SUMMARY
The colonisation of land by plants is considered a major event in the history of Earth, which ultimately also allowed animals to colonise land. The change from aquatic to terrestrial habitats brought a number of challenges for plants, including light conditions that are different on land compared to aquatic habitats.
Phytochromes are photoreceptors enabling plants to respond to various light conditions.
Independent gene duplication events resulted in small phytochrome gene families in mosses, ferns, and seed plants. This phytochrome diversity is hypothesised to be critical for sensing and adapting to different light conditions, but experimental evidence for this idea is lacking for mosses and ferns.
The model moss species Physcomitrium patens contains seven phytochromes grouped into three clades. Here, we used CRISPR/Cas9 generated single and higher order mutants to investigate the role of different phytochromes in light-regulation of protonema and gametophore growth, protonema branching, and induction of gametophores.
We found both specific and partially overlapping roles for the three clades of moss phytochromes in regulating these responses in red, far-red, or blue light, and we identified a mechanism for sensing simulated canopy shade that is different from the mechanism used by seed plants.
Competing Interest Statement
The authors have declared no competing interest.