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Intersection of phytochrome signalling and temperature acclimation in Arabidopsis

Reference	BB/D000483/1
Principal Investigator / Supervisor	Professor Garry Whitelam
Co-Investigators / Co-Supervisors	Prof. Keara Franklin
Institution	University of Leicester
Department	Biology
Funding type	Research
Value (£)	237,024
Status	Completed
Type	Research Grant
Start date	01/08/2005
End date	31/08/2008
Duration	37 months

Abstract

Light signals, perceived via the red/ far-red (R/FR) light-absorbing phytochrome family of plant photoreceptors, and ambient temperature are amongst the most important environmental cues regulating plant development. In Arabidopsis, five discrete apophytochrome-encoding genes, PHYA-PHYE have been isolated and sequenced. Despite the importance of phytochromes for plant growth, relatively little is known about how phytochrome signalling interacts with other environmental stimuli to modulate developmental processes. A particularly important role of the phytochromes involves detection of the presence of neighbouring vegetation by sensing changes in the quality of reflected/transmitted light. In many species, these changes in light quality (reduced R:FR ratio) lead to pronounced elongation growth of petioles and stems with concomitant alterations in leaf and root morphology, as well as a marked acceleration of flowering. These responses have been typically studied using plants that have been grown at temperatures in excess of 22C. However, for most Northern European ecotypes of Arabidopsis this would exceed monthly mean spring and summer temperatures. When grown at cooler temperatures (16C), Arabidopsis plants display several developmental differences in their response to low R:FR ratio. In addition, we have found that low R:FR ratio signals in plants grown at 16C lead to increased transcript levels for a sub-set of genes that are normally considered to be cold-induced and that are associated with the acquisition of freezing tolerance. Furthermore, we have evidence that phytochrome action can lead to freezing tolerance at temperatures previously regarded as non-acclimating. We propose a programme of research that will investigate the molecular mechanisms by which phytochrome signals regulate cold-responsive genes. We aim to identify the molecular components involved in cold signalling cascades that are also regulated by phytochrome action.

Summary

Plants perceive light signals using specialised photoreceptors. These include the red (R) and far-red (FR) light/absorbing phytochromes and the blue light-absorbing cryptochromes and phototropins. In the model plant species Arabidopsis, there are five phytochromes which perform both distinct and overlapping roles throughout plant development. Processes under direct phytochrome control include seed germination, elongation growth, leaf size/shape and flowering time. The light-regulated development of plants involves the integration of phytochrome signalling with temperature sensing mechanisms. A key role of the phytochromes involves detection of the presence of neighbouring vegetation by sensing changes in the quality of reflected/transmitted light. Daylight reflected from vegetation is depleted in R and enriched in FR wavelengths. Plants respond to the impending threat of shade (reduced R:FR) by rapidly elongating their stems and leaves. When Arabidopsis plants are grown at temperatures around 16 degrees C, these elongation responses are accompanied by increased expression of several genes that are normally induced by cold (temperatures below 5 degrees C). These genes play a role in the acquisition of freezing tolerance. We propose to investigate exactly how phytochrome signalling interacts with temperature in the regulation of freezing tolerance genes.

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	Plant Science
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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