Zhang Y, Roberts D M
Department of Biochemistry, University of Tennessee, Knoxville 37996, USA.
Mol Biol Cell. 1995 Jan;6(1):109-17. doi: 10.1091/mbc.6.1.109.
Nodulin 26 is an integral membrane protein of the symbiosome membrane of nitrogen-fixing soybean nodules. We expressed a nodulin 26 cDNA in transgenic tobacco (TN26 tobacco) under the control of the cauliflower mosaic virus 35S promoter to study subcellular targeting and the physiological effect(s) of its expression. Based on Northern and Western blots, the expression of nodulin 26 mRNA and protein in transgenic plants is high in apical shoot sections, flowers, and stems, low in mature leaves, and absent in roots. Western blot analysis revealed high levels of transgenic nodulin 26 protein in tonoplast membranes. In contrast, nodulin 26 protein was not found in isolated plasma membranes, the soluble fraction, nor in chloroplast and mitochondria-enriched membrane fractions. About 50-60% of the flowers and pods from TN26 tobacco plants abscised prematurely. Seed capsule size and seed fill per capsule from the remainder of surviving flowers were about 50% of that of control plants. Pollen viability was found to be normal, but flowers from TN26 tobacco plants showed shorter anther filaments compared with control plants. Normal seed production and capsule size was restored by manually crossing the stigmas from TN26 plants with isolated pollen from either transgenic or control plants. Thus, the aberrant filament growth could have resulted in the reproductive defects associated with the plants.
结节蛋白26是固氮大豆根瘤共生体膜中的一种整合膜蛋白。我们在花椰菜花叶病毒35S启动子的控制下，在转基因烟草（TN26烟草）中表达了结节蛋白26 cDNA，以研究其亚细胞定位及其表达的生理效应。基于Northern和Western印迹分析，结节蛋白26 mRNA和蛋白在转基因植物的顶端茎段、花和茎中表达量高，在成熟叶中表达量低，在根中不表达。Western印迹分析显示，液泡膜中有高水平的转基因结节蛋白26。相反，在分离的质膜、可溶部分以及富含叶绿体和线粒体的膜部分中未发现结节蛋白26。TN26烟草植株约50 - 60%的花和荚果过早脱落。存活花其余部分的种荚大小和每个种荚的种子充实度约为对照植株的50%。发现花粉活力正常，但TN26烟草植株的花与对照植株相比，花药花丝较短。通过将TN26植株的柱头与来自转基因或对照植株的分离花粉进行人工杂交，恢复了正常的种子产量和种荚大小。因此，异常的花丝生长可能导致了与这些植株相关的生殖缺陷。
