natural-products-in-plant-pest-management

120 L.A. ShcherbakovaRegarding the application, general elicitors to plant protection, chitosan,arachidonic, salicylic and β-aminobutyric acids may be referred to as examplesof active ingredients that have been formulated and introduced intoagricultural practice as commercial biogenic non-protein inducers of plantresistance. For instance, a supplement of tomato growth substratum withchitosan suppressed the root rot caused by F. oxysporum f. sp. radicis-lycopersici(Lafontaine and Benhamou, 1996). Moreover, several chitosan formulationscollectively known as ‘chitozars’, which are effective against root rots,late blight and powdery mildew on cereals, potato and legumes, have beenincluded in biological protection systems of these crops in Russia. Amongprotein elicitors, bacterial harpins are the most important. Harpins (hypersensitivityresponse and pathogenicity) are components of a transport systemused by bacteria to transfer proteins through bacterial and plantmembranes. In the bacterial genome, harpins are products a hrp-gene cluster.One of the first harpins studied was HrpN, the product of hprN geneexpressed in E. amylovora. HrpN has been shown to be an acidic glycine-richthermostable protein with a molecular mass of 44 kDa that induces resistancein Arabidopsis (Wei and Beer, 1996). Harpin has been commercialized andmarketed as a product that enhances resistance of some field, ornamentaland vegetable crops to many diseases, and that stimulates plant growth andflowering.In the coming years, we can expect the agricultural use of other elicitorproteins for increasing plant resistance to diseases both by engineering ofplants containing elicitor protein genes and by exposure of plants to proteinelicitor-based products. Two bacterial proteins with plant-protecting activityare considered below as examples of very promising compounds for developingboth resistant transgenic crops and products for plant treatment.Cold shock protein CspD as an elicitor of disease resistance in plantsCold shock protein D (CspD) isolated from Bacillus thuringiensis culture brothis a thermostable low molecular weight protein (molecular mass 7.2 kDa).The B. thuringiensis gene encoding CspD was cloned and sequenced (CspD, #AY272058 in GenBank). Nucleotide and amino acid sequences of CspD showhigh homology with other bacterial CSPs (Dzhavakhiya et al., 2000, Krominaand Dzhavakhiya, 2004).CSPs are highly conserved proteins produced by various bacteria constitutivelyor in response to cold shock. They have also been studied in plants,e.g. in Arabidopsis, tobacco and wheat. CSPs are involved in cell growth andadaptation to low temperatures. They bind nucleonic acids and are consideredto be putative translation anti-terminators. Bacterial CPSs contain a specificconserved cold shock domain (CSD), which occurs in CSPs from otherorganisms. For instance, a fragment of high homology to bacterial CSD wasfound in a family of plant CSPs referred to as glycine-rich proteins (GRPs).Expression of grp-genes is dependent on the level of plant hormones (indolylacetic, salicylic, abscisic acids), illumination and the plant developmentphase, and is upregulated by cold and wounding. The synthesis of GRPs can