Pathogenesis Related Defence Functions of Plant Chitinases and β-1,3-Glucanases

Pathogenesis Related Defence Functions of Plant Chitinases and β-1,3-Glucanases

When resistant plants recognize cognate or matching elicitors, intracellular signal transduction pathways are activated that ultimately result in the derepression of a battery of genes called defence response genes. Besides alteration in several biochemical parameters leading to enhanced production of phytoalexins, deposition of callose, lignification etc., the pathogen attack is accompanied by production of several pathogenesis related (PR) proteins. However, only plant chitinases and β-1,3-glucanases have been extensively studied. Pathogenesis-related proteins including hydrolytic enzymes chitinases and β- 1,3-glucanases, have been known to be induced in plants upon infection with various pathogens. This in part is due to the immediate realization that these hydrolytic enzymes could degrade cell walls of certain fungi. These enzymes were shown to be induced in plants upon infection and some purified proteins were observed to have antifungal activity in vitro. Chitinases and glucanases have been purified and characterized from a number of plant sources. Expressions of gene encoding these enzymes have also been quantified from a variety of plant sources. Currently, there is an immense interest in delineating the molecular events from pathogen recognition to the expression of these genes. In an effort to enhance the disease resistance, PR-genes have been used to transform a variety of plant sources. There is considerable evidence showing positive correlation between the expression of PR-genes and disease resistance. The research work being carried out on the role of PR proteins in three important crop species, viz. Sorghum (Sorghum bicolor), rocket salad (Eruca sativa) and moth bean (Vigna aconitifolia) in response to infection by fungal pathogens have been examined...