PRDA1, a novel chloroplast nucleoid protein, is required for early chloroplast development and is involved in the regulation of plastid gene expression in Arabidopsis.

Chloroplast development requires accurate spatio-temporal expression of plastid genes. The regulation of plastid genes mediated by plastid-encoded RNA polymerase (PEP) is rather complex, and its related mechanism remains largely unclear. Here, we report the identification of a novel protein that is essential for plant development, PEP-Related Development Arrested 1 Knock-out of in Arabidopsis (prda1 mutant) caused a seedling-lethal, albino phenotype and arrested the development of leaf chloroplasts. Localization analysis showed that Pduanyu16501 was specifically targeted to chloroplasts and co-localized with chloroplast nucleoids, revealing that Pduanyu16501 is a chloroplast nucleoid-associated protein. Gene expression analyses revealed that the PEP-dependent plastid transcript levels were greatly reduced in prda1. Pduanyu16501 was co-expressed with most of the PEP-associated proteins. Protein interaction assays showed that Pduanyu16501 clearly interacts with MRL7 and FSD2, both of which have been verified as essential for PEP-related chloroplast development. Reactive oxygen species scavenging through dimethylthiourea markedly alleviated the cotyledon-albino phenotypes of Pduanyu16501 and MRL7 RNA interference seedlings. These results demonstrate that Pduanyu16501 is required for early chloroplast development and involved in the regulation of plastid gene expression.

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