LOW TEMPERATURE DELAYS THE INDUCTION OF CHITINASE ISOENZYMES ASSOCIATED WITH ANTIFUNGAL ACTIVITY
In order to better understand the effects of low temperature on the active defense strategies used by cherimoya (Annona cherimola Mill.) fruit, antifungal activity and the induction of PR-3 pathogenesis-related proteins (chitinase family) were estimated in fruit stored at 6°C. During cherimoya ripening, the pattern of acidic and basic chitinase expression revealed that only the transiently induced isoenzymes were positively correlated with efficient antifungal defense mechanism. This developmentally regulated resistance operated in two successive phases: (1) the induction of acidic isoenzymes in ripe fruit; and (2) the release of basic isoenzymes by over-ripe fruit. We have studied the effect of low temperature storage on the induction of two of these isoenzymes, one acidic chitinase of 25.8 kDa (AChi26) and a basic one of 33.0 kDa (BChi33). Induction of AChi26 is associated with the enhanced antifungal activity of the acidic protein extract in ripe fruit and it was observed from the 3rd to 5th day of storage at 6°C. Likewise, the appearance of BChi33, which is generally correlated with the antifungal activity of the basic protein extract in over-ripe fruit, was delayed by low temperature storage, and it was only induced after 9 days of storage. Despite this delay, the induction of these transient chitinases was associated with significant antifungal activity in the acidic and basic protein extracts. These results suggest that the two successive defense phases and the effectiveness of this preventive defense strategy persist after low temperature storage.
Goñi, O., Sanchez-Ballesta, M.T., Merodio , C. and Escribano, M.I. (2012). LOW TEMPERATURE DELAYS THE INDUCTION OF CHITINASE ISOENZYMES ASSOCIATED WITH ANTIFUNGAL ACTIVITY . Acta Hortic. 934, 379-385
Annona cherimola, acidic and basic isoenzymes, amino acids, carbohydrates, defense proteins, ripening