Abstract
BackgroundEven though the roles of pentatricopeptide repeat (PPR) proteins are essential in plant organelles, the function of many chloroplast-targeted PPR proteins remains unknown. Here, we characterized the function of a chloroplast-localized PPR protein (At3g59040), which is classified as the 287th PPR protein among the 450 PPR proteins in Arabidopsis (http://ppr.plantenergy.uwa.edu.au).ResultsThe homozygous ppr287 mutant with the T-DNA inserted into the last exon displayed pale-green and yellowish phenotypes. The microRNA-mediated knockdown mutants were generated to further confirm the developmental defect phenotypes of ppr287 mutants. All mutants had yellowish leaves, shorter roots and height, and less seed yield, indicating that PPR287 is crucial for normal Arabidopsis growth and development. The photosynthetic activity and chlorophyll content of ppr287 mutants were markedly reduced, and the chloroplast structures of the mutants were abnormal. The levels of chloroplast rRNAs were decreased in ppr287 mutants.ConclusionsThese results suggest that PPR287 plays an essential role in chloroplast biogenesis and function, which is crucial for the normal growth and development of Arabidopsis.
Highlights
Even though the roles of pentatricopeptide repeat (PPR) proteins are essential in plant organelles, the function of many chloroplast-targeted PPR proteins remains unknown
We show that PPR287 affects the level of chloroplast rRNAs, which is essential for chloroplast biogenesis and function as well as for the normal growth and development of Arabidopsis
green fluorescent protein (GFP) signals were observed in the chloroplasts of PPR287-GFP expressing transgenic plants (Fig. 1b), whereas GFP signals were detected in the nucleus and cytoplasm of GFP-expressing transgenic plants (Additional file 1), indicating that the nucleus-encoded PPR287 is transported into chloroplasts
Summary
Even though the roles of pentatricopeptide repeat (PPR) proteins are essential in plant organelles, the function of many chloroplast-targeted PPR proteins remains unknown. Chloroplast gene expression is modulated and regulated by posttranscriptional processes, such as mRNA and tRNA splicing, mRNA editing, RNA stability, and translational control, during which many RNAbinding proteins (RBPs) play essential roles [8,9,10,11,12]. The pentatricopeptide repeat (PPR) proteins are among the nucleus-encoded chloroplast RBPs. Notably, PPR proteins are abundant in land plants [15,16,17]. The Arabidopsis genome encodes more than 450 PPR proteins, whereas less than 10 PPR proteins are found in humans [15, 18], suggesting their plant-specific functions. The P-class PPR proteins that harbor only the PPR motifs are involved in intercistronic processing, splicing of group II introns, and RNA stabilization, whereas the PLSclass PPR proteins that contain additional C-terminal domains, such as E, E+, and DYW, are required for C to U RNA editing [17, 19, 20]
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