Adapting to gravity
We are not conscious about how something so simple as gravity influences our lives. How we look, how we move and how we interact with the world around us. And gravity influences plants just as much. You can clearly see this when you compare water- and land-plants. The first ones feel the influence of gravity less.
That is why plants underwent lots of changes when they emerged onto land 500 million years ago. They not only changed in how they looked like, but their physiology and growth changed as well. Now Japanese researchers show in an article “First contact with greater gravity: Moss plants adapted via enhanced photosynthesis mediated by AP2/ERF transcription factors” that one of those adaptations likely was an increase in photosynthetic activity.
Going back to the situation 500 million years ago is impossible. Therefore, the researchers chose to investigate what happens when they grew the model moss Physcomitrium patens at increased gravity.
Qua appearance mosses growing at ten times the normal gravity,10g, grew less high. Also, in terms of photosynthetic activity there were some changes. There was for example, an increase in CO2 exchange, the leaves had larger chloroplasts and there were more leaves in general.
Feeling gravity
The next question was of course which genes are involved in all this. Therefore, the researchers studied the genes that were more active when the mosses grew at 10g. Nine gene-regulating genes stood out. Eight of those belonged to the same gene family, of which it is known they play a role in how plants deal with stress. But those eight were only present in mosses.
Intrigued the researchers proceeded. One of those eight, later called ISSUNBOSHI1, showed the highest activity at increased gravity. To find out more about what this gene does, the researchers studied mosses in which this gene was always on or always off. Was ISSUNBOSHI1 always on, then moss plants growing at normal gravity, 1g, showed similarity with mosses growing at 10g gravity.
But when ISSUNBOSHI1 was always off, then moss plants adapted less when they were grown at 10g gravity. But also, at 1g gravity had those plants lower photosynthetic activity and smaller chloroplasts.
ISSUNBOSHI1 therefore helps moss plants with feeling an increased gravity. But why ISSUNBOSHI1 and similar genes disappeared in most other land plants, that is unclear.
Literature
Yuko T. Hanba et al., First contact with greater gravity: Moss plants adapted via enhanced photosynthesis mediated by AP2/ERF transcription factors. Sci. Adv.11,eado8664(2025). https://www.science.org/doi/10.1126/sciadv.ado8664
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