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IN BRIEF

Dominant, Constitutively Active Phytochrome Mutants

neckardt{at}aspb.org

Signaling via the red/far-red phytochrome photoreceptors regulates many aspects of plant growth and development. The dicot Arabidopsis possesses five different types of phytochromes, PHYA-E, which exhibit overlapping and distinct functions. Phytochromes (principally phyB) are well known for their photoreversibility: absorption of red light converts phyB to the physiological active (signaling) state, whereas far-red absorption converts it back to an inactive state.

Su and Lagarias (pages 2124–2139) report the discovery of a new class of Arabidopsis phytochrome mutants that exhibit light-independent constitutive signaling. Dominant gain-of-function activity is conferred by mutation of a conserved GAF domain Tyr residue (Y^GAF) that is critical for photoactivation of plant phytochromes. Although phyB Y^GAF mutants (B^Y276H) were poorly photoreactive, they exhibited constitutive signaling activity by conferring light-independent seed germination, activation of light-regulated genes, and constitutive photomorphogenic development. Results of this study thus demonstrate a key role of Y^GAF in coupling light perception with downstream signaling. In addition, the identification of constitutively active alleles of plant phytochromes holds potential for crop improvement. The phytochrome-mediated shade avoidance syndrome contributes significantly to yield losses in high-density crop plantings, losses that might be mitigated by expression of these novel gain-of-function alleles in crop species.

View larger version (86K): [in this window] [in a new window] [as a PowerPoint slide]   Dark-grown plants expressing BY276H show light-grown development compared with the wild type (Ler) and plants expressing wild-type PHYB (B).

www.plantcell.org/cgi/doi/10.1105/tpc.107.190711

Related articles in Plant Cell:

Light-Independent Phytochrome Signaling Mediated by Dominant GAF Domain Tyrosine Mutants of Arabidopsis Phytochromes in Transgenic Plants

Yi-shin Su and J. Clark Lagarias
Plant Cell 2007 19: 2124-2139. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Cell Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eckardt, N. A. Search for Related Content PubMed Articles by Eckardt, N. A. Agricola Articles by Eckardt, N. A.