complete loss of function alleles of thecrb gene are recessive embryonic lethals and lead to a disorganization of the primordia of these epithelia, followed by cell death in some tissues. Incrb mutant embryos, different organs are affected to a different extent. Some tissues die almost completely (as the epidermis, the atrium and the pharynx) while others partially survive and conserve their basic epithelial structure (as the tracheal system, the oesophagus, the proventriculus, the salivary glands, the hindgut and the Malpighian tubules). Degeneration is first visible at stage 11 and continues successively throughout development. There is evidence that the loss of epithelial cell polarity may be the cause for the degeneration of these tissues, suggesting that thecrb gene product is involved in stabilizing the apico-basal polarity of epithelial cells. As previously shown, thecrb protein is specifically expressed on the apical side of embryonic epithelia in a reticular pattern outlining the borders of the cells. Here we demonstrate that thecrb protein shows the same subcellular localization in epithelial cells of imaginal discs and in follicle cells, indicating a similar function ofcrb during the development of embryonic, imaginal and follicle epithelia. Clonal analysis experiments indicate that the genecrb is not cell-autonomous in its expression, suggesting that the gene product may act as a diffusible factor and may serve as a signal in a cell-cell communication process. This signal is thought to be required for the formation and/or maintenance of the cell and tissue structure of the respective epithelia.     

Development of the Malpighian tubules in Cloeon dipterum (Ephemeroptera)

The development of the Malpighian tubules is studied in Cloeon dipterum through all stages from the youngest larva to the adult. The Malpighian tubules are found to be outgrowths of the posterior part of the endodermal midgut and not of the ectodermal hindgut. In the adult the part of the intestine with the tubule openings becomes separated by an ingrowing fold of the epithelium from the anterior main part of the midgut that forms a large thin-walled and air-filled bladder. The characteristics of the developmental stages, which served to determine the age of the animals, are given.     

The Genes Raw and Ribbon Are Required for Proper Shape of Tubular Epithelial Tissues in Drosophila

The products of two genes, raw and ribbon (rib), are required for the proper morphogenesis of a variety of tissues. Malpighian tubules mutant for raw or rib are wider and shorter than normal tubules, which are only two cells in circumference when they are fully formed. The mutations alter the shape of the tubules beginning early in their formation and block cell rearrangement late in development, which normally lengthens and narrows the tubes. Mutations of both genes affect a number of other tissues as well. Both genes are required for dorsal closure and retraction of the CNS during embryonic development. In addition, rib mutations block head involution, and broaden and shorten other tubular epithelia (salivary glands, tracheae, and hindgut) in much same manner as they alter the shape of the Malpighian tubules. In tissues in which the shape of cells can be observed readily, rib mutations alter cell shape, which probably causes the change in shape of the organs that are affected. In double mutants raw enhances the phenotypes of all the tissues that are affected by rib but unaffected by raw alone, indicating that raw is also active in these tissues.     

Expression patterns of genes encoding proteins with peritrophin A domains and protein localization in Mamestra configurata

Genes encoding three proteins (McPPAD1-3) with peritrophin A chitin-binding domains (PADs) were identified from a Mamestra configurata larval midgut cDNA library. In addition to midgut, McPPAD1-3 and a previously identified gene encoding the peritrophin, McPM1, were expressed in foregut, hindgut, Malpighian tubules, tracheae, fat body and cuticle; however, the corresponding McPPAD proteins exhibited different localization patterns. McPPAD1 was restricted to the digestive tract and Malpighian tubules, McPPAD2 to Malpighian tubules, and McPPAD3 to the foregut, midgut, hindgut, tracheae and cuticle. Protein fold recognition analysis using tachycitin as a guide structure modelled the McPPAD1 PADs, but not McPPAD2 or McPPAD3 PADs. The McPPAD1 PADs were predicted to contain three anti-parallel β-sheets and a hevein-like fold that form a chitin-binding pocket containing two hydrophobic R-groups in a sandwich-like orientation.     

Genetic Control of Development of Malpighian Tubules in Drosophila melanogaster

Malpighian tubules of insects are a functional analog of mammalian kidneys and serve as a classical model for studying the structure and functions of transport epithelium. The review contains the data on structural organization, functioning, and formation of the Malpighian tubules during embryogenesis in Drosophila melanogaster. Various systems of genes are described that control the program of development of the renal (Malpighian) tubules in D. melanogaster. A special attention is paid to the ways of signal transduction and factors involved in cell differentiation, proliferation, and morphological transformation during development of the Malpighian tubules. Evolutionarily conservative genetic systems are considered that are involved in the control of development of both the renal epithelium ofDrosophila and mammalian kidneys. A relationship was noted between the disturbed balance of genetic material and congenital defects of the human excretory system.     

