Tao R, Uratsu S L, Dandekar A M
Department of Pomology, University of California, Davis 95616, USA.
Plant Cell Physiol. 1995 Apr;36(3):525-32. doi: 10.1093/oxfordjournals.pcp.a078789.
The apple (Malus domestica) cDNA encoding NADP-dependent sorbitol-6-phosphate dehydrogenase (S6PDH) was stably integrated and expressed in transgenic tobacco (Nicotiana tabacum cv. SR1). Expression of the cDNA in either a sense or antisense orientation was accomplished using cauliflower mosaic virus regulatory sequences (CaMV35S). Sorbitol synthesis was confirmed by gas-chromatography-mass-spectroscopy (GC-MS). Sorbitol concentration in the leaves of the transgenic plants expressing the sense orientation varied from 186 to 446 nmol (g fr wt)-1. The concentration positively correlates with S6PDH activity in leaves. Neither sorbitol nor S6PDH activity was detected in the extracts of nontransformed tobacco or transgenic tobacco expressing the antisense orientation. These results provide key genetic evidence that S6PDH expression is sufficient for the synthesis of sorbitol in tobacco, implicating it as a key enzyme in the sorbitol biosynthetic pathway in apple and perhaps other members of the woody Rosaceae.
编码依赖于烟酰胺腺嘌呤二核苷酸磷酸（NADP）的山梨醇-6-磷酸脱氢酶（S6PDH）的苹果（苹果属）cDNA被稳定整合并在转基因烟草（烟草品种SR1）中表达。使用花椰菜花叶病毒调控序列（CaMV35S）以正义或反义方向完成该cDNA的表达。通过气相色谱-质谱联用（GC-MS）确认了山梨醇的合成。表达正义方向的转基因植物叶片中山梨醇浓度在186至446 nmol（鲜重）-1之间变化。该浓度与叶片中的S6PDH活性呈正相关。在未转化烟草或表达反义方向的转基因烟草提取物中均未检测到山梨醇和S6PDH活性。这些结果提供了关键的遗传学证据，表明S6PDH的表达足以在烟草中合成山梨醇，这意味着它是苹果以及可能蔷薇科其他木本植物中山梨醇生物合成途径中的关键酶。
