A transgenic approach to control hemipteran insects by expressing insecticidal genes under phloem-specific promoters

Abstract

The first generation transgenic crops used strong constitutive promoters for transgene expression. However, tissue-specific expression is desirable for more precise targeting of transgenes. Moreover, piercing/sucking insects, which are generally resistant to insecticidal Bacillus thuringiensis (Bt) proteins, have emerged as a major pests since the introduction of transgenic crops expressing these toxins. Phloem-specific promoters isolated from Banana bunchy top virus (BBTV) were used for the expression of two insecticidal proteins, Hadronyche versuta (Blue Mountains funnel-web spider) neurotoxin (Hvt) and onion leaf lectin, in tobacco (Nicotiana tabacum). Here we demonstrate that transgenic plants expressing Hvt alone or in combination with onion leaf lectin are resistant to Phenacoccus solenopsis (cotton mealybug), Myzus persicae (green peach aphids) and Bemisia tabaci (silver leaf whitefly). The expression of both proteins under different phloem-specific promoters resulted in close to 100% mortality and provided more rapid protection than Hvt alone. Our results suggest the employment of the Hvt and onion leaf lectin transgenic constructs at the commercial level will reduce the use of chemical pesticides for control of hemipteran insect pests.

Engineered action at a distance: Blood-meal-inducible paralysis in Aedes aegypti

“…This consideration is of particular importance to GPM strategies such as those described here which aim to limit any deleterious effect until after the density-dependent stage. Additionally, alternative arthropod-specific neuroactive effectors could be tested for increased penetrance, for example the spider [31] or sea anemone [32] toxins. A class of potentially highly potent but as yet unrealised neuroactive effectors are the endogenous insect neuropeptides [33].…”

Tying pest insects in knots: the deployment of spider‐venom‐derived knottins as bioinsecticides

“…Transgenes encoding the spider knottin Hv1a (or its close otholog ω‐hexatoxin‐Ar1a) have been engineered into cotton, tobacco (alone or as a fusion to thioredoxin, onion leaf lectin, or Cry1Ac), poplar (fused to a C‐terminal fragment of CryIAb), and Arabidopsis (as a fusion to GNA or luteovirus coat protein). Transgenic plants expressing Hv1a/Ar1a are more resistant to a diverse range of insect pests, including bollworms ( Helicoverpa armigera ) and leafworms ( Spodoptera littoralis ) on cotton, peach‐potato aphids ( Myzus persicae ) on Arabidopsis , gypsy moth ( Lymantria dispar ) on poplar, and peach‐potato aphids, bollworms, leafworms, and whiteflies ( Bemisia tabaci ) on tobacco. In addition, tobacco plants engineered to express Magi‐6, a 36‐residue knottin from venom of the hexathelid spider Macrothele gigas , have greater resistance to fall armyworms ( S. frugiperda ) …”

The Protease Inhibitor CI2c Gene Induced by Bird Cherry-Oat Aphid in Barley Inhibits Green Peach Aphid Fecundity in Transgenic Arabidopsis

“…The CaMV35S promoter directs expression to both phloem and other tissue in dicots [ 54 , 55 ] and the expectations from transformation with the rolC promoter was to distinguish effects mainly restricted to phloem tissue to those in other parts of the leaf. As an example, in an earlier report, tobacco and chickpea were transformed with a gene encoding a leaf agglutinin protein using either CaMV35S or rolC -directed expression and the effects evaluated with GPA nymphs (on tobacco) or Aphids craccivora nymphs (on chickpea) [ 56 ].…”