Plastid Genes Encoding the Transcription/Translation Apparatus Are Differentially Transcribed Early in Barley (Hordeum vulgare) Chloroplast Development (Evidence for Selective Stabilization of psbA mRNA)

Abstract

Chloroplast genomes encode rRNAs, tRNAs, and proteins involved in transcription, translation, and photosynthesis. l h e expression of 15 plastid genes representing each of these functions was quantitated during chloroplast development in barley (Hordeum vulgare). l h e transcription of all plastid genes increased during the initial phase of chloroplast development and then declined during chloroplast maturation. RNAs corresponding to rpoBrpoC1-rpoC2, which encode subunits of a plastid RNA polymerase, and rpsl6, which encodes a ribosomal protein, reached maximal abundance early in chloroplast development prior to genes encoding subunits of the photosynthetic apparatus (rbcl, afp6, psaA, petB). lranscription of rpoB as well as 16s rRNA, trnfM-tmC, and trnK was high early in chloroplast development and declined 10-fold relative to r b c l transcription during chloroplast maturation. RNA hybridizing to psbA and psbD, genes encoding reaction center proteins of photosystem II, was differentially maintained in mature chloroplasts of illuminated barley. Differential accumulation of psbD mRNA relative to r b c l mRNA was due to light-stimulated transcription of psbD. In contrast, enhanced levels of psbA mRNA in mature chloroplasts were due primarily to selective stabilization of the psbA mRNA. These data document dynamic modulation of plastid gene transcription and mRNA stability during barley chloroplast development.

pTAC2, -6, and -12 Are Components of the Transcriptionally Active Plastid Chromosome That Are Required for Plastid Gene Expression

“…Proper expression of plastid genes is essential for the differentiation of proplastids to chloroplasts (Baumgartner et al, 1993;Mache et al, 1997). Hence, defects in plastid gene expression lead to reduced chlorophyll levels and obviously counteract any adverse effects, such as the assembly of thylakoid structures.…”

Unique Architecture of the Plastid Ribosomal RNA Operon Promoter Recognized by the Multisubunit RNA Polymerase in Tobacco and Other Higher Plants

“…The biosynthesis of plastid rRNA is highly regulated during development at both the transcriptional and post-transcriptional levels. In barley, rates of rrn transcription vary by 50-fold and rates of rRNA stability vary by 35-fold in response to developmental and environmental cues (Baumgartner et al, 1993). Rates of rrn transcription were induced 10-fold in pea and tobacco chloroplasts in response to light (DuBell and Mullet, 1995;Shiina et al, 1998;Chun et al, 2001).…”

Expression of the chloroplast genome: modern concepts and experimental approaches

“…Такая организация способствует дифференциальной экспрессии генов транскрипционного/трансляционного аппарата от-носительно генов, кодирующих фотосинтетические белки (Baumgartner et al, 1993).…”