A ribonucleic acid (RNA) interferer that operates, upon uptake by a species of insect pests by downregulating the expression of a target gene in said insect pest, wherein the interfering RNA comprises at least one silencing element in the said silencer element is a double stranded RNA region comprising hybridized complementary strands of which one strand comprises or consists of a sequence of at least 35 contiguous nucleotides that is at least 85% complementary to any of SEQ ID NO: 1 , 174, 180, 188, 2, 175, 181, 189 or the complement thereof.

Commercial biotechnology solutions for controlling lepidopteran and coleopteran insect pests on crops depend on the expression of Bacillus thuringiensis insecticidal proteins(1,2), most of which permeabilize the membranes of gut epithelial cells of susceptible insects(3). However, insect control strategies involving a different mode of action would be valuable for managing the emergence of insect resistance. Toward this end, we demonstrate that ingestion of doublestranded (ds)RNAs supplied in an artificial diet triggers RNA interference in several coleopteran species, most notably the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte. This may result in larval stunting and mortality. Transgenic corn plants engineered to express WCR dsRNAs show a significant reduction in WCR feeding damage in a growth chamber assay, suggesting that the RNAi pathway can be exploited to control insect pests via in planta expression of a dsRNA.

Ras signaling has been shown to play an important role in promoting cell survival in many different tissues. Here we show that upregulation of Ras activity in adult Drosophila neurons induces neuronal cell death, as evident from the phenotype of vacuolar peduncle (vap) mutants defective in the Drosophila RasGAP gene, which encodes a Ras GTPase-activating protein. These mutants show age-related brain degeneration that is dependent on activation of the EGF receptor signaling pathway in adult neurons, leading to autophagic cell death (cell death type 2). These results provide the first evidence for a requirement of Egf receptor activity in differentiated adult Drosophila neurons and show that a delicate balance of Ras activity is essential for the survival of adult neurons.

Mammalian Ras GTPase-activating protein (GAP), p120 Ras-GAP, has been implicated as both a downregulator and effector of Ras proteins, but its precise role in Ras-mediated signal transduction pathways is unclear. To begin a genetic analysis of the role of p120 Ras-GAP we identified a homolog from the fruit fly Drosophila melanogaster through its ability to complement the sterility of a Schizosaccharomyces pombe (fission yeast) gap1 mutant strain. Like its mammalian homolog, Drosophila RasGAP stimulated the intrinsic GTPase activity of normal mammalian H-Ras but not that of the oncogenic Val12 mutant. RasGAP was tyrosine phosphorylated in embryos and its Src homology 2 (SH2) domains could bind in vitro to a small number of tyrosine-phosphorylated proteins expressed at various developmental stages. Ectopic expression of RasGAP in the wing imaginal disc reduced the size of the adult wing by up to 45% and suppressed ectopic wing vein formation caused by expression of activated forms of Breathless and Heartless, two Drosophila receptor tyrosine kinases of the fibroblast growth factor receptor family. The in vivo effects of RasGAP overexpression required intact SH2 domains, indicating that intracellular localization of RasGAP through SH2-phosphotyrosine interactions is important for its activity. These results show that RasGAP can function as an inhibitor of signaling pathways mediated by Ras and receptor tyrosine kinases in vivo. Genetic interactions, however, suggested a Ras-independent role for RasGAP in the regulation of growth. The system described here should enable genetic screens to be performed to identify regulators and effectors of p120 Ras-GAP.

In Drosophila, specification of embryonic terminal cells is controlled by the Torso receptor tyrosine kinase. Here, we analyze the molecular basis of positive (Y630) and negative (Y918) phosphotyrosine (pY) signaling sites on Torso. We find that the Drosophila homolog of RasGAP associates with pY918 and is a negative effector of Torso signaling. Further, we show that the tyrosine phosphatase Corkscrew (CSW), which associates with pY630, specifically dephosphorylates the negative pY918 Torso signaling site, thus identifying Torso to be a substrate of CSW in the terminal pathway. CSW also serves as an adaptor protein for DRK binding, physically linking Torso to Ras activation. The opposing actions of CSW and RasGAP modulate the strength of the Torso signal, contributing to the establishment of precise boundaries for terminal structure development.