The sap sucking insects (Hemiptera), which include aphids, whiteflies, plant bugs and stink bugs, have emerged as major agricultural pests. The Hemiptera cause direct damage by feeding on crops, and in some cases indirect damage by transmission of plant viruses. Current management relies almost exclusively on application of classical chemical insecticides. While the development of transgenic crops expressing toxins derived from the bacterium Bacillus thuringiensis (Bt) has provided effective plant protection against some insect pests, Bt toxins exhibit little toxicity against sap sucking insects. Indeed, the pest status of some Hemiptera on Bt-transgenic plants has increased in the absence of pesticide application. The increased pest status of numerous hemipteran species, combined with increased prevalence of resistance to chemical insecticides, provides impetus for the development of biologically based, alternative management strategies. Here, we provide an overview of approaches toward transgenic resistance to hemipteran pests.

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Although transgenic crops expressing Bacillus thuringiensis (Bt) toxins have been used successfully for management of lepidopteran and coleopteran pest species, the sap-sucking insects (Hemiptera) are not particularly susceptible to Bt toxins. To overcome this limitation, we demonstrate that addition of a short peptide sequence selected for binding to the gut of the targeted pest species serves to increase toxicity against said pest. Insertion of a 12-aa pea aphid gut-binding peptide by adding to or replacing amino acids in one of three loops of the Bt cytolytic toxin, Cyt2Aa, resulted in enhanced binding and toxicity against both the pea aphid, Acyrthosiphon pisum, and the green peach aphid, Myzus persicae. This strategy may allow for transgenic plant-mediated suppression of other hemipteran pests, which include some of the most important pests of global agriculture.aphid management | biotechnology | insect resistance

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Insect-borne plant viruses cause significant agricultural losses and jeopardize sustainable global food production. Although blocking plant virus transmission would allow for crop protection, virus receptors in insect vectors are unknown. Here we identify membrane alanyl aminopeptidase N (APN) as a receptor for pea enation mosaic virus (PEMV) coat protein (CP) in the gut of the pea aphid, Acyrthosiphon pisum, using a far-Western blot method. Pulldown and immunofluorescence binding assays and surface plasmon resonance were used to confirm and characterize CP-APN interaction. PEMV virions and a peptide comprised of PEMV CP fused to a proline-rich hinge (-P-) and green fluorescent protein (CP-P-GFP) specifically bound to APN. Recombinant APN expressed in Sf9 cells resulted in internalization of CP-P-GFP, which was visualized by confocal microscopy; such internalization is an expected hallmark of a functional gut receptor. Viruses that infect crop plants restrict our ability to consistently produce high yields from agricultural crops. Many of these viruses are transmitted to plants by pestiferous insects, with aphids transmitting nearly half of the 600 insect-borne plant viruses. Aphids therefore represent a significant threat to global agriculture (1). Viruses in the family Luteoviridae are phloem-restricted RNA viruses transmitted exclusively by aphids and cause disease in multiple food crops (2). Luteovirids are transmitted in a circulative and persistent manner which involves specific molecular interactions between the virus and the aphid (3). For this type of transmission, ingested virions cross the aphid gut and salivary gland epithelial barriers for transmission to additional plant hosts.Luteovirus-aphid interactions are mediated by the viral capsid proteins consisting of a major coat protein (CP; 22 kDa) and one minor coat protein readthrough domain (CP-RTD; 35 to 55 kDa) (3). The RTD is not required for virus particle assembly or for uptake of virus from the gut into the aphid hemocoel, but both CP and RTD are essential for aphid transmission and are the sole determinants of vector specificity (3). The virus binds to a receptor in either the midgut, hindgut, or both for transcytosis across the aphid gut epithelium and release into the hemocoel (4). A second receptor-mediated transcytosis event occurs at the accessory salivary glands (ASG) from which virus particles are secreted with saliva to inoculate the plant phloem during subsequent feedings (5). Only a fraction of the virions present in the aphid hemolymph cross into the ASG, and a threshold amount of virus in the hemocoel is required before transmission via the ASG can occur (3). Hence, impeding the binding of a plant virus to the aphid gut receptor could reduce the amount of virus present in the hemocoel to less-than-threshold levels, thereby reducing plant virus transmission. Citation Linz LB, Liu S, Chougule NP, Bonning BC. 2015. In vitro evidence supports membrane alanyl aminopeptidase N as a receptor for a plant virus in the pea aphid ve...

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