Age- and diapause-related acid and alkaline phosphatase activities in the intestine and malpighian tubules of the Colorado potato beetle, Leptinotarsa decemlineata (Say)

Specific activities for soluble (s) and membrane (m)-bound acid (ACP) and alkaline phosphatases (ALP) were determined in the midgut, hindgut, and Malpighian tubules for developing, prediapausing, and diapausing adult Colorado potato beetles, Leptinotarsa decemlineata (Say). High ACP activities were found in the hindgut and Malpighian tubules while high ALP activities were found in the Malpighian tubules. Variation in both ACP and ALP activities in each tissue reflects fluctuation in protein synthesis and secretion involved with digestion, excretion, and other unknown functions. Phosphatase activities in the tissues examined show the dynamic nature of diapause in this insect. Diapausing beetles showed increases in phosphatase activity after hormone treatments. JHA treatments increased s-ACP and m-ACP activities in all tissues but 20-HE did not increase activity in any tissue. Allatotropin tended to mimic the effects of JHA treatment. The s-ALP activity was also increased in all tissues whereas m-ALP was increased in the midgut and hindgut by JHA treatment. Malpighian tubule m-ALP activity was only increased by 20-HE treatments. Allatotropin was not as effective in increasing ALP activities as it was with ACP activities.     

Regulation of Krüppel expression in the anlage of the Malpighian tubules in the Drosophila embryo

The expression of most Drosophila segmentation genes is not limited to the early blastoderm stage, when the segmental anlagen are determined. Rather, these genes are often expressed in a variety of organs and tissues at later stages of development. In contrast to the early expression, little is known about the regulatory interactions that govern the later expression patterns. Among other tissues, the central gap gene Krüppel is expressed and required in the anlage of the Malpighian tubules at the posterior terminus of the embryo. We have studied the interaction of Krüppel with other terminal genes. The gap genes tailles and huckebein, which repress Krüppel in the central segmentation domain, activate Krüppel expression in the posterior Malpighian tubule domain. The opposite effect on the posterior Krüppel expression is achieved by the interposition of another factor, the homeotic gene fork head, which is not involved in the control of the central domain. In addition, Krüppel activates different genes in the Malpighian tubules than in the central domain. Thus, both the regulation and the function of Krüppel in the Malpighian tubules differ strikingly from its role in segmentation.     

Anatomy and fine structure of the alimentary canal of the spittlebug Lepyronia coleopterata (L.) (Hemiptera: Cercopoidea)

The alimentary canal of the spittlebug Lepyronia coleopterata (L.) differentiates into esophagus, filter chamber, midgut (conical segment, tubular midgut), and hindgut (ileum, rectum). The filter chamber is composed of the anterior extremity of the midgut, posterior extremity of the midgut, proximal Malpighian tubules, and proximal ileum; it is externally enveloped by a thin cellular sheath and thick muscle layers. The sac-like anterior extremity of the midgut is coiled around by the posterior extremity of the midgut and proximal Malpighian tubules. The tubular midgut is subdivided into an anterior tubular midgut, mid-midgut, posterior tubular midgut, and distal tubular midgut. Four Malpighian tubules run alongside the ileum, and each terminates in a rod closely attached to the rectum. Ultrastructurally, the esophagus is lined with a cuticle and enveloped by circular muscles; its cytoplasm contains virus-like fine granules of high electron-density. The anterior extremity of the midgut consists of two cellular types: (1) thin epithelia with well-developed and regularly arranged microvilli, and (2) large cuboidal cells with short and sparse microvilli. Cells of the posterior extremity of the midgut have regularly arranged microvilli and shallow basal infoldings devoid of mitochondria. Cells of the proximal Malpighian tubule possess concentric granules of different electron-density. The internal proximal ileum lined with a cuticle facing the lumen and contains secretory vesicles in its cytoplasm. Dense and long microvilli at the apical border of the conical segment cells are coated with abundant electron-dense fine granules. Cells of the anterior tubular midgut contain spherical secretory granules, oval secretory vesicles of different size, and autophagic vacuoles. Ferritin-like granules exist in the mid-midgut cells. The posterior tubular midgut consists of two cellular types: 1) cells with shallow and bulb-shaped basal infoldings containing numerous mitochondria, homocentric secretory granules, and fine electron-dense granules, and 2) cells with well-developed basal infoldings and regularly-arranged apical microvilli containing vesicles filled with fine granular materials. Cells of the distal tubular midgut are similar to those of the conical segment, but lack electron-dense fine granules coating the microvilli apex. Filamentous materials coat the microvilli of the conical segment, anterior and posterior extremities of the midgut, which are possibly the perimicrovillar membrane closely related to the nutrient absorption. The lumen of the hindgut is lined with a cuticle, beneath which are cells with poorly-developed infoldings possessing numerous mitochondria. Single-membraned or double-membraned microorganisms exist in the anterior and posterior extremities of the midgut, proximal Malpighian tubule and ileum; these are probably symbiotic.     

