How plants manage excess solar energy5 December 2016

Electron microscope image of the alga Chlamydomonasreinhardtii. Credit: © Sylvain Loubéry, UNIGE

Life on earth largely depends on the conversion oflight energy into chemical energy throughphotosynthesis by plants. However, absorption ofexcess sunlight can damage the complexmachinery responsible for this process.Researchers from the University of Geneva(UNIGE), Switzerland, have discovered how Chlamydomonas reinhardtii, a mobile single-cellalga, activates the protection of its photosyntheticmachinery. Their study, published in the journal PNAS, indicates that the receptors (UVR8) thatdetect ultraviolet rays induce the activation of asafety valve that allows dissipation of excessenergy as heat. A second protective role is thusattributed to these receptors, whose ability toinduce the production of an anti-UV 'sunscreen'had already been shown by the Geneva team.

The energy of the sun is converted by plants into chemical energy through photosynthesis in order toproduce sugars to feed themselves. The first stepof this process, which takes place in cellcompartments called chloroplasts, is the capture ofphotons of light by chlorophyll. Although light isessential for plants, sun in excess can damagetheir photosynthetic machinery, thereby affectingtheir growth and productivity. To protectthemselves, plants activate a protection mechanismwhen light is too intense, which involves a series ofproteins capable of converting the surplus of energy into heat to be harmlessly dissipated.

Producing proteins that divert energy

"UV-B ultraviolet light is likely to cause the mostdamage to the photosynthetic machinery, and wewanted to know whether it is involved in activatingprotection mechanisms and, if so, how", say MichelGoldschmidt-Clermont and Roman Ulm, professorsat the Department of Botany and Plant Biology ofthe UNIGE Faculty of Science. This work,conducted in collaboration with researchers fromthe Universities of Grenoble and of California, wascarried out in Chlamydomonas reinhardtii, a single-cell mobile alga used as a model organism.

The team of Roman Ulm had discovered in 2011the existence of a UV-B receptor, called UVR8,whose activation allows plants to protectthemselves against these UV and to develop theirown molecular 'sunscreen". The researchersdemonstrate now that this receptor activates asecond protection mechanism. "When UVR8perceives UV-B rays, it triggers a signal thatinduces, at the level of the cell nucleus, theproduction of proteins that will then be imported intothe chloroplasts. Once integrated into the photosynthetic apparatus, they will help to divert excess energy, which will be dissipated as heatthrough molecular vibrations", explains GuillaumeAllorent, first author of the article.

In terrestrial plants, the perception of UV-B by theUVR8 receptor is also important for the protection

1 / 2

of the photosynthetic machinery, but the underlyingmechanism has not yet been elucidated. "It iscrucial for agricultural productivity and thebiotechnological exploitation of photosyntheticprocesses to better understand the mechanismsleading to photoprotection under sunlight and itsUV-B rays", says Michel Goldschmidt-Clermont. Aproject the Genevan team intends to pursue.

More information: UV-B photoreceptor-mediatedprotection of the photosynthetic machinery inChlamydomonas reinhardtii, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1607695114

Provided by University of GenevaAPA citation: How plants manage excess solar energy (2016, December 5) retrieved 24 May 2022 from https://phys.org/news/2016-12-excess-solar-energy.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, nopart may be reproduced without the written permission. The content is provided for information purposes only.

Powered by TCPDF (www.tcpdf.org)

2 / 2