Toxicity and mode of action of fungal lectins in pest insects important in agriculture

The urgent need for more and safer agricultural products, especially food, is rapidly increasing due to an increase of the global human population. Agriculture has suffered from multiple problems, a major threat being insects. These insects have been controlled with different methods mainly by using chemical insecticides. But many problems are associated with the use of these insecticides pushed entomologists to develop alternative methods for these chemical insecticides. Many plant lectins have been reported to possess insecticidal properties but very little is known about the entomotoxic effects of fungal lectins. The main objective of this PhD thesis is to study the insecticidal activity of fungal lectins isolated from two basidiomycetes namely Rhizoctonia solani and Sclerotinia sclerotiorum towards different pest insects and insect cell lines and to investigate the mode of action of these lectins. In vivo assays showed that these lectins have strong insecticidal activity towards pea aphid (Acyrthosiphon pisum) and cotton leafworm (Spodoptera littoralis). While in vitro assays using insect cell lines showed that the activity of these lectins depends on apoptosis induction or inhibition of cell proliferation. These findings suggest that fungal lectins are interesting tool that can be used for bioengineering insect resistance in important agronomical crops.