Guanylate cyclase activity of TIR1/AFB auxin receptors in rapid auxin responses

Auxin is a pleiotropic plant hormone with diverse functions, many of which are mediated through transcriptional reprograming. However, some auxin responses occur extremely rapidly, ruling out changes in transcription as a mechanism. In 2022, one of the components of an auxin receptor, F-box protein TIR1/AFB, was discovered to include an adenylate cyclase catalytic domain, suggesting a role for cAMP signaling. However, this finding didn’t explain all of the observed effects, particularly the rapid calcium oscillations induced by auxin. Here, Qi et al. provide evidence for a guanylate cyclase catalytic domain adjacent to the previously identified adenylate cyclase domain. They found that cGMP production is rapidly stimulated by auxin, and is involved in the rapid calcium oscillations and root growth responses. These results demonstrate that cGMP is an important second messenger in the auxin response. (Summary by Mary Williams @PlantTeaching) bioRxiv