Phytochrome cytoplasmic signalling in lower plants
Plant Physiology
Final Report Abstract
In this project we investigated the working of phytochrome, a red-light-sensitive receptor molecule used by plants to regulate thousands of genes in their genome. Remarkably, phytochrome in mosses also directs growth towards a light source – yet that cannot possibly happen via gene regulation! We set about finding out how it happens, not because we are especially interested in mosses, but because we want to know how phytochromes work. Earlier, we and others had discovered that certain ferns and algae use "neochrome" photoreceptors to optimize chloroplast position for photosynthesis. Neochromes are remarkable because they comprising two modules; one a phytochrome, the other a phototropin, a receptor that higher plants use to steer growth direction and chloroplast movement from the plasma membrane in response to blue light. In neochromes, the phytochrome module seems to have been joined to the phototropin to take over its functions in the cell. Mosses show phytochrome-steered growth direction – but, unfortunately, like higher plants, they don't have neochromes! Using molecular genetic methods in the moss Physcomitrella, we found the phytochrome principally responsible for steering growth towards the light. Now we wanted to find out how ... The main result of the present project was the remarkable and quite unexpected finding that that phytochrome hitches a ride on phototropin, perhaps kidnapping its signalling system to direct growth towards red light – rather like the situation in neochromes! Although most of this work was focussed on Physcomitrella, we also showed that phytochrome-phototropin binding occurs in higher plants too, suggesting that it might be a general feature of phytochrome action that has up to now gone unnoticed. Subsequently, we found various other proteins that bind the phytochrome and might be associated with the signalling system in the cell. Most recently, to help us investigate that system, we developed CRISPR methods allowing us to inactivate numerous genes simultaneously. In particular, we were able to target various phytochrome genes in Physcomitrella simultaneously, allowing us now to dissect their different physiological functions. In this work we have expanded basic understanding of phytochrome function. What use that knowledge might have, for example in agriculture, remains to be seen.
Publications
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(2013) Phytochrome cytoplasmic signaling. Annual Review of Plant Biology, 64, 377-402
Hughes J
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(2014) Nuclear Phytochrome B regulates leaf flattening through Phytochrome Interacting Factors. Molecular Plant, 7, 1693-1696
Johansson H, Hughes J
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(2016) Holophytochrome-interacting proteins in Physcomitrella: putative actors in phytochrome cytoplasmic signaling. Frontiers in Plant Sci 7, 613
Ermert AL, Mailliet K, Hughes J
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(2019) Analysis of Physcomitrella phytochrome mutants via photo- and polarotropism. Methods in Molecular Biology 2026, 225-236
Ermert AL, Stahl F, Gans T, Hughes J
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(2019) CRISPR/Cas9-mediated knockout of Physcomitrella patens phytochromes. Methods in Molecular Biology 2026, 237-263
Ermert AL, Nogué F, Stahl F, Gans T, Hughes J
