A tRNA gene mapping within the chloroplast rDNA cluster is differentially expressed during the development of Daucus carota

Abstract

In vivo analysis of expression of the chloroplast rDNA cluster during somatic embryogenesis of Daucus carota (D.carota) was performed by Northern-blot analysis with different DNA probes, spanning both the 16S rRNA gene, the 16S-23S rRNA spacer, which contains the two mosaic tRNA genes tRNAlle and tRNAAla, and the region upstream of the 16S rRNA gene, where a tRNAVal maps. We show that expression both of the spacer tRNAs tRNAlle and tRNAAla is not significantly regulated during development whereas the amount of the transcript corresponding to tRNAVal is not detectable during early embryonic stages and progressively accumulates during late phases. Multiple transcription start sites have been identified upstream of the tRNAVal gene by S1 mapping analysis, which are activated late during the embryogenesis. These data indicate that developmental control mechanisms act on plastid gene expression during embryogenesis in carrot. © 1994 Oxford University Press.