Tarlochan Dhadialla - Academia.edu (original) (raw)

Papers by Tarlochan Dhadialla

Pest Management Science, 2001

A series of insecticidal dihydropyrazoles and related compounds have been shown to exhibit negati... more A series of insecticidal dihydropyrazoles and related compounds have been shown to exhibit negative cross-resistance to a resistant (super-kdr) strain of houseflies with site-insensitivity to pyrethroids. The level of cross-resistance is similar to that observed previously for a range of N-alkylamides against the same strain.

Journal of Medical Entomology, Mar 1, 1988

ABSTRACT

Acs Symposium Series, Mar 19, 1997

Pesticide Science, Mar 1, 1999

ABSTRACT The non-steroidal, bis-acylhydrazine agonists of the insect molting hormone, 20-hydroxye... more ABSTRACT The non-steroidal, bis-acylhydrazine agonists of the insect molting hormone, 20-hydroxyecdysone, were first discovered over ten years ago. An extensive structure–activity optimization program yielded one commercial insecticide, tebufenozide (RH-5992) and two additional candidate insecticides (methoxyfenozide and halofenozide) which are in development. Tebufenozide is highly selective for lepidopteran pest control and is thus useful for IPM and resistance management programs. Methoxyfenozide (RH-2485) is also lepidopteran-selective but significantly more potent than tebufenozide and offers control of a wider range of lepidopteran pests. Halofenozide (RH-0345) is generally less potent and selective than tebufenozide or methoxyfenozide. However, its physical and biological properties make it well suited for control of beetle grubs and caterpillars in the soil. Target pest selectivity, new and novel mode of action, ecotoxicological safety and safety to beneficial arthropods make these insecticides valuable tools for integrated pest and resistance management programs.© 1999 Society of Chemical Industry

A thesis submitted to the Department of Biology in conformity with the requirements for the degre... more A thesis submitted to the Department of Biology in conformity with the requirements for the degree of Doctor of Philosophy

Insect Biochemistry, 1990

The patterns of protein synthesis by the milk gland and the fat body of female Glossina pallidipe... more The patterns of protein synthesis by the milk gland and the fat body of female Glossina pallidipes during the pregnancy cycle were studied by incubation with [35 S]methionine both/n vivo and in vitro. The pattern of protein synthesis by the milk gland changed with the stage of the larva in the uterus. Very little synthesis occurred in the milk gland until the first instar larva hatched. Then four proteins (13, 16, 24 and 72 kDa) were prominently synthesized. As the larva matured, the synthesis of 19, 38, 40 and 72 kDa proteins increased, whereas that of the 13 and 24 kDa proteins decreased. Just before larviposition, only the 16 and 72 kDa proteins were still being synthesized. The milk gland secreted into the medium primarily the 13, 16, 19 and 72 kDa proteins, all of which were found in the larval gut after a 5 hr pulse of labeled methionine in vivo. During most of the pregnancy cycle protein synthesis in the fat body was low compared to that of the milk gland and only small amounts of several low molecular weight proteins (less than or equal to 16 kDa) were released into the medium. But when a large third instar larva was present in the uterus, the fat body synthesized and secreted a 72 kDa and a 15-17 kDa complex of proteins.

Methods in molecular biology, Nov 11, 2018

Biotechnology has been central for the acceleration of crop improvement over the last two decades... more Biotechnology has been central for the acceleration of crop improvement over the last two decades. Since 1994, when the first commercial biotechnology-derived tomato crop was commercialized, the cultivated area for genetically modified crops has reached 185.1 million hactares worldwide. Both the number of crops and the number of traits developed using biotechnology have accounted for this increase. Among the most impactful biotechnology-derived traits are insect resistance and herbicide tolerance, which have greatly contributed to the worldwide increase in agricultural productivity and stabilization of food security. In this chapter, we provide an overview of the history of the biotechnology-derived input traits, the existing genetically engineered commercial crop products carrying insect resistance and herbicide tolerance traits, as well as a perspective on how new technologies could further impact the development of new traits in crops. With the projection of the world population to increase to 9.8 billion by the year 2050 and reduction in available farmland, one of the biggest challenges will be to provide sustainable nourishment to the projected population. Biotechnology will continue to be the key enabler for development of insect resistance and herbicide tolerance traits to overcome that imminent challenge.