黄脸油葫芦与短额负蝗马氏管组织结构比较

采用组织学方法对直翅目剑尾亚目和锥尾亚目的两个物种--黄脸油葫芦Teleogryllus emma和短额负蝗Atractomorpha sinensis成虫的马氏管进行了观察,发现两者在着生位置、方式和细胞结构上存在明显不同.着生位置上,黄脸油葫芦的马氏管着生在后肠前端与后肠后端的交界处,短额负蝗的马氏管着生在中肠与后肠的交界处.着生方式上,黄脸油葫芦的马氏管是通过一根无色透明的公共管与肠道相通的,而短额负蝗的马氏管分为12丛,每一丛直接与肠道相连.细胞结构上,黄脸油葫芦的管壁由8个细胞构成,且集中在管的中央,与管壁有空隙;而短额负蝗的管壁由3～4个细胞组成,分散在管壁外围,有马氏管凸.     

黄脸油葫芦消化道和马氏管的组织学观察

应用石蜡切片技术对黄脸油葫芦Teleogryllus emma(Ohmachi and Matsumura)成虫消化道和马氏管的显微结构进行观察。消化道由前肠、中肠和后肠3部分组成:前肠由内向外可分为6层:内膜、肠壁细胞层、底膜、纵肌、环肌和围膜;中肠组织结构也分为6层,即由内向外依次为围食膜、肠壁细胞层、底膜、环肌、纵肌和围膜;后肠的组织结构与前肠基本相似,但内膜比前肠的薄,且肌肉的排列较前肠不规则,与中肠的肌肉排列相似,即环肌在内,纵肌在外。消化道各部位的结构差异与功能有密切关系。马氏管管壁由8个左右形状多变并具有显著细胞核的大形的单层上皮细胞组成。     

Water and ion regulation in cicadas in relation to xylem feeding

Cicadas feed on xylem fluid. This is hypotonic to the haemolymph and contains high concentrations of potassium, sodium, calcium, magnesium, chloride, and phosphate ions. The urine contains the same ions in the same proportions but in slightly lower concentrations. Amino acids and sucrose are present in xylem fluid and traces of amino acids are also found in urine.Water is rapidly shunted from foregut to hindgut via the filter chamber. Injection of xylem fluid into the oesophagus results in an immediate tenfold increase in flow rate in the ileum. The osmotic pressure of xylem fluid in the filter chamber rapidly rises whilst the osmotic pressure in the anterior part of the ileum rapidly falls.Absorption of nutrients and ions into the haemolymph probably occurs in the conical segment and anterior tubular midgut. Storage excretion of divalent ions occurs in the mid-midgut and ions may be transported from the haemolymph into the posterior tubular midgut.The Malpighian tubules secrete a fluid slightly hypertonic to blood containing K⁺ (42 mM/l.] and Na⁺ (14 mM/l.).The osmotic pressures within the internal Malpighian tubules and internal midgut in the filter chamber are considerably higher than the osmotic pressure of the xylem fluid when it first enters the filter chamber proper. Passive osmosis will occur and water will be shunted into the ileum.Reabsorption of K⁺ and Na⁺ occurs in the ileum.     

Serotonin-immunoreactive visceral nerves and neurohemal system in the cockroach Periplaneta americana (L.)

Summary By use of the indirect immunofluorescent technique applied to whole mounts of tissues and organs of the American cockroach, Periplaneta americana, serotonin-like reactivity has been demonstrated in an extensive meshwork of fibers on the surface of nerves of the subesophageal ganglion and the tritocerebrum. This meshwork appears to serve the neurohemal release of serotonin. In addition, several of these nerves contain two or more centrally located axons that appear to be serotonergic. The corpora cardica show immunoreactivity but do not appear to be a principal release site for serotonin. The nerves and ganglia of the stomadeal nervous system show immunoreactivity for serotonin and provide serotonin-positive innervation to the salivary glands and the visceral muscles of the stomodeum and midgut. The heart, hindgut, Malpighian tubules, fat body, and skeletal muscles all appear to lack serotonin immunoreactivity.     

Terminal versus segmental development in the Drosophila embryo: the role of the homeotic gene fork head

Summary Mutations of the homeotic gene fork head (fkh) of Drosophila transform the non-segmented terminal regions of the embryonic ectoderm into segmental derivatives: Pre-oral head structures and the foregut are replaced by post-oral head structures which are occasionally associated with thoracic structures. Posterior tail structures including the hindgut and the Malpighian tubules are replaced by post-oral head structures associated with anterior tail structures. The fkh gene shows no maternal effect and is required only during embryogenesis. The phenotypes of double mutants indicate that fkh acts independently of other homeotic genes (ANT-C, BX-C, spalt) and caudal. In addition, the fkh domains are not expanded in Polycomb (Pc) group mutant embryos. Ectopic expression of the homeotic selector genes of the ANT-C and BX-C in Pc group mutant embryos causes segmental transformations in terminal regions of the embryo only in the absence of fkh gene activity. Thus, fkh is a region-specific homeotic rather than a selector gene, which promotes terminal as opposed to segmental development. Offprint requests to: Institut für Biologie II (Genetik), Universität Tübingen, Auf der Morgenstelle 28, D-7400 Tübingen, Federal Republic of Germany