PRBP plays a role in plastid ribosomal RNA maturation and chloroplast biogenesis in <Emphasis Type="Italic">Nicotiana benthamiana</Emphasis> |
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Authors: | Yong-Joon Park Hui-Kyung Cho Hyun Ju Jung Chang Sook Ahn Hunseung Kang Hyun-Sook Pai |
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Institution: | (1) Department of Biology, Yonsei University, Seoul, 120-749, Korea;(2) Department of Plant Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 500-757, Korea; |
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Abstract: | In the present study, we investigated protein characteristics and physiological functions of PRBP (plastid RNA-binding protein)
in Nicotiana benthamiana. PRBP fused to green fluorescent protein (GFP) localized to the chloroplasts. Recombinant PRBP proteins bind to single-stranded
RNA in vitro, but not to DNA in a double- or a single-stranded form. Virus-induced gene silencing (VIGS) of PRBP resulted in leaf yellowing in N. benthamiana. At the cellular level, PRBP depletion disrupted chloroplast biogenesis: chloroplast number and size were reduced, and the
thylakoid membrane was poorly developed. In PRBP-silenced leaves, protein levels of plastid-encoded genes were significantly reduced, whereas their mRNA levels were normal
regardless of their promoter types indicating that PRBP deficiency primarily affects translational or post-translational processes.
Depletion of PRBP impaired processing of the plastid-encoded 4.5S ribosomal RNA, resulting in accumulation of the larger precursor
rRNAs in the chloroplasts. In addition, PRBP-deficient chloroplasts contained significantly reduced levels of mature 4.5S
and 5S rRNAs in the polysomal fractions, indicating decreased chloroplast translation. These results suggest that PRBP plays
a role in chloroplast rRNA processing and chloroplast development in higher plants. |
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