Department of Plant Agriculture, University of Guelph Guelph, ON, Canada.
Front Plant Sci. 2014 Apr 10;5:144. doi: 10.3389/fpls.2014.00144. eCollection 2014.
1-Methylcyclopropene (1-MCP) delays ethylene-meditated ripening of apple (Malus domestica Borkh.) fruit during controlled atmosphere (CA) storage. Here, we tested the hypothesis that 1-MCP and CA storage enhances the levels of polyamines (PAs) and 4-aminobutyrate (GABA) in apple fruit. A 46-week experiment was conducted with "Empire" apple using a split-plot design with four treatment replicates and 3°C, 2.5 kPa O2, and 0.03 or 2.5 kPa CO2 with or without 1 μL L(-1) 1-MCP. Total PA levels were not elevated by the 1-MCP treatment. Examination of the individual PAs revealed that: (i) total putrescine levels tended to be lower with 1-MCP regardless of the CO2 level, and while this was mostly at the expense of free putrescine, large transient increases in soluble conjugated putrescine were also evident; (ii) total spermidine levels tended to be lower with 1-MCP, particularly at 2.5 kPa CO2, and this was mostly at the expense of soluble conjugated spermidine; (iii) total spermine levels at 2.5 kPa CO2 tended to be lower with 1-MCP, and this was mostly at the expense of both soluble and insoluble conjugated spermine; and (iv) total spermidine and spermine levels at 0.03 kPa were relatively unaffected, compared to 2.5 kPa CO2, but transient increases in free spermidine and spermine were evident. These findings might be due to changes in the conversion of putrescine into higher PAs and the interconversion of free and conjugated forms in apple fruit, rather than altered S-adenosylmethionine availability. Regardless of 1-MCP and CO2 treatments, the availability of glutamate showed a transient peak initially, probably due to protein degradation, and this was followed by a steady decline over the remainder of the storage period which coincided with linear accumulation of GABA. This pattern has been attributed to the stimulation of glutamate decarboxylase activity and inhibition of GABA catabolism, rather than a contribution of PAs to GABA production.
1-甲基环丙烯（1-MCP）可延缓苹果（Malus domestica Borkh.）果实在受控气氛（CA）贮藏期间的乙烯介导的成熟。在这里，我们测试了以下假设，即 1-MCP 和 CA 贮藏可提高苹果果实中的多胺（PAs）和 4-氨基丁酸（GABA）的水平。使用“帝国”苹果进行了一项为期 46 周的实验，采用裂区设计，处理重复 4 次，3°C、2.5kPa O2 和 0.03 或 2.5kPa CO2，有无 1μL L(-1) 1-MCP。1-MCP 处理并未提高总多胺水平。对各多胺的检查表明：（i）1-MCP 处理下，无论 CO2 水平如何，腐胺总量往往较低，尽管这主要是由于游离腐胺，但也明显存在可溶性共轭腐胺的短暂大量增加；（ii）1-MCP 处理下，总亚精胺水平往往较低，尤其是在 2.5kPa CO2 下，这主要是由于可溶性共轭亚精胺；（iii）2.5kPa CO2 下，1-MCP 处理下总精胺水平往往较低，这主要是由于可溶性和不溶性共轭精胺；以及（iv）0.03kPa 下的总亚精胺和精胺水平与 2.5kPa CO2 相比相对不受影响，但游离亚精胺和精胺的短暂增加明显。这些发现可能是由于苹果果实中腐胺向更高多胺的转化以及游离和共轭形式的相互转化发生变化，而不是 S-腺苷甲硫氨酸可用性的改变。无论 1-MCP 和 CO2 处理如何，谷氨酸的可用性最初都会出现短暂的峰值，可能是由于蛋白质降解所致，随后在整个贮藏期内持续下降，这与 GABA 的线性积累相吻合。这种模式归因于谷氨酸脱羧酶活性的刺激和 GABA 分解代谢的抑制，而不是 PAs 对 GABA 产生的贡献。
