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J Exp Bot. 2016 Oct;67(18):5447-5460. Epub 2016 Aug 29.

Essential role of conserved DUF177A protein in plastid 23S rRNA accumulation and plant embryogenesis.

Author information

1
Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32611, USA.
2
Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32611, USA Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA.
3
Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32611, USA Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA drm@ufl.edu.

Abstract

DUF177 proteins are nearly universally conserved in bacteria and plants except the Chlorophyceae algae. Thus far, duf177 mutants in bacteria have not established a function. In contrast, duf177a mutants have embryo lethal phenotypes in maize and Arabidopsis. In maize inbred W22, duf177a mutant embryos arrest at an early transition stage, whereas the block is suppressed in the B73 inbred background, conditioning an albino seedling phenotype. Background-dependent embryo lethal phenotypes are characteristic of maize plastid gene expression mutants. Consistent with the plastid gene expression hypothesis, quantitative real-time PCR revealed a significant reduction of 23S rRNA in an Escherichia coli duf177 knockout. Plastid 23S rRNA contents of duf177a mutant tissues were also markedly reduced compared with the wild-type, whereas plastid 16S, 5S, and 4.5S rRNA contents were less affected, indicating that DUF177 is specifically required for accumulation of prokaryote-type 23S rRNA. An AtDUF177A-green fluorescent protein (GFP) transgene controlled by the native AtDUF177A promoter fully complemented the Arabidopsis atduf177a mutant. Transient expression of AtDUF177A-GFP in Nicotiana benthamiana leaves showed that the protein was localized in chloroplasts. The essential role of DUF177A in chloroplast-ribosome formation is reminiscent of IOJAP, another highly conserved ribosome-associated protein, suggesting that key mechanisms controlling ribosome formation in plastids evolved from non-essential pathways for regulation of the prokaryotic ribosome.

KEYWORDS:

Arabidopsis thaliana ; Zea mays. ; DUF177; background-dependent phenotype; chloroplast ribosome; embryogenesis

PMID:
27574185
PMCID:
PMC5049393
DOI:
10.1093/jxb/erw311
[Indexed for MEDLINE]
Free PMC Article

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