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Aedes Mosquitoes: The Universal Vector
Published in Jagriti Narang, Manika Khanuja, Small Bite, Big Threat, 2020
Annette Angel, Bennet Angel, Neelam Yadav, Jagriti Narang, Surender Singh Yadav, Vinod Joshi
Inside the hypopharynx, there is a salivary canal through which saliva flows. The saliva consists of many important proteins that include anticoagulant, vasodilating properties (Snodgrass, 1959). The digestive or alimentary canal consists of pharynx, esophagus, stomach divided into foregut, midgut, and hindgut, followed by intestine, rectum, and anus (Fig. 1.15). The nervous system consists of central, peripheral, and sympathetic systems with brain and ganglions connecting to all parts of the body (Fig. 1.16). On each side of the head is a compound eye consisting of hundreds of small units called ommatidia (Jirakanjanakit et al., 2008). The respiratory system includes spiracles on either side of the body, which open into tracheal trunks toward the inside of the body cavity (Mill, 1985, 1998; Sláma, 1999).
ras Genes in Drosophila melanogaster
Published in Juan Carlos Lacal, Frank McCormick, The ras Superfamily of GTPases, 2017
The Roughened (R) mutation of D. melanogaster is a dominant mutation that disrupts eye development. Flies heterozygous for the mutation have rough eyes due to irregular spacing and orientation between adjacent ommatidia. In addition, the R7 photoreceptor is missing in most of ommatidia. The eyes of homozygous flies are even rougher. The identical chromosomal location of Roughened and the Ras3 gene initiated a set of experiments designed to test the possibility that they are eventually the same gene.12 Sequence analysis of the Ras3 gene in wild-type and Roughened chromosomes, and in chromosomes containing revenants of Roughened, proved this assumption. Ras3 appears to be the Drosophila homolog of the human Rap1A and Rap1B genes. Out of the 184 amino acids of the rap1A protein, 87% are identical and 93% are conserved in Ras3. The Roughened mutation is a point mutation that changes a phenylalanine at position 157 (position 156 of human Ha-ras) to leucine, and the Roughened revenants are stop codons within the Ras3/Rap1 protein. The phenylalanine at 157 is one of the few residues conserved outside the GTP-binding region in all members of the ras superfamily.
Protein Phosphorylation
Published in Enrique Pimentel, Handbook of Growth Factors, 2017
The v-ros oncogene contained in the avian sarcoma virus (AVS) UR2 encodes an oncoprotein, v-Ros, which possesses intrinsic tyrosine kinase activity. The normal cellular counterpart of the v-ros oncogene is the c-ros proto-oncogene, which is present in the vertebrate genome and is closely related to the Src protein family and the insulin receptor tyrosine kinase.187 Sequence analysis of chicken-derived c-roscDNA predicts a transmembrane tyrosine kinase molecule composed of 2311 amino acids. The carboxyl terminus of the chicken c-Ros protein contains 58 amino acids that are not present in the v-Ros oncoprotein. The c-ros gene may represent the vertebrate counterpart of the sevenless gene of Drosophila,188,189 whose product functions as a tyrosine kinase receptor and is required for the induction of a predetermined precursor cell to differentiate into photoreceptor number seven in the ommatidium of the compound eye of the insect.190
Cystathionine β-synthase Deficiency Impairs Vision in the Fruit Fly, Drosophila melanogaster
Published in Current Eye Research, 2021
Marycruz Flores-Flores, Leonardo Moreno-García, Felipe Castro-Martínez, Marcos Nahmad
The Drosophila eye is composed of more than 750 hexagonal units known as ommatidia. Each ommatidium consists of eight photoreceptor neurons, four lens-secreting cone cells, and two primary pigment cells. At the periphery of this core, there are secondary and tertiary pigment cells that the ommatidium shares with each of its adjacent neighbors, as well as mechanosensory bristles.17 In each ommatidium, six photoreceptor neurons (R1–R6) surround the other two (R7 and R8), forming a rosette-type structure, called the rhabdomere.18,19 As in the human retina, these neurons in the fly are designed for light reception, allowing the organism to collect information from its surrounding environment. In the human eye, the lens is specialized in pattern recognition, whereas the compound eye in insects specializes in movement perception.20 Because each ommatidium has its own lens and they are really small, visual acuity in Drosophila is about 1% of that of the human eye.21,22
