Commonwealth Scientific and Industrial Research Organization Division of Horticulture, GPO Box 350, Adelaide, South Australia 5001 Australia.
Plant Physiol. 1992 Aug;99(4):1619-25. doi: 10.1104/pp.99.4.1619.
Bruce's Sport is a mutant grapevine (Vitis vinifera L.) with green and white variegated fruit derived from the Sultana variety. The white regions of tissue have decreased polyphenol oxidase (PPO) activity resulting in a reduced capacity for browning. Active PPO from Sultana grapes was purified and had an apparent molecular weight of 40,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Western blots indicated that mature Sultana grapes contained a single 40-kilodalton PPO, and young Sultana berries also had small quantities of a 60-kilodalton protein. Bruce's Sport grapes had much less of the 40-kilodalton PPO and greater amounts of the 60-kilodalton band. Protease digestion of Bruce's Sport extracts decreased the proportion of the 60-kilodalton protein and increased the 40-kilodalton band. A cDNA clone of grape PPO was used to probe a northern blot of Sultana and Bruce's Sport RNA and hybridized to a 2.2-kilobase transcript in both grapevines. The level of PPO mRNA was high in the early stages of berry development but then declined. The results suggest that in grapevine the active 40-kilodalton form of PPO is synthesized as a precursor protein of at least 60 kilodaltons, and normal processing is interrupted in Bruce's Sport resulting in the accumulation of the 60-kilodalton inactive preform of PPO.
布鲁斯运动型葡萄（Vitis vinifera L.）是一种突变葡萄，其果实呈绿色和白色相间的斑驳状，源自苏丹娜品种。组织的白色区域多酚氧化酶（PPO）活性降低，导致褐变能力降低。从苏丹娜葡萄中纯化出的活性 PPO 在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳中具有约 40,000 的表观分子量。Western blot 分析表明，成熟的苏丹娜葡萄含有单一的 40kDa PPO，而年轻的苏丹娜浆果也含有少量的 60kDa 蛋白。布鲁斯运动型葡萄的 40kDa PPO 含量较少，而 60kDa 带的含量较多。Bruce's Sport 提取物的蛋白酶消化降低了 60kDa 蛋白的比例，增加了 40kDa 带的比例。葡萄 PPO 的 cDNA 克隆被用于探测苏丹娜和 Bruce's Sport RNA 的 Northern blot，并与两种葡萄中的 2.2kb 转录物杂交。在浆果发育的早期阶段，PPO 的 mRNA 水平较高，但随后下降。结果表明，在葡萄中，活性 40kDa PPO 形式作为至少 60kDa 的前体蛋白合成，而在 Bruce's Sport 中，正常加工被中断，导致 60kDa 无活性前体 PPO 的积累。
