School of Biological Sciences
Royal Holloway University of London
Egham, Surrey, TW20 0EX
United Kingdom

Tel: 01784-414698
Fax: 01784-414224
E-mail: paul.devlin@rhul.ac.uk

The circadian clock controls a wide range of processes in all organisms studied so far, synchronising their physiology and metabolism with the daily light / dark cycle. An endogenous rhythm maintains an approximate 24 hour cycle ensuring an anticipation of diurnal fluctuations and allowing the organism to take maximum advantage of its environment. For example, sensitivity to environmental cues often shows circadian regulation (Devlin, 2005) while annual processes such as photoperiodic regulation of flowering time are also regulated by the clock (Devlin and Kay, 2000a; Devlin, 2006). An understanding of the mechanism of the circadian clock therefore has advantages for a wide range of fields of biological study.

Daily entrainment by light allows the clock to keep the correct time (Devlin, 2002; Devlin, 2004) meaning that light input to the clock plays a role that is equally important as that played by the oscillator mechanism itself. My earlier work demonstrated discrete roles for individual phytochrome and cryptochrome photoreceptors in entrainment of the clock (Somers et al., 1998; Devlin and Kay 1999; Devlin and Kay 2000b; Devlin and Kay 2001).

Recently, work in my lab has demonstrated that FHY3, a component previously identified as being involved in phytochrome A signalling, is essential for regulating red light signals responsible for resetting the clock during the early part of day (Allen et al., 2006). The role for FHY3 is distinct from that played in phyA signalling is distinct from its role in light input to the clock where it acts downstream of multiple phytochromes. This is a feature that FHY3 shows in common with a number of recently discovered components that play distinct roles in photomorphogenesis and in clock regulation.

We are now seeking to determine the mechanism of action of FHY3. Recent findings by the lab of Haiyang Wang indicate that FHY3 acts as a transcription factor binding to a CACGCGC FHY3 binding site (FBS) sequence in the promoters of key components in the phyA signalling pathway. We have identified the FBS in the promoter region of clock components, CCA1 and ELF4. The central clock component, CCA1, shows strong induction of by red light, essentially resetting the clock to a new phase while ELF4 has been shown to be essential for this meaning that both are key to red light input to the clock. We are aiming to identify additional co-acting factors implicated in this process which should allow us to construct a detailed model of red light input into the circadian clock. (Funded by BBSRC grant: BB/F02116X/1, 2008-2011).

A second aspect of my work involves analysis of the shade avoidance syndrome. Many plants adapted to growth in open canopies show a dramatic increase in elongation growth in response to competition for light with neighbouring plants. The phytochrome photoreceptors detect red-depleted light (low red:far-red ratio light) reflected from neighbouring vegetation which induces this shade avoidance response. The shade avoidance syndrome is a good example of an environmental response showing circadian regulation of sensitivity but is perhaps more important in its own right in that it has tremendous negative impact upon agricultural yield if resources are reallocated to elongation growth.

My earlier work identified the specific phytochromes involved in regulating distinct aspects of shade avoidance (Devlin et al., 1996; Devlin et al., 1997a; Devlin et al., 1998; Devlin et al., 1999). More recently I have identified genes differentially expressed in response to shade, under the control of specific phytochromes (Devlin et al., 2003). This was followed by an analysis of the primary targets of shade regulation (Roig-Villanova et al., 2006).

We are currently characterising a number of novel dracula mutants identified in a luciferase reporter screen as showing no avoidance of shade. Other aspects of my work in phytochrome signalling have involved demonstration of direct interaction between phytochrome B and the blue light photoreceptor cryptochrome 2 (Más et al., 2000), and characterisation of the Arabidopsis GATA family transcription factors (Manfield et al., 2007); the latter project using with microarray analysis to identify targets and roles of these factors in light and circadian responses (previously funded by BBSRC grant: 24/G18363 2003-2006).

