Resolving the structure of the ´eyes´ of plants.

All plants constantly adapt to sunlight, regulating their growth, development, and reproduction.

The response is enabled by phytochrome proteins, which detect red and far-red light and regulate gene expression through complex signaling networks. The networks are prime targets for plant engineering by mutations, but atomic scale understanding is lacking.

In particular, the three-dimensional structure of plant phytochromes is not known, and it remains unclear how phytochromes bind to signaling partners.Here, we propose to uncover the first structure of a full-length plant phytochrome to near-atomic resolution, in both resting and photoactive states, and in complex with signaling partner proteins.

We plan to use single-particle cryogenic electron microscopy.

Feasibility is strongly supported by our recent structure of a full-length plant phytochrome at low resolution (Wahlgren, Front. of Plant Science, 2021).

Based on the new structures, we will engineer phytochrome complexes by site-selective mutations and demonstrate the effect in vivo on light-dependent growth of Arabidopsis thaliana.The project may results in a pioneering structural basis for light sensing by phytochromes in plants, explaining with atomic precision how vegetation adapts to light.

Moreover, we will open up for engineering of plants by few-site modifications of phytochrome complexes, opening a new route to increased efficiency and sustainability in agriculture.