Drakakaki Georgia, Marcel Sylvain, Arcalis Elsa, Altmann Friedrich, Gonzalez-Melendi Pablo, Fischer Rainer, Christou Paul, Stoger Eva
Institute for Molecular Biotechnology, Biology VII, Aachen University, 52074 Aachen, Germany.
Plant Physiol. 2006 Jun;141(2):578-86. doi: 10.1104/pp.106.076661. Epub 2006 Apr 21.
Recombinant proteins directed to the secretory pathway in plants require a signal peptide for entry into the endoplasmic reticulum. In the absence of further targeting information, such proteins are generally secreted via the default pathway to the apoplast. This has been well documented in protoplasts and leaf tissue, but the trafficking of recombinant proteins in seeds and other storage tissues has rarely been investigated. We used Aspergillus niger phytase as a model glycoprotein to compare the intracellular fate of a recombinant protein in the leaves and seeds of rice (Oryza sativa). Using fluorescence and electron microscopy we showed that the recombinant protein was efficiently secreted from leaf cells as expected. In contrast, within endosperm cells it was retained in endoplasmic reticulum-derived prolamin bodies and protein storage vacuoles. Consistent with our immunolocalization data, the phytase produced in endosperm cells possessed oligomannose and vacuolar-type N-glycans [Man(3)(Xyl)(Fuc)GlcNAc(2)], whereas the phytase produced in leaves contained predominantly secretion-type N-glycans [GlcNAc(2)Man(3)(Xyl)(Fuc)GlcNAc(2)]. The latter could not be detected in preparations of the endosperm-derived phytase. Our results show that the intracellular deposition and modification of a recombinant protein is tissue dependent.
靶向植物分泌途径的重组蛋白进入内质网需要信号肽。在没有进一步靶向信息的情况下，此类蛋白通常通过默认途径分泌到质外体。这在原生质体和叶片组织中已有充分记录，但重组蛋白在种子和其他贮藏组织中的运输很少被研究。我们使用黑曲霉植酸酶作为模型糖蛋白，比较重组蛋白在水稻（Oryza sativa）叶片和种子中的细胞内命运。通过荧光显微镜和电子显微镜，我们发现重组蛋白如预期那样从叶细胞中有效分泌。相反，在内胚乳细胞中，它保留在内质网衍生的醇溶蛋白体和蛋白贮藏液泡中。与我们的免疫定位数据一致，在内胚乳细胞中产生的植酸酶具有高甘露糖型和液泡型N-聚糖[Man(3)(Xyl)(Fuc)GlcNAc(2)]，而在叶片中产生的植酸酶主要含有分泌型N-聚糖[GlcNAc(2)Man(3)(Xyl)(Fuc)GlcNAc(2)]。在内胚乳来源的植酸酶制剂中未检测到后者。我们的结果表明，重组蛋白的细胞内沉积和修饰是组织依赖性的。
