Bucheli C S, Dry I B, Robinson S P
CSIRO Division of Horticulture, Adelaide, Australia.
Plant Mol Biol. 1996 Sep;31(6):1233-8. doi: 10.1007/BF00040840.
Polyphenol oxidase (PPO) activity in sugarcane (a C4 grass) was highest in the growing point and declined down the stalk. Sugarcane PPO with an apparent molecular mass of 45 kDa was purified to homogeneity from immature stem tissue. Western analysis of sugarcane extracts with a polyclonal antibody raised to this protein suggested it resulted from cleavage of a 60 kDa protein during purification. The antibody was used to screen a sugarcane stem cDNA library. A full-length PPO clone (sugppo 1) was characterised and shown to encode a 67 kDa precursor protein comprising a plastid transit sequence of 8 kDa and a mature PPO protein of 59 kDa. High levels of expression of sugppo 1 were detected in the growing point of the stalk and in the immature tissue immediately below it, but no message was detected in RNA from mature stem or leaf. Comparison with other PPO sequences indicated that sugppo 1 was significantly different to PPO genes in C3 dicotyledonous plants.
多酚氧化酶（PPO）在甘蔗（一种C4禾本科植物）中的活性在生长点最高，沿茎向下递减。从未成熟茎组织中纯化出了表观分子量为45 kDa的甘蔗PPO，并使其达到了均一性。用针对该蛋白制备的多克隆抗体对甘蔗提取物进行的Western分析表明，它是在纯化过程中由一种60 kDa的蛋白裂解产生的。该抗体被用于筛选甘蔗茎cDNA文库。对一个全长PPO克隆（sugppo 1）进行了表征，结果显示它编码一个67 kDa的前体蛋白，该前体蛋白包含一个8 kDa的质体转运序列和一个59 kDa的成熟PPO蛋白。在茎的生长点及其下方紧邻的未成熟组织中检测到了sugppo 1的高表达水平，但在成熟茎或叶的RNA中未检测到相关信息。与其他PPO序列的比较表明，sugppo 1与C3双子叶植物中的PPO基因有显著差异。
