Molecular Biology of Plant Mitochondria

摘要

Mitochondrial genomes of higher plants are more than ten times as large as mitochondrial DNAs in animals. The size difference is explained by additional genes, by internal duplications, and by integrated nuclear and chloroplast sequences. The approximately 100 protein-coding genes in plant mitochondria are transcribed from scattered promoters with unique structures. After transcription, the primary information of mRNA and tRNA precursors is altered by RNA editing, which changes up to 15% of the codon identities. RNA editing is observed in mitochondria of almost all land plants, but has not been found in algae, suggesting that this process became established during the evolutionary transition to land plants. Maturation of mitochondrial RNAs further involves splicing of intervening sequences in cis- and trans-splicing configurations. Excision of some of these introns appears to require RNA editing in the intron sequences. Nonlethal mutations in mitochondrial genes invariably affect pollen maturation and lead to male sterile plants.