Mechanism of PR gene expression by treatment of tobacco leaves with yeast extract (AGREVO EX).

Abstract

Application of AGREVO EX, a plant energizer made of yeast extract (YE), promotes root growth and suppresses plant diseases. Because no antimicrobial activity was found in the YE itself, YE induction of the plant's self-defense system has been suggested. To study the mechanism of enhanced disease resistance, the effect of YE on the expression of defense-related genes was analyzed in detached tobacco leaves. YE induced the expression of basic PR-1, -2, and -6 genes but not the acidic PR-1 gene. The YE solution itself produced ethylene, and ethylene emission from tobacco leaf discs was enhanced by the YE treatment. Also YE induced accumulation of PR-1, -2, and -3 proteins, and its suppression by treatment with silver thiosulfate (STS), which inhibits the perception of ethylene, suggesting the involvement of ethylene in YE-induced PR protein accumulation. The YE treatment did not induce resistance to Tobacco mosaic virus (TMV), but likely induced resistance to Ralstonia solanacearum and Rhizoctonia solani in tobacco plants, suggesting that YE may enhance resistance against necrotrophic pathogens.