The effect of 1-methylcyclopropene (1-MCP) on biosynthesis of volatiles and fruit ripening in apple (Malus ×domestica Borkh.) was investigated using `Golden Delicious', `Jonagold', and `Redchief Delicious' fruit. Application of 1-MCP to `Golden Delicious' at the preclimacteric stage effectively inhibited ripening as determined by decreased expression of genes for 1-amino-1-cyclopropane carboxylic acid (ACC) oxidase (ACO), and ACC synthase, ACO protein content, climacteric ethylene production, respiration, and volatile ester biosynthesis. Exogenous ethylene applied after 1-MCP treatment did not induce ethylene production, respiration, or volatile production. Activity for alcohol acyltransferase, which catalyzes the final step in ester formation, was demonstrable for 1-MCP-treated fruit, indicating no strict limitation on ester formation is imposed by this enzyme and that ester formation in 1-MCP-treated apple fruit is at least partially limited by reduced substrate synthesis. Once volatile ester formation had been suppressed by 1-MCP, the recovery of volatile synthesis required ≈3 weeks for `Jonagold' and 4 weeks for `Delicious' when held in air at 22 °C. For the first 2 months of storage at 0 °C in air, `Jonagold' and `Delicious' required ≈3 weeks holding at 22 °C for volatile biosynthesis to initiate; after 5 months in refrigerated storage, volatile formation was evident at the time of removal from cold storage. For `Jonagold' fruit held in controlled atmosphere (CA) storage for 2, 5, and 7 months at 0 °C, at least 3 weeks holding at 22 °C were required for volatile formation to begin to recover. The maximal amount of volatile formation was reduced 50% by 1-MCP relative to nontreated control fruit. CA storage had a similar impact on maximal volatile formation. The marketing of 1-MCP-treated fruit soon after treatment might result in the delivery of fruit to the consumer with little likelihood of recovery of volatile ester formation prior to consumption.
Alejandra Ferenczi, Jun Song, Meisheng Tian, Konstantinos Vlachonasios, David Dilley, and Randolph Beaudry
Raymond Fung*, Chien Wang, David Smith, Kenneth Gross, Yang Tao, and Meisheng Tian
Methyl salicylate (MeSA) and Methyl jasmonate (MeJA) treatments increased chilling resistance of light red tomato (Lycopersicon esculentum cv. Beefsteak) and extended shelf life and fresh-cut quality. We previously showed induction of AOX expression by low temperature and that induction of AOX transcript by MeSA and MeJA is correlated with resistance against chilling injury in peppers. Here, we investigate tomato, which is genetically closely related to peppers and belongs to the same Solanaceae family. In particular, we used four EST tomato clones of AOX from the public database that belong to two distinctly related families, 1 and 2 defined in plants. Three clones designated as LeAOX1a, 1b and 1c and the fourth clone as LeAOX2. Probes for these four genes were designed and Southern blotting done to confirm that they do not cross-hybridize. We will present data from Southern, Northern hybridization and RT-PCR to show: (1) gene copy number of each of these AOX members in the tomato genome; (2) gene-specific expression profiles in response to MeSA and MeJA in cold stored tomato; and (3) the relative transcript abundance of these four AOX genes.