Department of Genetics, Vrije Universiteit, de Boelelaan 1087, NL-1081, HV Amsterdam, The Netherlands.
Theor Appl Genet. 1986 Nov;73(1):94-101. doi: 10.1007/BF00273725.
To study the control of differential gene expression during plastid biogenesis in Petunia hybrida, we have investigated the in vivo translation and transcription of the rbc L gene, coding for the large subunit of ribulose bisphosphate carboxylase (LSU), and the psa A gene, coding for P700 chlorophyll-a apoprotein (AP700). Differential expression of these plastid-encoded genes was studied in two developmentally different plastid systems, proplastid-like organelles from the green cell suspension AK2401 and mature chloroplasts from green leaves. In vivo translation of rbc L and psa A transcripts was analysed using specific antibodies. Specific transcript levels were analysed using internal fragments of the rbc L and psa A genes. A standardization procedure was used so that a direct correlation could be made between the amount of products and gene copy number. In Petunia hybrida the amount of LSU polypeptides present in both plastid types does not correspond to the amount of specific mRNA for the gene. Although the rbc L transcripts are present in both plastid types, the LSU protein is only present in green leaf plastids and not in cell culture plastids. In vitro translation of isolated rbc L transcripts give similar results, thereby suggesting that differences in the primary structure of the transcripts are responsible for the observed discrepancy. In contrast to this, the amount of AP700 polypeptides does correspond to the amount of the psa A transcripts. Therefore, our results indicate that the expression of chloroplast genes during plastid biogenesis takes place on at least two different levels: expression of the rbc L gene is regulated post-transcriptionally while expression of the psa A gene is regulated at the transcriptional level.
为了研究在矮牵牛质体生物发生过程中差异基因表达的调控，我们研究了编码核酮糖二磷酸羧化酶大亚基（LSU）的 rbcL 基因和编码 P700 叶绿素-a 脱辅基蛋白（AP700）的 psaA 基因的体内翻译和转录。在两个不同发育阶段的质体系统中研究了这些质体编码基因的差异表达：来自绿色细胞悬浮 AK2401 的原质体样细胞器和来自绿叶的成熟叶绿体。使用特异性抗体分析 rbcL 和 psaA 转录物的体内翻译。使用 rbcL 和 psaA 基因的内部片段分析特定的转录物水平。使用标准化程序，使产物的数量与基因拷贝数之间可以直接相关。在矮牵牛中，两种质体类型中存在的 LSU 多肽的量与该基因的特异性 mRNA 的量不对应。尽管 rbcL 转录物存在于两种质体类型中，但 LSU 蛋白仅存在于绿叶质体中，而不存在于细胞培养质体中。分离的 rbcL 转录物的体外翻译也给出了类似的结果，从而表明转录物的一级结构差异是导致观察到的差异的原因。与此相反，AP700 多肽的量与 psaA 转录物的量相对应。因此，我们的结果表明，质体生物发生过程中质体基因的表达至少发生在两个不同的水平上：rbcL 基因的表达受转录后调控，而 psaA 基因的表达受转录水平调控。
