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Subba Reddy Palli

Other affiliations: Canadian Forest Service, Rohm and Haas, Bharathiar University  ...read more
Bio: Subba Reddy Palli is an academic researcher from University of Kentucky. The author has contributed to research in topics: Ecdysone receptor & Juvenile hormone. The author has an hindex of 58, co-authored 274 publications receiving 10301 citations. Previous affiliations of Subba Reddy Palli include Canadian Forest Service & Rohm and Haas.


Papers
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Journal ArticleDOI
TL;DR: The recently acquired knowledge on the capacity of Met to bind JH, which has been mapped to a particular ligand-binding domain, is summarized, thus establishing this bHLH-PAS protein as a novel type of an intracellular hormone receptor.
Abstract: The molecular action of juvenile hormone (JH), a regulator of vital importance to insects, was until recently regarded as a mystery. The past few years have seen an explosion of studies of JH signaling, sparked by a finding that a JH-resistance gene, Methoprene-tolerant (Met), plays a critical role in insect metamorphosis. Here, we summarize the recently acquired knowledge on the capacity of Met to bind JH, which has been mapped to a particular ligand-binding domain, thus establishing this bHLH-PAS protein as a novel type of an intracellular hormone receptor. Next, we consider the significance of JH-dependent interactions of Met with other transcription factors and signaling pathways. We examine the regulation and biological roles of genes acting downstream of JH and Met in insect metamorphosis. Finally, we discuss the current gaps in our understanding of JH action and outline directions for future research.

627 citations

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TL;DR: This study provides the first example of an effective RNAi response in insects after feeding ds RNA produced in bacteria, and suggests that the efficient induction of RNAi using bacteria to deliver dsRNA is a possible method for management of Colorado potato beetle.
Abstract: BACKGROUND: RNA interference (RNAi) is a breakthrough technology for conducting functional genomics studies and also as a potential tool for crop protection against insect pests. The major challenge for efficient pest control using RNAi in the field is the development of efficient and reliable methods for production and delivery of double-stranded RNA (dsRNA). In this paper, the potential of feeding dsRNA expressed in bacteria or synthesized in vitro to manage populations of Colorado potato beetle, Leptinotarsa decemlineata (Say) (CPB), was investigated. RESULTS: Feeding RNAi successfully triggered the silencing of all five target genes tested and caused significant mortality and reduced body weight gain in the treated beetles. This study provides the first example of an effective RNAi response in insects after feeding dsRNA produced in bacteria. CONCLUSION: These results suggest that the efficient induction of RNAi using bacteria to deliver dsRNA is a possible method for management of CPB. This could be also a promising bioassay approach for genome-wide screens to identify effective target genes for use as novel RNAi-based insecticides. Copyright © 2010 Society of Chemical Industry

366 citations

Journal ArticleDOI
TL;DR: Functional studies using both double-strand RNA (dsRNA) and reverse genetic approaches showed that CYP6BQ9 confers deltamethrin resistance, and it was found that unlike many P450 genes involved in insecticide resistance that were reported previously, CYP9 is predominantly expressed in the brain, a part of the central nervous system (CNS) containing voltage-gated sodium channels targeted by deltAMethrin.
Abstract: Cytochrome P450-mediated detoxification is one of the most important mechanisms involved in insecticide resistance. However, the molecular basis of this mechanism and the physiological functions of P450s associated with insecticide resistance remain largely unknown. Here, we exploited the functional genomics and reverse genetic approaches to identify and characterize a P450 gene responsible for the majority of deltamethrin resistance observed in the QTC279 strain of Tribolium castaneum. We used recently completed whole-genome sequence of T. castaneum to prepare custom microarrays and identified a P450 gene, CYP6BQ9, which showed more than a 200-fold higher expression in the deltamethrin-resistant QTC279 strain when compared with its expression in the deltamethrin-susceptible Lab-S strain. Functional studies using both double-strand RNA (dsRNA)-mediated knockdown in the expression of CYP6BQ9 and transgenic expression of CYP6BQ9 in Drosophila melanogaster showed that CYP6BQ9 confers deltamethrin resistance. Furthermore, CYP6BQ9 enzyme expressed in baculovirus metabolizes deltamethrin to 4-hydroxy deltamethrin. Strikingly, we also found that unlike many P450 genes involved in insecticide resistance that were reported previously, CYP6BQ9 is predominantly expressed in the brain, a part of the central nervous system (CNS) containing voltage-gated sodium channels targeted by deltamethrin. Taken together, the current studies on the brain-specific insect P450 involved in deltamethrin resistance shed new light on the understanding of the molecular basis and evolution of insecticide resistance.

