DNA-binding proteins in plant mitochondria: Implications for transcription

• Major nucleoid proteins in plant mitochondria bind single-stranded DNA (ssDNA).
• Most of them are plant-specific and have roles in homologous recombination.
• Key mitochondrial transcription factors of animals and fungi are absent in plants.
• We propose that ssDNA-binding proteins may facilitate transcription initiation.

The structural complexity of plant mitochondrial genomes correlates with the variety of single-strand DNA-binding proteins found in plant mitochondria. Most of these are plant-specific and have roles in homologous recombination and genome maintenance. Mitochondrial nucleoids thus differ fundamentally between plants and yeast or animals, where the principal nucleoid protein is a DNA-packaging protein that binds double-stranded DNA. Major transcriptional cofactors identified in mitochondria of non-plant species are also seemingly absent from plants. This article reviews current knowledge on plant mitochondrial DNA-binding proteins and discusses that those may affect the accessibility and conformation of transcription start sites, thus functioning as transcriptional modulators without being dedicated transcription factors.