Comparative mutant analyses reveal a novel mechanism of ARF regulation in land plants

The plant hormone auxin regulates a wide variety of transcriptional responses depending on the cell type, environment, and species. How this diversity is achieved may be related to the specific complement of auxin signalling components in each cell. The levels of activators (class-A AUXIN RESPONSE FACTORS) and repressors (class-B ARFs) are particularly important. Tight regulation of ARF protein levels is likely key in determining this balance. Through comparative analysis of novel, dominant mutants in maize and the moss Physcomitrium patens, we have discovered a ~500-million-year-old (myo) mechanism of class-B ARF protein level regulation mediated by proteasome degradation, important in determining cell fate decisions across land plants. Thus, our results add a key piece to the puzzle of how auxin regulates plant development. Overall design: A segregating population of heterozygous dominant Truffula (Trf) and homozygous normal (N) siblings (in W22 backcross background) were grown under greenhouse conditions until 3-weeks old. Shoot apices were harvested and snap frozen in 3 replicate pools (10 individuals per pool), for Trf and N. Total RNA was extracted and sent for sequencing. Read data was quality checked, and used to carry out differential gene expression analysis between Trf and N siblings to identify trasncriptional changes associated with the vegetative Trf phenotypes.