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Phototropin LOV domains exhibit distinct roles in regulating photoreceptor function
Author(s) -
Christie John M.,
Swartz Trevor E.,
Bogomolni Roberto A.,
Briggs Winslow R.
Publication year - 2002
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2002.01415.x
Subject(s) - phototropin , phototropism , arabidopsis , flavin mononucleotide , cryptochrome , biology , variegation (histology) , abscission , biophysics , biochemistry , microbiology and biotechnology , botany , flavin group , materials science , blue light , mutant , enzyme , circadian clock , optoelectronics , gene
Summary Phototropins (phot1 and phot2) are autophosphorylating serine/threonine kinases that function as photoreceptors for phototropism, light‐induced chloroplast movement, and stomatal opening in Arabidopsis . The N‐terminal region of phot1 and phot2 contains two specialized PAS domains, designated LOV1 and LOV2, which function as binding sites for the chromophore flavin mononucleotide (FMN). Both LOV1 and LOV2 undergo a self‐contained photocycle, which involves the formation of a covalent adduct between the FMN chromophore and a conserved active‐site cysteine residue (Cys39). Replacement of Cys39 with alanine abolishes the light‐induced photochemical reaction of LOV1 and LOV2. Here we have used the Cys39Ala mutation to investigate the role of LOV1 and LOV2 in regulating phototropin function. Photochemical analysis of a bacterially expressed LOV1 + LOV2 fusion protein indicates that LOV2 functions as the predominant light‐sensing domain for phot1. LOV2 also plays a major role in mediating light‐dependent autophosphorylation of full‐length phot1 expressed in insect cells and transgenic Arabidopsis . Moreover, photochemically active LOV2 alone in full‐length phot1 is sufficient to elicit hypocotyl phototropism in transgenic Arabidopsis , whereas photochemically active LOV1 alone is not. Further photochemical and biochemical analyses also indicate that the LOV1 and LOV2 domains of phot2 exhibit distinct roles. The significance for the different roles of the phototropin LOV domains is discussed.