254 citations

Journal ArticleDOI
TL;DR: Major challenges to widespread use of RNAi in insect pest management include variable RNAi efficiency among insects, lack of reliable dsRNA delivery methods, off-target and nontarget effects, and potential development of resistance in insect populations.
Abstract: The RNA interference (RNAi) triggered by short/small interfering RNA (siRNA) was discovered in nematodes and found to function in most living organisms. RNAi has been widely used as a research tool to study gene functions and has shown great potential for the development of novel pest management strategies. RNAi is highly efficient and systemic in coleopterans but highly variable or inefficient in many other insects. Differences in double-stranded RNA (dsRNA) degradation, cellular uptake, inter- and intracellular transports, processing of dsRNA to siRNA, and RNA-induced silencing complex formation influence RNAi efficiency. The basic dsRNA delivery methods include microinjection, feeding, and soaking. To improve dsRNA delivery, various new technologies, including cationic liposome-assisted, nanoparticle-enabled, symbiont-mediated, and plant-mediated deliveries, have been developed. Major challenges to widespread use of RNAi in insect pest management include variable RNAi efficiency among insects, lack of reliable dsRNA delivery methods, off-target and nontarget effects, and potential development of resistance in insect populations.

251 citations

Journal ArticleDOI
TL;DR: It is shown that JH and 20E have antagonistic effects on the induction of antimicrobial peptide genes in Drosophila melanogaster, suggesting that 20E and JH play major roles in the regulation of gene expression in response to immune challenge.
Abstract: Juvenile hormone (JH) and 20-hydroxy-ecdysone (20E) are highly versatile hormones, coordinating development, growth, reproduction and aging in insects. Pulses of 20E provide key signals for initiating developmental and physiological transitions, while JH promotes or inhibits these signals in a stage-specific manner. Previous evidence suggests that JH and 20E might modulate innate immunity, but whether and how these hormones interact to regulate the immune response remains unclear. Here we show that JH and 20E have antagonistic effects on the induction of antimicrobial peptide (AMP) genes in Drosophila melanogaster. 20E pretreatment of Schneider S2 cells promoted the robust induction of AMP genes, following immune stimulation. On the other hand, JH III, and its synthetic analogs (JHa) methoprene and pyriproxyfen, strongly interfered with this 20E-dependent immune potentiation, although these hormones did not inhibit other 20E-induced cellular changes. Similarly, in vivo analyses in adult flies confirmed that JH is a hormonal immuno-suppressor. RNA silencing of either partner of the ecdysone receptor heterodimer (EcR or Usp) in S2 cells prevented the 20E-induced immune potentiation. In contrast, silencing methoprene-tolerant (Met), a candidate JH receptor, did not impair immuno-suppression by JH III and JHa, indicating that in this context MET is not a necessary JH receptor. Our results suggest that 20E and JH play major roles in the regulation of gene expression in response to immune challenge.

