Fusion proteins derived from transcription activator-like effectors (TALEs) have
recently emerged as genome editing tools for mitochondria. TALE nucleases
(TALENs) have been applied to delete chimeric reading frames and duplicated
(redundant) genes, but produced complex genomic rearrangements, due to the
absence from mitochondria of a pathway for non-homologous end-joining. Here
we report the targeted deletion of a conserved mitochondrial gene, nad9, encoding
a subunit of respiratory complex I. By generating a large number of TALENmediated mitochondrial deletion lines, we isolated, in addition to mutants with
rearranged genomes, homochondriomic mutants harboring a clean nad9 deletion.
Characterization of the nad9 knock-out plants revealed impaired complex I
biogenesis, male sterility, and defects in leaf and flower development. We show
that these defects can be restored by expressing a functional Nad9 protein from the
nuclear genome, thus creating a synthetic cytoplasmic male sterility (CMS) system.
Together, our data (i) demonstrate the feasibility of using genome editing to study
mitochondrial gene functions by reverse genetics, (ii) highlight the role of complex
I in plant development, and (iii) provide proof-of-concept for the construction of
synthetic CMS systems for hybrid breeding by genome editing. Less...