Elsevier eBooks, 2012

Since the initial suggestion of using insect hormones or their mimics as the third-generation ins... more Since the initial suggestion of using insect hormones or their mimics as the third-generation insecticides, great strides have been made in the discovery of three classes of such insect growth-disrupting insecticides. We propose the use of the term “insect growth disruptors” instead of the mis-named term “insect growth regulators”. We review the commercial insecticides that mimic the mode of action of the insect growth and development hormones, the sesquiterpenoid juvenile hormones and the steroidal 20-hydroxyecdysone and the third class of insecticides that disrupt growth and development by interfering with chitin synthesis in target insect pests. In this chapter, the emphasis is on the application of these insecticides to control insect pests and development of resistance. Since the non-steroidal ecdysone agonist insecticides have been extensively reviewed in other chapters of this volume and elsewhere, only salient features of these novel insecticides are discussed.

Developmental Biology, Sep 1, 1987

Levels of vitellogenin (Vg) mRNA in Locusta migratoria fat body were determined as indicators of ... more Levels of vitellogenin (Vg) mRNA in Locusta migratoria fat body were determined as indicators of gene expression induced by the juvenile hormone analog methoprene. After injection of methoprene into juvenile hormone-deprived locusts, excised fat bodies were cultured with [3H]leucine for immunochemical assay of Vg synthesis, and RNA was assayed for Vg mRNA content by hybridization with probes from the previously cloned locust Vg genes A and B. In general, the rise in Vg mRNA paralleled the rise in Vg synthesis. During the primary response to methoprene (in female locusts in which the corpora allata had been destroyed immediately after emergence), Vg mRNA was first detected after 18-24 hr and accumulated rapidly between 36 and 48 hr. The secondary response (in locusts allatectomized during vitellogenesis and kept until Vg disappeared) was accelerated, as Vg mRNA was detectable at 12 hr and titers rose steeply after 18 hr. When Vg synthesis was prematurely induced by injection of methoprene into fifth-stage female larvae, the kinetics of mRNA accumulation were similar to those of primary stimulation in the adult. After allatectomy of vitellogenic females, fat body Vg mRNA decayed with a half-life of about 24 hr, roughly paralleling the decline in Vg synthesis. Assays with the two Vg probes showed coordinate accumulation of gene A and gene B messages under all conditions tested: during primary and secondary stimulation in adult females and in the low-level response obtained by treating male larvae with methoprene.

Zeitschrift für Parasitenkunde, 1990

Resistance to the hard tick, Rhipicephalus appendiculatus, was induced in rabbits by immunizing t... more Resistance to the hard tick, Rhipicephalus appendiculatus, was induced in rabbits by immunizing them with tick tissue proteins extracted with a detergent, Triton X-100. There was 25% mortality in female ticks fed on immunized rabbits as compared with those fed on controls. Similarly, there was a 40% and 60% reduction in the engorged weight and the weight of egg batches, respectively, of ticks fed on immunized rabbits. Western blot analysis of detergent-solubilized tick tissue proteins, carried out using immune sera, recognized a complex pattern of proteins. A strong reaction was observed with proteins with apparent molecular weights of 94000 and 40000 daltons.

Archives of Insect Biochemistry and Physiology, 1991

The presence of specific receptors for vitellogenin (Vg) in ovary membranes of the mosquito, Aede... more The presence of specific receptors for vitellogenin (Vg) in ovary membranes of the mosquito, Aedes aegypti, was demonstrated by an in vitro binding assay. The binding reaction, which is dependent on pH and Ca2+, uses 4 micrograms membrane protein, 35S-Vg labeled metabolically by fat body culture in vitro, and unlabeled vitellin (Vn) for competition. At pH 7.0 and in the presence of 5 mM Ca2+, the binding of Vg to its receptor reaches equilibrium within 60-90 min at both 4 and 25 degrees C. The binding is specific to membranes prepared only from ovaries. While mosquito Vg and Vn bind with equal affinity to Vg receptors on ovary membranes, neither locust Vg nor mouse IgG has any measurable affinity towards these sites. Nonlinear least square analysis of the saturation isotherms is consistent with the presence of a single class of Vg receptors on ovary membranes with a dissociation constant (Kd) of 0.18 microM.

