Poster: Photomorphogenesis

Abs # 496: The Role of Phytochrome C in Arabidopsis Photomorphogenesis

Presenter:	Franklin, Keara A, kaf5@le.ac.uk
Authors	Franklin, Keara A (A)   Davis, Seth J (B) (C)  Stoddart, Wendy M (A)   Vierstra, Richard D (B)   Whitelam, Garry C (A)
Affiliations:	(A): University of Leicester (B): University of Wisconsin-Madison (C): MPIZ, Cologne.

Light signals regulate plant growth and development through the action of specialised photoreceptors, the red/far-red light (R/FR) -absorbing phytochromes and the UVA/blue light (B) -absorbing cryptochromes and phototropins. In Arabidopsis, 5 discrete apophytochrome-encoding genes, PHYA-PHYE have been isolated and sequenced. PhyB, D and E are the most recently evolved members of the phytochrome family and form a distinct subgroup, while phyC is most closely related to phyA (about 50% identity). The analysis of phytochrome-deficient mutants has revealed different phytochromes to play both distinct and overlapping roles throughout plant photomorphogenesis. Until recently, the absence of a phyC mutant has precluded functional analysis of this phytochrome. Over-expression studies in both Arabidopsis and tobacco have suggested roles for phyC in leaf development. The recent isolation of a phyC mutant and the subsequent creation of mutants, deficient in multiple phytochrome combinations have revealed functional roles for phyC throughout Arabidopsis photomorphogenesis. Such work is supported by the parallel analysis of a quadruple mutant, deficient in phytochromes A, B, D and E. Despite operating as a weak red light sensor in isolation, phyC performs a significant role in the modulation of other photoreceptors. phyA and phyC act redundantly to modulate the phyB-mediated inhibition of hypocotyl elongation in R and act together to regulate mature leaf morphology. In addition, phyC performs a significant role in the modulation of blue light sensing, possibly through interaction with cryptochrome 2 (cry2).