Origin and evolution of gibberellin signaling in plants

Title: Origin and evolution of gibberellin signaling in plants

Speaker: Miguel Blásquez

Affiliation: Instituto de Biología Molecular y Celular de Plantas (CSIC-U Politècnica de València)

Abstract:

Gibberellins modulate multiple aspects of plant behavior. The molecular mechanism by which these hormones are perceived and how this information is translated into transcriptional changes has been elucidated in vascular plants: gibberellins are perceived by the nuclear receptor GID1, which then interacts with the DELLA nuclear proteins and promote their degradation, resulting in the modification of the activity of transcription factors with which DELLAs interact physically. However, several important questions are still pending: how does a single molecule perform such a vast array of functions along plant development? What property do gibberellins add to plant behavior? A closer look at gibberellin action from an evolutionary perspective can help answer these questions. We have seen that DELLA proteins are conserved in all land plants, and predate the emergence of a full gibberellin metabolic pathway and the GID1 receptor in the ancestor of vascular plants. We propose that the two most relevant characteristics of DELLA proteins were already present in the ancestral land-plant DELLA 450 million years ago: (i) the capacity to interact with dozens of transcription factors; and (ii) the role in the coordination between growth and stress responses in plants. However, the precise way in which DELLAs exert this role in the different plant lineages is very diverse, and depends on the evolution of DELLAs' partners rather than changes in DELLAs themselves.
Finally, we propose that the origin of gibberellin signaling is linked to the recruitment by GID1 of the N-terminal domain in DELLA, which already acted as a transcriptional coactivator domain in the ancestral DELLA proteins.