Trehalose increases the oxidative stress tolerance and biocontrol efficacy of Candida oleophila in the microenvironment of pear wounds

Abstract

Harvested fruit tissues produce reactive oxygen species (ROS) in response to wounding. ROS production is further elevated when biocontrol yeasts are introduced into the wounds, where they act as a bio-elicitor and this results in an environment in which the biocontrol yeast is subject to oxidative stress. In the present study, the effect of trehalose, a non-reducing disaccharide and a major reserve carbohydrate, on the level of oxidative stress tolerance of the biocontrol yeast Candida oleophila was examined in wounded pear fruits. Results indicated that the level of trehalose in C. oleophila yeast cells increased when they were cultured in a trehalose-containing medium. Exposure to a trehalose-medium and the increase in internal trehalose improved the adaptation of C. oleophila to the oxidative environment present in pear fruit wounds. Trehalose-treated cells exhibited a lower accumulation of ROS and mitochondrial impairment compared to untreated, control cells when they were introduced into wounded pear fruit. The trehalose treatment up-regulated the expression of antioxidant genes, including peroxisomal catalase and thioredoxin reductase, in yeast cells. Trehalose-treated yeast also exhibited a faster growth rate in pear wounds and greater biocontrol efficacy against blue mold (Penicillium expansum) and Alternaria rot (Alternaria alternata) than untreated, control yeast. These results support the premise that trehalose improves the biocontrol efficacy of C. oleophila via the activation of antioxidant defense systems which support a faster rate of growth of the yeast in wounds of pear fruit.