Impact of 1-MCP and controlled atmosphere on physiological disorders in stored apples: GABA and polyamine metabolism

目前，加拿大生产的新鲜市场苹果（农场门值为1.64亿美元）中约有30-40%用1-甲基环丙烯（1-MCP）处理，这有助于保持水果质量和延长保质期，从而增加市场机会。唯一的负面反应已增加某些苹果品种在气调贮藏（CA）期间对低温和CO2相关疾病的易感性。CA条件可导致细胞水平的氧化和还原过程之间的不平衡，以及称为γ-氨基丁酸（GABA）的代谢物的积累。虽然GABA积累是光合组织中对所有胁迫的众所周知的反应，但其作用以及与其在非光合组织中积累相关的机制在很大程度上尚未探索。在这个建议中，我们打算调查是否GABA和γ-羟基丁酸（GHB），一个密切相关的代谢产物，其积累是受氧化还原状态，和他们的潜在的前体（多胺与谷氨酸），与外部伤害和果肉布朗宁苹果从两个流行的加拿大品种（'帝国'和麦金托什'）。苹果将被储存在不同的CA条件下的温度和CO2与或没有1-MCP处理和代谢物的配置文件，以及水果的质量，将被确定为存储时间的函数，使用反相HPLC和质谱。此外，我们打算调查的相对重要性，多胺和谷氨酸衍生的GABA生产在苹果果实的生物化学（酶活性，示踪剂）和分子（基因表达）分析相结合。该项目将改善

Currently, about 30-40% of the fresh market apples produced in Canada (farm gate value of $164M) is treated with 1-methylcyclopropene (1-MCP), which helps to maintain fruit quality and extend shelf life, thereby increasing marketing opportunities. The only negative response has been increased susceptibility to low temperature- and CO2-related disorders in certain apple cultivars during controlled atmosphere (CA) storage. CA conditions can result in an imbalance between oxidative and reductive processes at the cellular level and in the accumulation of a metabolite called gamma-aminobutyrate (GABA). While GABA accumulation is a well known response to all stresses in photosynthetic tissues, its role and the mechanisms associated with its accumulation in non-photosynthetic tissues are largely unexplored. In this proposal, we intend to investigate whether GABA and gamma-hydroxybutyrate (GHB), a closely related metabolite whose accumulation is regulated by redox status, and their potential precursors (polyamines versus glutamate), are associated with external injury and flesh browning in apples from two popular Canadian cultivars ('Empire' and McIntosh'). The apples will be stored under various CA conditions of temperature and CO2 with or without 1-MCP treatment and metabolite profiles, as well as fruit quality, will be determined as a function of storage time using reverse-phase HPLC and mass spectrometry. Also, we intend to investigate the relative importance of polyamine- and glutamate-derived GABA production in apple fruit using a combination of biochemical (enzyme activities, tracer) and molecular (gene expression) analyses. This project should lead to improved