Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress
Giardini Naxos, Italy - 18/21 September, 2002
AcMNPV chi a protein produced in E. coli is potentially useful for plant defence
ARCIELLO S.*, FIANDRA L.**, GIORDANa B.**, de EGUILEOR M.***, RAO R.*
*) Dip. di Scienze del Suolo, della Pianta e dell’Ambiente, Università di Napoli “Federico II”, Via Università 100, 80055 Portici, Napoli
**) Dip. di Biologia. Università di Milano, Via Celoria 26, 20133 Milano
***) Dip. di Biologia Strutturale e Funzionale, Università dell’Insubria, Via Dunant 3, 21100 Varese
Protein purification, fungi toleration, peritrophic membrane perforation
Crop protection from pathogen organisms results crucial for modern agriculture. Fungus and insect damages represent the main cause of loss of production in agriculture (around 40%). Pest control, actually, is achieved through chemical pesticides determining problems of residues and environmental safety. The genetic engineering of plants to produce crops that are more resistant to insect pests or fungal pathogens indicates that biological control agents can play a larger role in integrated pest management and reduce our dependence upon chemical pesticides. However the onset of pesticide resistances in the target organisms has emphasized the need for more selective and effective molecules. Among the genes that can be used to protect plants from pathogen and pest infections, the best characterized genes are those that encode the hydrolytic enzymes known as chitinases. These hydrolytic enzymes inhibit the growth of many fungi in vitro by hydrolyzing the chitin and b-glucan of fungal cell walls. Furthermore, oligomeric products of digested chitin and b-glucan can act as signal molecules to stimulate further defense responses. These lytic enzymes have attracted much attention and have become very important resources in the genetic engineering of crop plants for both insect and fungi resistances.
The Multiple Nuclear Polyedrosis Virus of Autographa californica (AcMNPV) have developed mechanisms to digest the insect host peritrophic membrane in order to increase viroid penetration within the hosts. A chitinase gene (chi A) has been identified within the AcMNPV genome and several independent studies suggested that this gene might have a role in the host liquefaction (Hawtin et al., 1997). AcMNPV chi A gene has been cloned and expressed in E. coli and the purified protein proved to be active against the two pathogen fungi, Alternaria alternata and Botrytis cinerea. The protein was also tested in vitro on peritrophic membranes isolated from Bombyx mori larvae and proved to modify the permeability and to perforate the membrane as observed at the electron microscopy.
The results of this study provided evidences that chi A protein might be used as an alternative fungicide and /or biopesticide which allows crop protection from different biotic stresses, alone or in combination with other molecules.