St-Pierre B, Bertrand C, Camirand A, Cappadocia M, Brisson N
Department of Biochemistry, Université de Montréal, Canada.
Plant Mol Biol. 1996 Mar;30(6):1087-98. doi: 10.1007/BF00019544.
Analysis of the levels of starch phosphorylase mRNA and its product in the various organs of the potato plant indicates that the gene is differentially regulated, leading to a high accumulation of the gene product in tubers. The amount of phosphorylase transcripts synthesized in nuclei isolated from tubers and leaves indicates that the difference in the steady-state levels of phosphorylase mRNA in these organs can be explained by different rates of initiation of transcription. However, while rates of initiation of transcription are similar in tubers and stems, the steady-state level of phosphorylase mRNA is much lower in the stem. Transgenic potato plants expressing the beta-glucuronidase (GUS) gene under the control of 5'-flanking sequences of the phosphorylase gene exhibited high levels of GUS activity in petioles, stems, stolons, tubers and roots, but low levels in leaves. This confirms the results of transcription assays observed for leaves, stems and tubers, and indicates that accumulation of phosphorylase mRNA in stems and tubers is not controlled solely by transcription initiation. Finally, histochemical analysis for GUS activity in transgenic potato plants suggests that transcription of the phosphorylase gene predominantly occurs in starch-containing cells associated to vascular tissues, and suggests a role for starch phosphorylase in the mobilization of starch stored along the translocation pathway.
对马铃薯植株各器官中淀粉磷酸化酶mRNA及其产物水平的分析表明，该基因受到差异调控，导致其基因产物在块茎中大量积累。从块茎和叶片中分离的细胞核中合成的磷酸化酶转录本数量表明，这些器官中磷酸化酶mRNA稳态水平的差异可以通过不同的转录起始速率来解释。然而，虽然块茎和茎中的转录起始速率相似，但茎中磷酸化酶mRNA的稳态水平要低得多。在磷酸化酶基因5'侧翼序列控制下表达β-葡萄糖醛酸酶（GUS）基因的转基因马铃薯植株，在叶柄、茎、匍匐茎、块茎和根中表现出高水平的GUS活性，但在叶片中活性较低。这证实了对叶片、茎和块茎进行转录分析的结果，并表明茎和块茎中磷酸化酶mRNA的积累并非仅由转录起始控制。最后，对转基因马铃薯植株中GUS活性的组织化学分析表明，磷酸化酶基因的转录主要发生在与维管组织相关的含淀粉细胞中，并暗示淀粉磷酸化酶在沿转运途径储存的淀粉动员中起作用。
