Liso Rosalia, De Tullio Mario C, Ciraci Samantha, Balestrini Raffaella, La Rocca Nicoletta, Bruno Leonardo, Chiappetta Adriana, Bitonti Maria Beatrice, Bonfante Paola, Arrigoni Oreste
Dipartimento di Biologia e Patologia Vegetale, Università di Bari, Via E. Orabona 4, I-70125 Bari, Italia.
J Exp Bot. 2004 Dec;55(408):2589-97. doi: 10.1093/jxb/erh262. Epub 2004 Nov 1.
To understand the function of ascorbic acid (ASC) in root development, the distribution of ASC, ASC oxidase, and glutathione (GSH) were investigated in cells and tissues of the root apex of Cucubita maxima. ASC was regularly distributed in the cytosol of almost all root cells, with the exception of quiescent centre (QC) cells. ASC also occurred at the surface of the nuclear membrane and correspondingly in the nucleoli. No ASC could be observed in vacuoles. ASC oxidase was detected by immunolocalization mainly in cell walls and vacuoles. This enzyme was particularly abundant in the QC and in differentiating vascular tissues and was absent in lateral root primordia. Administration of the ASC precursor L-galactono-gamma-lactone markedly increased ASC content in all root cells, including the QC. Root treatment with the ASC oxidized product, dehydroascorbic acid (DHA), also increased ASC content, but caused ASC accumulation only in peripheral tissues, where DHA was apparently reduced at the expense of GSH. The different pattern of distribution of ASC in different tissues and cell compartments reflects its possible role in cell metabolism and root morphogenesis.
为了解抗坏血酸（ASC）在根系发育中的功能，对南瓜根尖细胞和组织中的ASC、ASC氧化酶和谷胱甘肽（GSH）分布进行了研究。除静止中心（QC）细胞外，ASC在几乎所有根细胞的细胞质中呈规则分布。ASC也出现在核膜表面并相应地出现在核仁中。在液泡中未观察到ASC。通过免疫定位检测到ASC氧化酶主要存在于细胞壁和液泡中。这种酶在QC和分化的维管组织中特别丰富，而在侧根原基中不存在。施用ASC前体L-半乳糖-γ-内酯可显著增加包括QC在内的所有根细胞中的ASC含量。用ASC氧化产物脱氢抗坏血酸（DHA）处理根系也增加了ASC含量，但仅在外围组织中导致ASC积累，在那里DHA显然以GSH为代价被还原。ASC在不同组织和细胞区室中的不同分布模式反映了其在细胞代谢和根系形态发生中的可能作用。
