Impact of 1-MCP and Controlled Atmosphere on Physiological Disorders in Stored Pome Fruit: Biochemical Signatures of Oxidative Stress Metabolism

在气调贮藏中，作为降温的补充，通过控制氧气和二氧化碳分压来降低仁果果实的代谢活性。最佳条件是：(I)保持坚固性/品质；(Ii)促进复温期间的均匀成熟；以及(Iii)最大限度地减少可能导致经济损失的生理性贮藏障碍的发生率，如烫伤和内部褐变。CA条件可能导致细胞水平的氧化和还原(氧化还原)过程之间的失衡，并导致内源抗氧化剂(如抗坏血酸、NADPH)的损失和氧化应激代谢产物的积累，如伽马氨基丁酸酯(GABA)和伽马羟丁酸酯(GHB)。在这项建议中，我们打算调查氧化还原和GABA代谢的变化是否在时间上与在气调条件下贮藏的梨和苹果的外部伤害和果肉褐变有关。此外，用1-甲基环丙烯或1-甲基环丙烯等贮藏前化学物质处理仁果，旨在通过抑制乙烯介导的成熟来保持果实的品质，可能会影响氧化应激代谢。氧化还原对和应激代谢产物将通过反相高效液相色谱、GC-MS和UV/Vis分光光度测定，作为储存时间和1-MCP处理的函数。此外，我们还打算利用一个快速开花系来研究GHb的产生作为苹果果实生理障碍的先兆的相对重要性。该快速开花系是利用GHb形成酶--羟乙酰/琥珀酸半醛还原酶的RNAi结构转化的。该项目应有助于更好地了解造成苹果和梨贮藏过程中生理失调的机制，并有助于改进维持产品质量的贮藏规程，开发用于评估伤害潜力的诊断/技术，以及用于改善贮藏期间生理失调的基因工程策略。

In controlled atmosphere (CA) storage, the metabolic activity of pome fruit is decreased by controlling the oxygen and carbon dioxide partial pressures, as a supplement to a reduction in temperature. The optimal conditions are a compromise among: (i) maintaining firmness/quality; (ii) promoting uniform ripeness during re-warming; and, (iii) minimizing the incidence of physiological storage disorders such as scald and internal browning which can cause economic loss. CA conditions can result in an imbalance between oxidative and reductive (redox) processes at the cellular level and in the loss of endogenous antioxidants (e.g. ascorbate, NADPH) and accumulation of oxidative stress metabolites, like gamma-aminobutyrate (GABA) and gamma-hydroxybutyrate (GHB). In this proposal, we intend to investigate whether the shifts in redox and GABA metabolism are temporally associated with external injury and flesh browning in pears and apples stored under controlled atmosphere conditions. In addition, treatment of pome fruit with pre-storage chemicals, such as 1-methylcyclopropene or 1-MCP, aimed at preserving fruit quality via inhibition of ethylene mediated ripening may influence oxidative stress metabolism. The redox pairs and stress metabolites will be determined as a function of storage time and 1-MCP treatment via reverse-phase HPLC, GC-mass spectrometry, and with UV/Vis spectrophotometry. Also, we intend to investigate the relative importance of GHB production as a precursor to physiological disorders in apple fruit using a rapid-flowering line transformed with RNAi constructs of the GHB-forming enzyme, glyxoylate/succinic semialdehyde reductase. This project should lead to improved understanding of the mechanisms responsible for physiological disorders in stored apples and pears, and could contribute to improved storage protocols for maintaining quality of product, and the development of diagnostics/technologies for assessing injury potential and genetic engineering strategies for ameliorating physiological disorders during storage.