Advances in Insect Physiology, 2014

This volume of Advances in Insect Physiology contains comprehensive interdisciplinary reviews on ... more This volume of Advances in Insect Physiology contains comprehensive interdisciplinary reviews on basic and practical aspects relevant to Insect Midgut and Insecticidal Proteins. * Contains important, comprehensive and in-depth reviews* An essential reference source for invertebrate physiologists and neurobiologists, entomologists, zoologists, and insect biochemists* First published in 1963, this serial is ranked second in the highly competitive ISI category of Entomology

International journal of invertebrate reproduction and development, Sep 1, 1987

Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Jan 24, 2012

Pesticide Science, Sep 1, 1998

Abstract: Toxicity assays with tebufenozide, the Ðrst commercial non-steroidalecdysteroid agonist... more Abstract: Toxicity assays with tebufenozide, the Ðrst commercial non-steroidalecdysteroid agonist, against a laboratory strain of the beet armyworm, Spodop-tera exigua (Hu” bner), demonstrated the promise of this new compound for thecontrol of this important pest. Experiments to select insects artiÐcially from thelaboratory strain by continuous exposure of larval instars to corresponding LC25doses of tebufenozide for over 12 generations 14(G E15 months),0]G12:revealed no loss in susceptibility to the insecticide for up to Ðve generations.Moreover, retention and fate of 14C-labelled tebufenozide were investigatedusing larvae from the selection experiments and the results compared withG6those for the susceptible larvae. In addition, piperonyl butoxide, an inhibitor(G0)of monooxygenases, when ingested by larvae along with tebufenozide, increasedthe susceptibility of intoxicated larvae to this ecdysteroid agonist, indicating itsoxidative metabolism in Spodoptera larvae. 1998 Society of Chemical(Industry.Pestic. Sci., 54,27E34 (1998)Key words: Spodoptera exigua; tebufenozide; ecdysteroid agonist; toxicity;resistance

Developmental Biology, Apr 1, 1983

Juvenile hormone (JH)-dependent vitellogenin (Vg) synthesis in the fat body of Locustu migrutwiu ... more Juvenile hormone (JH)-dependent vitellogenin (Vg) synthesis in the fat body of Locustu migrutwiu is normally limited to sexually mature adult females. As a step toward examining the basis of this limitation, we have tested female and male locusts in a series of stages after the third larval molt for inducibility of Vg synthesis by the synthetic JH analog, methoprene. We find that in the fourth and fifth larval instars fat body of both sexes can be induced to produce Vg, but in the adult stage females respond strongly while no more than trace amounts can be induced in males. Quantitative assays show relative responsiveness in the order: adult female > fifth instar female > fifth instar male B adult male. During the fifth instar of both sexes, maximal vitellogenic response was obtained in midinstar. After the larval-adult ecdysis, female fat body was unresponsive during the first 4 days, then responsiveness increased and by Day 8 after ecdysis fat bodies were fully as competent to produce Vg as at Day 14, the usual maximum of the first vitellogenic cycle due to endogenous JH. Larval and adult female fat bodies implanted into male larvae are competent for Vg synthesis after metamorphosis, so that the differences between adult male and female cannot be imposed by the male milieu int&ieur during the larval-adult molt. In male and female precocious adults, produced by treatment of fourth instars with precocene, fat body responded to methoprene as in normal adults. We conclude that factors intrinsic to the fat body cells, determined early in development, are responsible for differential gene programing in males and females, which is partially expressed by the fifth instar but fully manifest only after a molt in the absence of JH.

