Comparative studies on the lethal giant larvae gene in Ostrinia nubilalis (Lepidoptera: Pyralidae) and Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)

The western corn rootworm (WCR; Diabrotica virgifera virgifera) and the European corn borer (ECB; Ostrinia nubilalis) are key pests worldwide; each costing well over a billion dollars annually in the United States alone. Bt-corn, altered planning dates, and crop rotations are currently the main management strategies for controlling these pests; however, control is becoming progressively more challenging due to development of insecticide-, rotation-, and trait-resistant strains. Corn plants expressing dsRNA targeting WCR have been shown to significantly reduce larval damage, and this technology is actively being pursued. Unfortunately, no such RNAi-based technologies are currently being developed to combat ECB due to RNAi inefficiency associated with Lepidoptera. Given that coleopterans are well known for being highly amendable to RNAi and lepidopterans are not, we are interested in using a comparative approach to identify the factors limiting RNAi efficiency in ECB but not in WCR. As a first step we sequenced cDNA putatively encoding the lethal giant larvae (Lgl) protein from ECB and WCR for use as a reporter gene. Lgl plays an essential role in insect development and metamorphosis through establishment of apical-basal cell polarity, and control of cell proliferation, differentiation, and tissue organization. Lgl is regarded as highly conserved among insects and as being constitutively expressed in all life stages. Furthermore, Lgl is highly amendable to knockdown in Tribolium castaneum and results in mortality and developmental deformities when suppressed, making it ideal for use as a reporter gene. Here we present the sequence of Lgl cDNA for ECB and WCR, as well as discuses the conservation of the deduced amino acid sequences. These sequences are aligned with Lgl sequences from other species for investigation of the phylogenetic relationship of ECB and WCR Lgl to other Insect Lgls. This investigation provides insight into the conservation of Lgl in insects, and will facilitate our investigation of molecular mechanisms influencing RNAi efficiency in ECB and WCR, during which Lgl will be assessed for its utility as a target gene for the management of these two important pests.