Barkan A, Miles D, Taylor W C
EMBO J. 1986 Jul;5(7):1421-7. doi: 10.1002/j.1460-2075.1986.tb04378.x.
To assess possible roles of nuclear genes in chloroplast biogenesis, five photosynthetic mutants of maize with nuclear lesions were characterized with respect to their chloroplast proteins and chloroplast RNAs. Each mutant is deficient in a characteristic set of polypeptides. The high sensitivity and resolution of immunoblot analysis revealed that in no case are polypeptides completely missing. Mutants deficient in the cytochrome f/b6 or photosystem I complex show a coordinate reduction of all of the core subunits of these complexes such that the correct stoichiometries are maintained. RNA transcripts encoding most of the affected plastid-encoded proteins were analyzed on Northern blots. In general, chloroplast RNAs in mutant seedlings were not altered in size or abundance, even when the corresponding protein was barely detectable. Therefore, in most cases the nuclear lesions act within the chloroplast at a post-transcriptional level to prevent expression of chloroplast-encoded polypeptides. One mutant, hcf-38, does show striking alterations in the abundance and size of many chloroplast transcripts. The hcf-38 locus might therefore encode a product that functions in chloroplast transcription or RNA processing.
为了评估核基因在叶绿体生物发生中的可能作用，对五个具有核损伤的玉米光合突变体的叶绿体蛋白和叶绿体RNA进行了表征。每个突变体都缺乏一组特定的多肽。免疫印迹分析的高灵敏度和分辨率表明，在任何情况下多肽都不会完全缺失。缺乏细胞色素f/b6或光系统I复合物的突变体显示这些复合物的所有核心亚基都协同减少，从而维持了正确的化学计量。在Northern印迹上分析了编码大多数受影响的质体编码蛋白的RNA转录本。一般来说，即使相应的蛋白质几乎检测不到，突变体幼苗中的叶绿体RNA在大小或丰度上也没有改变。因此，在大多数情况下，核损伤在叶绿体中在转录后水平起作用，以阻止质体编码多肽的表达。一个突变体hcf-38确实在许多叶绿体转录本的丰度和大小上表现出显著变化。因此，hcf-38基因座可能编码一种在叶绿体转录或RNA加工中起作用的产物。