Nanoparticles as a potential teratogen: a lesson learnt from fruit fly
Published in Nanotoxicology, 2019
Bedanta Kumar Barik, Monalisa Mishra
Phenotypic alterations such as deformities in thorax (Figure 4(B)) over successive generations suggest the mutagenic property of various NPs (Vecchio et al. 2012). Oral intake of NP causes cytotoxicity and DNA damage to mid-gut cells and imaginal disc (Patel and Champavat 2014; Sabat et al. 2016). The phenotypic defect in the gut and imaginal disc is caused due to overexpression of stress genes such as catalase, glutathione, and superoxide dismutase (Posgai et al. 2011; Jovanović et al. 2016). Bristles development is controlled by gene achaete-scute complex (Georgiev and Gerasimova 1992) along with signal transduction pathways such as EGFR and Notch (Furman and Bukharina 2007). NPs are expected to alter the functioning of the above gene involved in this pathway and bring structural variation in bristle. Wing defects such as small-wing incomplete venation (Figure 4(C,D)) is a consequence of the toxic effect of HAp NP on wing imaginal disc (de Celis 2003). Abnormal wing venation pattern can be a result of a defect in posterior cross vein gene, bone morphogenetic protein (BMP) and Notch signalling pathways (de Celis 2003). Wing spots within the wing are observed after NP treatment (Figure 4(E,F)). Wingspot assay is a known marker to detect mutation (Demir et al. 2011). The presence of wing spot indicates Co NPs acting as a mutagen. Multiple wing hairs strain and flare-3 strain are taken as control for wing spot assay. Membrane destabilization, membrane potential loss of mitochondria, and increased oxidative and apoptotic activity of gut cells are also used as the marker of gut. NP alters the eye imaginal disc and causes various phenotypic defect in the eye (Figure 5). Eye shape is reduced by decreasing the number of ommatidia from the periphery. Splitted eye is also observed in certain cases.
The world of the identified or digital neuron
Published in Journal of Neurogenetics, 2018
Each photoreceptor of the six is a member of a single cell class and has a representative from each of the eye’s approximately 750 ommatidia (Ready et al., 1976). Along with other classes of Drosophila sensilla, photoreceptors are probably among the largest classes of identifiable neuron in the fly’s brain, relative for example to at least 1100, the approximate number of olfactory receptor neurons (Vosshall & Stocker, 2007). Such wiring precision is hardly likely to be the sole preserve of the photoreceptor neurons, however, but should also exist in their downstream target neurons, given that photoreceptor inputs are characterized by the precise spatiotemporal signals they provide to the rest of the visual system. Indeed, interneurons in the medulla to which the fly’s photoreceptors provide indirect input, establish synaptic connections with a comparable and corresponding precision. Thus, synapses of the columnar neurons, those that occupy all columns, one in each, vary little in number so that all synapses have a > 99% chance of belonging to a consistent connection. The few connections not reproduced in seven neighbouring columns are considered inconsistent connections which, it has been concluded (Takemura et al., 2015), are wiring errors. It is not clear whether these persist or are merely transient morphogenetic errors. An additional class of synaptic singularity are autapses, in which the same medulla neuron is presynaptic upon itself. This occurs at a relatively elevated rate (≥∼2%) but in only two medulla cells (Mi1 and Dm9), at least 20-fold more frequently in these than for other cell types (Takemura et al., 2015). A simple interpretation would be that the reduced rate of autapses for all other cell types reflects the baseline error in the fly’s ability to programme synaptogenesis, whereas in Mi1 and Dm9, the increased rate is functionally significant. But other interpretations are possible.