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The rice virescent-2 mutant (v2) is temperature conditional and develops chlorotic, chloroplast-deficient leaves at the restrictive temperature. In the v2 mutant, plastid-encoded proteins involved in photosynthesis and plastid transcriptional regulation were not detectable at any time during chloroplast differentiation. However, the plastid transcripts for these two classes of proteins behaved differently in the mutant, with those for the plastid transcription/translation apparatus accumulating to wild-type levels and those for photosynthetic apparatus being suppressed. Polysome analysis showed that translation of the plastid transcripts encoding the plastid transcription/translation apparatus was blocked at an early stage of chloroplast differentiation. Accumulation of transcripts of nuclear-encoded photosynthetic genes, such as cab and rbcS, was strongly suppressed in the mutant at later stages of chloroplast differentiation, whereas transcripts of genes for the plastid transcription apparatus, such as OsRpoTp and OsSIG2A, accumulated to abnormally high levels at these stages. These results suggest that activation of the plastid translation machinery at an early stage of chloroplast differentiation is important for triggering the transmission of information about plastid developmental state to the nucleus, which in turn is required for the induction of nuclear-encoded chloroplast proteins at later stages of chloroplast differentiation.
Keywords: Keywords: Chloroplast development — Nuclear-encoded plastid RNA polymerase (NEP) — Plastid-encoded plastid RNA polymerase (PEP) — Rice — Translational control — viresent-2.; Abbreviations: CAB, chlorophyll a/b-binding protein; DDT, dithiothreitol; EGTA, ethylene glycol bis(β-aminoethylether)-N,N,N′,N′-tetraacetic acid; EST, expressed sequence tags; LHCPII, chlorophyll a/b binding protein of light harvesting complex II; v2, virescent-2; NEP, nuclear-encoded plastid RNA polymerase; PEP, plastid-encoded plastid RNA polymerase; SB, shoot base; L4, unemerged fourth leaf; L3LS, leaf sheath of the third leaf; L3L, basal half of blade of the third leaf; L3U, upper half of blade of the third leaf.
Journal Article. 8089 words. Illustrated.
Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry
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