220 citations


Cited by
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Journal Article
TL;DR: Schulz et al. as discussed by the authors investigated whether adult macrophages all share a common developmental origin and found that a population of yolk-sac-derived, tissue-resident macophages was able to develop and persist in adult mice in the absence of hematopoietic stem cells.
Abstract: Macrophage Development Rewritten Macrophages provide protection against a wide variety of infections and critically shape the inflammatory environment in many tissues. These cells come in many flavors, as determined by differences in gene expression, cell surface phenotype and specific function. Schulz et al. (p. 86, published online 22 March) investigated whether adult macrophages all share a common developmental origin. Immune cells, including most macrophages, are widely thought to arise from hematopoietic stem cells (HSCs), which require the transcription factor Myb for their development. Analysis of Myb-deficient mice revealed that a population of yolk-sac–derived, tissue-resident macrophages was able to develop and persist in adult mice in the absence of HSCs. Importantly, yolk sac–derived macrophages also contributed substantially to the tissue macrophage pool even when HSCs were present. In mice, a population of tissue-resident macrophages arises independently of bone marrow–derived stem cells. Macrophages and dendritic cells (DCs) are key components of cellular immunity and are thought to originate and renew from hematopoietic stem cells (HSCs). However, some macrophages develop in the embryo before the appearance of definitive HSCs. We thus reinvestigated macrophage development. We found that the transcription factor Myb was required for development of HSCs and all CD11bhigh monocytes and macrophages, but was dispensable for yolk sac (YS) macrophages and for the development of YS-derived F4/80bright macrophages in several tissues, such as liver Kupffer cells, epidermal Langerhans cells, and microglia—cell populations that all can persist in adult mice independently of HSCs. These results define a lineage of tissue macrophages that derive from the YS and are genetically distinct from HSC progeny.

1,673 citations

19 Nov 2012

1,653 citations

Journal ArticleDOI
TL;DR: The genomic changes that lead to amplification, overexpression, and coding sequence variation in the three major groups of genes encoding metabolic enzymes, i.e., cytochrome P450 monooxygenases (P450s), esterases, and glutathione-S-transferases (GSTs), are the focus of this review.
Abstract: Xenobiotic resistance in insects has evolved predominantly by increasing the metabolic capability of detoxificative systems and/or reducing xenobiotic target site sensitivity. In contrast to the limited range of nucleotide changes that lead to target site insensitivity, many molecular mechanisms lead to enhancements in xenobiotic metabolism. The genomic changes that lead to amplification, overexpression, and coding sequence variation in the three major groups of genes encoding metabolic enzymes, i.e., cytochrome P450 monooxygenases (P450s), esterases, and glutathione-S-transferases (GSTs), are the focus of this review. A substantial number of the adaptive genomic changes associated with insecticide resistance that have been characterized to date are transposon mediated. Several lines of evidence suggest that P450 genes involved in insecticide resistance, and perhaps insecticide detoxification genes in general, may share an evolutionary association with genes involved in allelochemical metabolism. Differences in the selective regime imposed by allelochemicals and insecticides may account for the relative importance of regulatory or structural mutations in conferring resistance.

1,642 citations

Journal ArticleDOI
01 Sep 1955-Nature
TL;DR: In this article, the authors present an analysis of development in the context of the World Wide Web, with a focus on the first three stages of the development process and the first stage of the Internet.
Abstract: Analysis of Development Edited by Prof Benjamin H Willier, Prof Paul A Weiss and Prof Viktor Hamburger Pp xii + 735 (Philadelphia and London: W B Saunders Company, 1955) 105s

1,245 citations

Journal ArticleDOI
TL;DR: A comparison of insect diapause with other forms of dormancy in plants and animals suggests that upregulation of a subset of heat shock protein genes may be one feature common to different types of dormancies.
Abstract: Environmental and hormonal regulators of diapause have been reasonably well defined, but our understanding of the molecular regulation of diapause remains in its infancy. Though many genes are shut down during diapause, others are specifically expressed at this time. Classes of diapause-upregulated genes can be distinguished based on their expression patterns: Some are upregulated throughout diapause, and others are expressed only in early diapause, late diapause, or intermittently throughout diapause. The termination of diapause is accompanied by a rapid decline in expression of the diapause-upregulated genes and, conversely, an elevation in expression of many genes that were downregulated during diapause. A comparison of insect diapause with other forms of dormancy in plants and animals suggests that upregulation of a subset of heat shock protein genes may be one feature common to different types of dormancies.

1,052 citations