High R:FR	Low R:FR		High    Low	High    Low
Figure 2. Left: Wild type Arabidopsis grown at high and low red:far red ratio (R:FR). Low R:FR simulates shading by neighbouring vegetation and results in an increase in elongation growth and an acceleration of flowering. Right: dracula (no avoidance of shade) and icarus (extreme avoidance of shade) mutants identified based upon aberrant luciferase reporter activity following shade treatment.

Arabidopsis is the model organism of choice in the plant molecular sciences. However, despite the contemporary superabundance of tools and knowledge concerning the molecular aspects of the biology of this plant, much less has been learned of its ecology.

The objective of this project is to take advantage of the properties that make Arabidopsis desirable as a model organism in a quest to learn more about plant community ecology. An important driver of evolution in ecosystems is competition and there exist many avenues through which this can be investigated, as the plant interacts with a wide variety of organisms in its environment. For the purposes of this research three different responses to competition have been identified as key research areas. Firstly, we are investigating the role of the circadian clock in competition with other plants in artificial competition experiments. Secondly, we are investigating previously uncharacterised phytochrome regulated adaptive light seeking mechanisms giving a competitive advantage as part of the shade avoidance response. And thirdly, in conjunction with Dr Ken Bruce at KCL and Prof. Alan Gange at RHUL, we are investigating the rhizospheric ecology with a view to gaining a better understanding of the ecophysiological and successional factors that drive bacterial community assembly in the plant’s roots. With this research it is hoped that Arabidopsis can be realized as a model in the ecological as well as the molecular sciences.

Devlin P.F., Christie J.M., Terry M.J., (2007) Many hands make light work. J Exp Bot. 58:3071-3077

Manfield, I.W., Jen, C-H., Devlin, P.F., Westhead, D.R., Gilmartin, P.M., (2007) Comprehensive light, clock-regulation and tissue-specific expression analysis suggests redundancy and expression divergence for Arabidopsis GATA gene family members. Plant Physiology 143, 941-958

Devlin, P.F. (2006) Photocontrol of Flowering. In Light and Plant Development. G.C. Whitelam and K.J. Halliday eds. (Oxford: Blackwells), pp 183-210

Allen, T., Koustenis, A., Theodorou, G., Somers, D.E., Kay, S.A., Whitelam, G.C. and Devlin, P.F. (2006) FHY3 specifically gates phytochrome signaling to the circadian clock. Plant Cell 18, 2506-2516

Roig-Villanova, I., Bou, J., Sorin, C., Devlin, P.F. and Martínez-García, J.F. (2006) Identification of primary target genes of phytochrome signaling: early transcriptional control during shade avoidance responses in Arabidopsis. Plant Physiology 141, 85-96

Devlin, P.F. (2005) Circadian Regulation of Photomorphogenesis. In Photomorphogenesis in Plants and Bacteria 3rd Edition. E. Schafer and F. Nagy, eds. (Dordrecht: Springer), pp. 567-604

Devlin, P.F. (2004) Photoreceptors resetting the circadian clock. In Photoreceptors. A. Batschauer, Copy ed., ESP Comprehensive Series in Photosciences. D-P. Häder, G. Jori, Series eds. (Cambridge: RSC), pp 343-368

Devlin PF, Yanovsky MJ, Kay SA (2003) A genomic analysis of the shade avoidance response in Arabidopsis thaliana. Plant Physiology 133, 1617-1629 [Full text 389k]

Devlin, P.F. (2003).Photoreceptors resetting the circadian clock. In Photoreceptors. A. Batschauer, (copy ed.). ESP Comprehensive Series in Photosciences. D-P. Häder, G. Jori (Series eds). Elsevier Science Ltd. Amsterdam. pp343-368

Devlin, P.F. (2002). Signs of the time - Environmental input to the circadian clock. J. Exp. Bot. 53, 1535-1550 [Full text 400k]

Devlin, P.F. and Kay, S.A. (2001). Circadian Photoperception. Annual Review of Physiology 63, 677-694 [Full text 5,166k]

