Snowdrop lectin inhibits development and decreases fecundity of the Glasshouse Potato Aphid ( Aulacorthum solani) when administered in vitro and via transgenic plants both in laboratory and glasshouse trials

Abstract

The effects of snowdrop lectin ( Galanthus nivalis agglutinin, GNA) on the Glasshouse Potato Aphid ( Aulacothum solani) were tested by bioassays where the protein was incorporated into an artificial diet at a single concentration of 0.1% ( w v ). The results showed that the presence of GNA in the diet throughout the insect's life cycle decreased the fecundity of adult aphids, as measured by nymph production, by up to 65%, but normally caused only a marginal decrease (≤ 10%) in aphid survival. The deleterious effect of GNA was significantly reduced if insects were reared on control diet, and transferred to diet containing GNA at maturity. GNA was also shown to affect the development of nymphal aphids by measuring growth using image analysis software. The presence of GNA in the diet decreased the rate of increase in length and width of the aphids by up to 40%, and, in this assay, also caused high levels of mortality. GNA was expressed in potato plants, ( Solanum tuberosum L.) cv. Desirée, after transformation with a construct containing a gene encoding the protein driven by the CaMV 35S promoter. GNA expression levels in transgenic potato leaves were found to be in the range 0.3–0.4% of total soluble protein, as measured by immunodot blot analysis using polyclonal antibodies raised against the protein. Bioassays carried out under controlled environmental conditions, using clip cages, showed that the number of nymphs produced on these transgenic plants was significantly ( P < 0.01) reduced compared to that on non-transgenic control plants. The decrease in fecundity observed in this bioassay was similar to that seen in the artificial diet bioassays. Large scale glasshouse trials showed that the rate of population build-up on the GNA-expressing plants was approximately four-fold lower than on the control plants. These experiments demonstrate that the insecticidal effects of GNA observed in artificial diets can be reproduced in planta, both under laboratory bioassay conditions and in the glasshouse.