Journal of Biological Chemistry, Jun 1, 1990

Vitellogenin (Vg), the hemolymph precursor to the major yolk protein in mosquitoes, is synthesize... more Vitellogenin (Vg), the hemolymph precursor to the major yolk protein in mosquitoes, is synthesized in the fat body of blood-fed females. Mosquito Vg consists of two subunits with Mr = 200,000 and 66,000. Here, we demonstrate that both the Vg subunits are first synthesized as a single precursor. The identity of this Vg precursor was confirmed by immunoprecipitation with subunit-specific monoclonal antibodies. In cell-free translation of fat body poly (A)+ RNA, the Vg precursor had Mr = 224,000 which increased to 240,000 in the presence of canine pancreatic microsomal membranes. A precursor with Mr = 250,000 was immunoprecipitated in microsomal fractions isolated from rat bodies. With in vitro pulse labeling, the 250-kDa precursor could be detected in homogenates of fat bodies from blood-fed mosquitoes only during the first few hours accumulation of the Vg precursor was achieved by an in vitro stimulation of Vg synthesis in previtellogenic fat bodies cultured with an insect hormone, 20-hydroxyecdysone. The 250-kDa precursor was glycosylated and to a much lesser degree phosphorylated. Treatment of fat bodies with tunicamycin yielded the precursor with Mr = 226,000 which was neither glycosylated nor phosphorylated. The reduction in molecular mass of the 250-kDa Vg precursor and of both mature Vg subunits combined was similar after digestion with endoglycosidase H, indicating that glycosylation is completed prior to cleavage of the Vg precursor. In vitro pulse-chase experiments revealed rapid proteolytic cleavage of the 250-kDa precursor to two polypeptides with Mr = 190,000 and 62,000 which transformed into mature Vg subunits of 200- and 66-kDa as the last step prior to Vg secretion. This last step in Vg processing was inhibited by an ionophore, monensin, and therefore occurred in the Golgi complex. Sulfation as an additional, previously unknown, modification of mosquito Vg was revealed by the incorporation of sodium [35S]sulfate into both Vg subunits. Since sulfation of Vg was predominantly blocked by monensin, the final maturation of Vg subunits in the Golgi complex is, at least in part, due to this modification.

Annual Review of Entomology, 1992

In insects, accumulation of yolk, or vitellogenesis, is a heterosynthetic pro cess, in which an e... more In insects, accumulation of yolk, or vitellogenesis, is a heterosynthetic pro cess, in which an extraovarian tissue, the fat body, produces yolk protein precursors (1, 92). Heterosynthetic vitellogenesis occurs even in the most primitive insects, the Apterygota (9, 10, 1 13). Only ...

Advances in Insect Physiology, 2012

The latest volume in this series contains articles on arachnid physiology and behavior. The paper... more The latest volume in this series contains articles on arachnid physiology and behavior. The papers in this special issue give rise to key themes for the future.

Insect Biochemistry, 1989

An in vitro assay was used to study the uptake of vitellogenin (VG) by oocytes of the mosquito, A... more An in vitro assay was used to study the uptake of vitellogenin (VG) by oocytes of the mosquito, Aedes aegypti. The VG, obtained from the culture of fat bodies/n vitro, was metabolically labeled to a high specific activity (3-6 x 105 cpm/# g) using [35 S]methionine. Purification of both VG and vitellin (VN) from ovaries was achieved with ion-exchange chromatography on DEAE-Sepharose CL-6B. In an optimized in vitro system, mosquito oocytes in intact ovaries maintained stable endocytotic activity for at least 4 h. The rate of VG uptake was maximal at pH 7.5. It declined at acid pH and ceased abruptly at pH 6.3. Accumulation of VG by mosquito oocytes demonstrated features of receptor-mediated endocytosis; i.e. temperature dependence, saturability, selectivity and tissue specificity. The uptake of V(3 was inhibited at 4°C with only 6% of uptake achieved at 27°C. At 24 h post-blood meal, uptake of VG by oocytes at 27°C, neared saturation with a VG concentration in the medium of 8 #g//zl. Saturation kinetics generated for VG endocytosis by these oocytes produced a Vm~ x = 3.2 #g/#l/h and an apparent Kupt~ke = 8.4 x 10-6 M. Ovaries accumulated 10 times the amount of VG compared to mouse IgG, while uptake of VN was 71.6% of that for VG, indicating that oocytes from Aedes are able to distinguish these proteins. Non-ovarian tissues, fat body and Malpighian tubules, accumulated both VG and IgG at equally low levels. During the vitellogenic cycle, the rate of V(3 uptake by oocytes showed a steep and linear increase between 6 and 24 h post-blood meal. The peak of VG uptake occurred between 24 and 30 h post-blood meal, followed by a precipitous decline and cessation of uptake by 36 h.