Mas, P., Devlin, P.F., Panda, S. and Kay, S.A. (2000). Functional Interaction of Phytochrome B and Cryptochrome 2. Nature 408, 207-211 [Full text 474k]

Devlin, P.F. and Kay, S.A. (2000). Cryptochromes are required for phytochrome signaling to the circadian clock but not for rhythmicity. Plant Cell 12, 2499-2510 [Full text 204k]

Devlin, P.F. and Kay, S.A. (2000). Flower arranging in Arabidopsis. Science 288,1600-1602

Devlin, P.F. and Kay, S.A. (1999). Blues News. Trends Cell Biol. 9, 384.

Devlin, P.F. and Kay, S.A. (1999). Cryptochromes - bringing the blues to circadian rhythms. Trends Cell Biol. 9, 295-298 [Full text 310k]

Devlin, P.F., Robson, P.R., Patel, S.R., Goosey, L., Sharrock, R.A. and Whitelam, G.C. (1999). Phytochrome D acts in the shade-avoidance syndrome in Arabidopsis by controlling elongation growth and flowering time. Plant Physiol. 119, 909-915 [Full text 307k]

Somers, D.E., Devlin, P.F. and Kay, S.A. (1998). Phytochromes and cryptochromes in the entrainment of the Arabidopsis circadian clock. Science 282, 1488-1490 [Full text 673k]

Devlin, P.F., Patel, S.R. and Whitelam, G.C. (1998). Phytochrome E influences internode elongation and flowering time in Arabidopsis. Plant Cell 10, 1479-1487 [Full text 235k]

Sineshchekov, V.A., Ogorodnikova, O.B., Devlin, P.F. and Whitelam, G.C. (1998). Fluorescence spectroscopy and photochemistry of phytochromes A and B in wild-type, mutant and transgenic strains of Arabidopsis thaliana. Journal of Photochemistry & Photobiology B - Biology 42, 133-142.

Whitelam, G.C., Patel, S. and Devlin, P.F. (1998). Phytochromes and photomorphogenesis in Arabidopsis. Philos. Trans. R. Soc. Lond. [Biol.] 353, 1445-1453.

Whitelam, G.C. and Devlin, P.F. (1998). Light signalling in Arabidopsis. Plant Physiol. Biochem. 36, 125-133 [Full text 842k]

Devlin, P.F., Halliday, K.J. and Whitelam, G.C. (1997). The phytochrome family and their role in the regulation of seed germination. In Basic and applied aspects of seed biology. R.H. Ellis, M. Black, A.J. Murdoch, and T.D. Hong, eds. (Dordrecht: Kluwer Academic Publishers), pp. 159-171.

Devlin, P.F., Somers, D.E., Quail, P.H. and Whitelam, G.C. (1997). The Brassica rapa elongated internode (EIN) gene encodes phytochrome B. Plant Molecular Biology 34, 537-547.

Whitelam, G.C. and Devlin, P.F. (1997). Roles of different phytochromes in Arabidopsis photomorphogenesis. Plant Cell Environ. 20, 752-758.

Whitelam, G.C. and Devlin, P.F. (1996). Novel phytochromes control germination and end-of-day far-red light responses of Arabidopsis thaliana. In Regulation of plant growth and development by light. W.R. Briggs, R.L. Heath, and E.M. Tobin, eds. (Rockville, Maryland: American Society of Plant Physiologists), pp. 171-179.

Halliday, K., Devlin, P.F., Whitelam, G.C., Hanhart, C. and Koornneef, M. (1996). The ELONGATED gene of Arabidopsis acts independently of light and gibberellins in the control of elongation growth. Plant Journal 9, 305-312.

Devlin, P.F., Halliday, K.J., Harberd, N.P. and Whitelam, G.C. (1996). The rosette habit of Arabidopsis thaliana is dependent upon phytochrome action: Novel phytochromes control internode elongation and flowering time. Plant Journal 10, 1127-1134