Department of Botany, Faculty of Sciences, Palacky University, Olomouc, 783 71, Czech Republic.
Department of Biochemistry, Faculty of Sciences, Palacky University, Olomouc, 783 71, Czech Republic.
New Phytol. 2022 Sep;235(5):1807-1821. doi: 10.1111/nph.18256. Epub 2022 Jun 10.
Seed coats serve as protective tissue to the enclosed embryo. As well as mechanical there are also chemical defence functions. During domestication, the property of the seed coat was altered including the removal of the seed dormancy. We used a range of genetic, transcriptomic, proteomic and metabolomic approaches to determine the function of the pea seed polyphenol oxidase (PPO) gene. Sequencing analysis revealed one nucleotide insertion or deletion in the PPO gene, with the functional PPO allele found in all wild pea samples, while most cultivated peas have one of the three nonfunctional ppo alleles. PPO functionality cosegregates with hilum pigmentation. PPO gene and protein expression, as well as enzymatic activity, was downregulated in the seed coats of cultivated peas. The functionality of the PPO gene relates to the oxidation and polymerisation of gallocatechin in the seed coat. Additionally, imaging mass spectrometry supports the hypothesis that hilum pigmentation is conditioned by the presence of both phenolic precursors and sufficient PPO activity. Taken together these results indicate that the nonfunctional polyphenol oxidase gene has been selected during pea domestication, possibly due to better seed palatability or seed coat visual appearance.
种皮是包裹胚胎的保护组织。除了具有机械保护作用外，还具有化学防御功能。在驯化过程中，种皮的特性发生了改变，包括去除种子休眠。我们使用一系列遗传、转录组学、蛋白质组学和代谢组学方法来确定豌豆多酚氧化酶（PPO）基因的功能。测序分析显示 PPO 基因中存在一个核苷酸插入或缺失，所有野生豌豆样本中都发现了具有功能的 PPO 等位基因，而大多数栽培豌豆都有三个无功能的 ppo 等位基因之一。PPO 功能与种脐色素沉着共分离。在栽培豌豆的种皮中，PPO 基因和蛋白质表达以及酶活性均下调。PPO 基因的功能与种皮中没食子儿茶素的氧化和聚合有关。此外，成像质谱支持这样的假设，即种脐色素沉着受酚类前体和足够的 PPO 活性的存在所决定。综上所述，这些结果表明，在豌豆驯化过程中选择了无功能的多酚氧化酶基因，这可能是由于种子的口感更好或种皮的外观更好。
