Expression of the LePR5 gene from cherry tomato fruit induced by Cryptococcus laurentii and the analysis of LePR5 protein antifungal activity

Abstract

The biocontrol yeast Cryptococcus laurentii could induce disease resistance of cherry tomato fruit and significantly reduce black rot incidence. Previous research reported that LePR5 was up-regulated when postharvest cherry tomato fruit were treated by biocontrol yeast C. laurentii for 24h. LePR5, a defense related protein from cherry tomato fruit, belongs to the thaumatin-like proteins. The amino acid sequence and predicted protein model of LePR5 have all the reported structural elements that are presumed necessary for activity resistant to pathogens. Using real-time PCR analysis this study showed that LePR5 transcript levels were increased significantly after inoculation with Alternaria alternata and C. laurentii. The LePR5 expression level induced by A. alternata was significantly higher than by C. laurentii after 48h. Furthermore, LePR5 protein was produced and purified by using an Escherichia coli expression system and its refolded protein showed antifungal activity to A. alternata in vitro and in vivo. Finally, LePR5 protein treatment apparently controlled the disease incidence of black rot infection caused by A. alternata in cherry tomato fruit in a dose-dependant manner. These results suggest that LePR5 plays a role in the defense system of cherry tomatoes and is involved in the biocontrol mechanism involving yeast by inducing a resistance protein against pathogens in postharvest fruit.