Characterisation of a new clade within the mitochondrial transcription termination factor (mTERF) family implicated in fertility restoration in plants.

Most restorer genes in crops encode RNA-binding pentatricopeptide repeat (PPR) proteins. Plants have hundreds of PPR proteins but only a few act as Restorers-of-fertility and these define a clade referred to as ‘Restorer‑of‑fertility‑like’ PPRs (RFL-PPRs). Our research concerns the molecular characterisation of plant RFL genes and their application to hybrid crop breeding.

Recently, several candidates for restorer genes have been found to encode members of the mitochondrial transcription termination factor (mTERF) family in ryeand barley. No sequence similarity between mTERF and PPR proteins exists, however, like PPRs, mTERFs function in RNA-associated processes and can directly bind to RNA. However, mTERFs remain a largely understudied group of organellar sequence-specific RNA-binding proteins in plants.

Our studies have shown that a group of mTERF genes share several genomic features with the RFL-PPR clade. We demonstrated that, as for RFL-PPRs, one clade of mTERF genes is highly expanded in plants, especially cerealsand that they are organised into clusters adjacent to or intermixed with RFL-PPR clusters in the genome. Our analyses revealed that the location of RFL-mTERF clusters overlaps with mapped Rf loci in wheat and rye. Based on these discoveries we named this clade RFL-mTERFs.

Our identification of clustered mTERF sequences that share genome locations and patterns of evolution with RFL-PPRs together with the demonstrated binding of mTERF proteins to organellar RNA are strong indicators mTERFs play a major and hitherto unappreciated role in fertility restoration. The goal of this project is to characterise the newly discovered RFL-mTERF clade and understand its contribution to fertility restoration in plants.

This project is funded by the ARC Future Fellowship (Australian Research Council) and the Thomas Davis Research Grant for Marine, Soil and Plant Biology (Australian Academy of Sciences)