Engineering RNA binding proteins to control plant mitochondrial respiratory function and fertility

• Applicant: Dr. Elena Lesch
• Subject Area: Plant Physiology ; Plant Genetics and Genomics ; Plant Cell and Developmental Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576009574

Mitochondria are central hubs of energy production in eukaryotes. Having derived from a free-living bacterium, they retain a small genome encoding few genes, primarily involved in oxidative phosphorylation (OXPHOS) and mitochondrial protein biosynthesis. OXPHOS is the key process for ATP synthesis – the cell’s primary energy currency, and takes place in the inner mitochondrial membrane (IMM). It relies on the active generation of a proton gradient across the IMM, driving ATP production via ATP synthase. OXPHOS depends on the coordinated function of five multisubunit protein complexes, assembled from nuclear- and mitochondria-encoded subunits, and two mobile electron carriers. Disruption of any component can severely impair organismal fitness and viability. In plants, mitochondrial genome rearrangements or mutations can cause male sterility by triggering the expression of cytotoxic factors. This phenomenon, known as cytoplasmic male sterility (CMS), is exploited in agriculture to produce high-yielding hybrid crops. While the genetic basis of CMS is relatively well understood, the mechanistic link between mitochondrial dysfunction and the specific collapse of the male gametophyte – while other tissues are largely unaffected – remains unclear. To address this, we propose an innovative approach based on synthetic RNA-binding pentatricopeptide repeat (PPR) proteins, which enables precise post-transcriptional control of organellar gene expression – even of essential genes. By inducing targeted mitochondrial dysfunction, we aim to dissect its physiological consequences, such as energy status and fertility, with high resolution, particularly focusing on male reproductive tissue. This approach will not only help clarify the mechanism of CMS, but also provide a broadly applicable framework to study mitochondrial gene function in a tissue-specific and reversible manner. In current breeding practice, fertility in CMS lines is restored by crossing them with restorer lines encoding fertility restorer (Rf) proteins. However, fertility restoration often involves multiple factors, depends on the specific CMS type, and is mechanistically complex. For many CMS systems, the corresponding Rf genes remain unidentified, which limits their use. We propose to engineer PPR protein-based synthetic Rfs to control CMS gene expression – opening new avenues for controlled fertility and next-generation hybrid breeding.

• DFG Programme: WBP Position