Pathogenesis-related proteins of tea triggered by Exobasidium vexans

Abstract

The defense strategy of tea plants against Exobasidium vexans are multifold and include accumulation of pathogenesis-related (PR) proteins. A study on the association of defense enzymes with resistance in tea plants triggered by E. vexans revealed significant changes in the level of β-1.3-glucanase (PR 2) and chitinase (PR 3) exhibiting antimicrobial activity. Accumulation of defense proteins differed in time and magnitude. Time course studies points towards accumulation of PR-2 and PR-3 in the early hours, PR-9 later on and finally the antifungal metabolites that confer resistance to the plants. Treatment with salicylic acid (SA) stimulates a multicomponent defense response in tea leaves which was confirmed by immuno-localization of PR 2 and PR 3 in tea leaf tissues following induction of resistance. Induction of PR-3 in suspension-cultured tea cells following SA treatment was confirmed immunologically using antibody probes (PAb-chitnase). Subcellular localization of PR-3 and PR-2 in tea leaves were also confirmed by indirect immunogold labeling. Marked increase in frequency of gold particles following elicitation by SA treatment was evident. Cell defense responses associated with systemic acquired resistance induced by SA against E.vexans has been discussed in relation to the possible role of PR-proteins in immunizing tea plants.