Role of Climacteric Ethylene Production in Methyl Jasmonate-induced Green Loss in Orin Apples (original) (raw)
The effects of methyl jasmonate (JAMe) vapor on the peel coloring (loss of green and gain of yellow) in semi-matured and matured green apples (cultivar., Orin) before and after the initiation of the climacteric-rise in ethylene production was compared. In semi-mature apples (160 day-old, pre-climacteric stage) without endogenous ethylene production, no significant enhancement in de-greening, yellowing or the productions of ethylene and CO 2 was induced after treatment with JAMe vapor alone. Treatment of the pre-climacteric apples with exogenous ethylene initiated the burst of both ethylene biosynthesis and CO 2 emission, and enhanced the peel coloring (both de-greening and yellowing). The addition of both ethylene and JAMe to the pre-climacteric apples resulted in a further enhancement in the coloring, ethylene production and respiration when compared with the effect of ethylene alone. In mature apples during the post-climacteric phase of ethylene production (180 days after anthesis; ca. 60 µl ethylene produced per kgfw at day 0), a significant enhancement in de-greening by JAMe vapor was observed, although peel yellowing was no longer affected. The ethylene production and CO 2 emission were also enhanced by JAMe. These results suggest that the Orin apples are responsive to JAMe in a maturity-dependent manner in which initiation of the climacteric ethylene biosynthesis is the key factor.
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De-greening (loss of green color) in Citrus unshiu peel treated with 50 ppm ethylene and/or various concentrations of methyl jasmonate (JAMe) ranging from 0.5 µM to 5 mM, was determined by measuring the color changes using Hunter's colorimeter. De-greening in the fruit peel was markedly enhanced by ethylene. In the absence of ethylene, 5 mM JAMe also showed an enhancement of the de-greening to a slightly lesser extent. The emission of CO 2 was highly enhanced by 5 mM JAMe regardless of the presence or absence of ethylene, suggesting the elevated level of respiration or metabolism. Ethylene biosynthesis was transiently stimulated when both 5 mM JAMe and 50 ppm ethelene were added to the citrus. The effect of JAMe on the de-greening was inhibited by cycloheximide, but not by chloramphenicol, indicating the necessity of de novo protein synthesis in the cytosol for promoting the JAMe-dependent de-greening process. A marked increase in the chlorophyllase activity was induced by ethylene but not by JAMe. Therefore, an alternative de-greening mechanism may be involved in the JAMe-induced peel color change.
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