Biosciences Research Laboratory, Agricultural Research Service, US Department of Agriculture, 1605 Albrecht Boulevard, Fargo, North Dakota 58102-2765, USA.
J Agric Food Chem. 2010 Oct 13;58(19):10597-605. doi: 10.1021/jf102625a.
Incubation of dormant wild oat (Avena fatua L., isoline M73) caryopses for 1-3 days with Fusarium avenaceum seed-decay isolate F.a.1 induced activity of the plant defense enzyme polyphenol oxidase (PPO). Both extracts and leachates obtained from F.a.1-treated caryopses had decreased abundance of an ∼57 kDa antigenic PPO and increased abundance of antigenic PPOs ranging from ∼52 to 14 kDa, as compared to extracts and leachates from untreated caryopsis. Leachates from caryopsis incubated for 2 days with F.a.1 also had 5.1- and 7.5-fold more total PPO activity/g fwt and specific activity, respectively. Fractionation of leachate proteins by ion-exchange chromatography associated the majority of PPO activity with an ∼36 kDa protein from untreated caryopses and ∼36, 25, and 24 kDa proteins from F.a.1-treated caryopses. Predicted peptide sequences obtained from high-performance liquid chromatography-tandem mass spectrometry analyses indicated that the ∼57 and 36 kDa wild oat proteins had a strong similarity to wheat PPO. However, the 25 and 24 kDa proteins were most similar to a Chitinase and oxalate oxidase, respectively. Our results indicate that F.a.1-induced activation of latent PPO in wild oat caryopsis likely involves a cleavage mechanism allowing activated PPOs to be readily mobilized into their surrounding environment.
将休眠野生燕麦（Avena fatua L.，M73 系）颖果用镰刀菌（Fusarium avenaceum）种子腐烂分离物 F.a.1 孵育 1-3 天，诱导植物防御酶多酚氧化酶（PPO）的活性。与未处理的颖果提取物和浸出液相比，来自 F.a.1 处理的颖果的提取物和浸出液中，约 57 kDa 的抗原性 PPO 丰度降低，而约 52-14 kDa 的抗原性 PPO 丰度增加。与未处理的颖果相比，用 F.a.1 孵育 2 天的颖果的浸出液的总 PPO 活性/g fwt 和比活性分别增加了 5.1 倍和 7.5 倍。用离子交换色谱法对浸出液蛋白进行分级，发现大部分 PPO 活性与未经处理的颖果中的约 36 kDa 蛋白以及经 F.a.1 处理的颖果中的约 36、25 和 24 kDa 蛋白相关联。从高效液相色谱-串联质谱分析获得的预测肽序列表明，约 57 和 36 kDa 的野生燕麦蛋白与小麦 PPO 具有很强的相似性。然而，25 和 24 kDa 蛋白与几丁质酶和草酸盐氧化酶最相似。我们的研究结果表明，F.a.1 诱导的野生燕麦颖果中潜伏 PPO 的激活可能涉及一种裂解机制，允许激活的 PPO 很容易转移到其周围环境中。
