A new type of mutation in phytochrome A causes enhanced light sensitivity and alters the degradation and subcellular partitioning of the photoreceptor

Dieterle, Monika; Bauer, Diana; Büche, Claudia; Krenz, Martina; Schäfer, Eberhard; Kretsch, Thomas

doi:10.1111/j.1365-313x.2004.02286.x

Cited by 23 publications

(35 citation statements)

References 56 publications

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“…It was shown earlier that phyA, like other phytochromes, translocates to the nucleus after Pfr formation (Kircher et al, 1999Kim et al, 2000). It was also published that phyA degradation, although not limited to the nucleus (Dieterle et al, 2005), occurs faster after nuclear translocation (Debrieux and Fankhauser, 2010;Toledo-Ortiz et al, 2010). In order to examine the possibility that phyA-5 mislocalization can be the reason for the observed phenotype, we examined the intracellular localization of phyA-5-YFP, a protein perfectly reconstituting the phyA-5 phenotype (Fig.…”

Section: Discussionmentioning

confidence: 99%

Missense Mutation in the Amino Terminus of Phytochrome A Disrupts the Nuclear Import of the Photoreceptor

et al. 2011

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Phytochromes are the red/far-red photoreceptors in higher plants. Among them, phytochrome A (PHYA) is responsible for the far-red high-irradiance response and for the perception of very low amounts of light, initiating the very-low-fluence response. Here, we report a detailed physiological and molecular characterization of the phyA-5 mutant of Arabidopsis (Arabidopsis thaliana), which displays hyposensitivity to continuous low-intensity far-red light and shows reduced very-low-fluence response and high-irradiance response. Red light-induced degradation of the mutant phyA-5 protein appears to be normal, yet higher residual amounts of phyA-5 are detected in seedlings grown under low-intensity far-red light. We show that (1) the phyA-5 mutant harbors a new missense mutation in the PHYA amino-terminal extension domain and that (2) the complex phenotype of the mutant is caused by reduced nuclear import of phyA-5 under low fluences of far-red light. We also demonstrate that impaired nuclear import of phyA-5 is brought about by weakened binding affinity of the mutant photoreceptor to nuclear import facilitators FHY1 (for FAR-RED ELONGATED HYPOCOTYL1) and FHL (for FHY1-LIKE). Finally, we provide evidence that the signaling and degradation kinetics of constitutively nuclear-localized phyA-5 and phyA are identical. Taken together, our data show that aberrant nucleo/cytoplasmic distribution impairs light-induced degradation of this photoreceptor and that the amino-terminal extension domain mediates the formation of the FHY1/FHL/PHYA far-redabsorbing form complex, whereby it plays a role in regulating the nuclear import of phyA.

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Section: Discussionmentioning

confidence: 99%

Missense Mutation in the Amino Terminus of Phytochrome A Disrupts the Nuclear Import of the Photoreceptor

et al. 2011

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“…The two PAS domain sites, D108T and E121P, occur between a2 and a3 ( Figure 3C); D108T occurs at the same position as a loss-of-function mutation in oat phyA and two residues away from an Arabidopsis mutant with reduced protein stability . One of the two GAF a5 sites, R231F, is two residues away from the eid4 mutant, which is hypersensitive to FR and has increased stability in light (Dieterle et al, 2005). Three residues map to the GAF loop, two of which when mutated in pea or oat, lead to a blue shift in the absorption maximum or to reduced rate of chromophore ligation, respectively ( Figure 3C; Deforce et al, 1993;Kim et al, 2007).…”

Section: Changes On the Na And A Branchesmentioning

confidence: 99%

Evolutionary Studies Illuminate the Structural-Functional Model of Plant Phytochromes

Mathews

2010

The Plant Cell

107

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A synthesis of insights from functional and evolutionary studies reveals how the phytochrome photoreceptor system has evolved to impart both stability and flexibility. Phytochromes in seed plants diverged into three major forms, phyA, phyB, and phyC, very early in the history of seed plants. Two additional forms, phyE and phyD, are restricted to flowering plants and Brassicaceae, respectively. While phyC, D, and E are absent from at least some taxa, phyA and phyB are present in all sampled seed plants and are the principal mediators of red/far-red-induced responses. Conversely, phyC-E apparently function in concert with phyB and, where present, expand the repertoire of phyB activities. Despite major advances, aspects of the structural-functional models for these photoreceptors remain elusive. Comparative sequence analyses expand the array of locus-specific mutant alleles for analysis by revealing historic mutations that occurred during gene lineage splitting and divergence. With insights from crystallographic data, a subset of these mutants can be chosen for functional studies to test their importance and determine the molecular mechanism by which they might impact light perception and signaling. In

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“…The phyA eid4 allele (E229K) is hypersensitive to FR and shows normal PHYA protein levels and phyA spectral activity (47). The phyA-110 mutant (R279S) retains WT protein levels and has been proposed to produce a P fr intermediate unable to form the P r state (48).…”

Section: Discussionmentioning

confidence: 99%

Functional and Biochemical Analysis of the N-terminal Domain of Phytochrome A

Mateos

Luppi

Ogorodnikova

et al. 2006

Journal of Biological Chemistry

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Phytochrome A (phyA) is a versatile plant photoreceptor that mediates responses to brief light exposures (very low fluence responses, VLFR) as well as to prolonged irradiation (high irradiance responses, HIR). We identified the phyA-303 mutant allele of Arabidopsis thaliana bearing an R384K substitution in the GAF subdomain of the N-terminal half of phyA. phyA-303 showed reduced phyA spectral activity, almost normal VLFR, and severely impaired HIR. Recombinant N-terminal half oat of PHYA bearing the phyA-303 mutation showed poor incorporation of chromophore in vitro, despite the predicted relatively long distance (>13 Å ) between the mutation and the closest ring of the chromophore. Fusion proteins bearing the N-terminal domain of oat phyA, ␤-glucuronidase, green fluorescent protein, and a nuclear localization signal showed physiological activity in darkness and mediated VLFR but not HIR. At equal protein levels, the phyA-303 mutation caused slightly less activity than the fusions containing the wild-type sequence. Taken together, these studies highlight the role of the N-terminal domain of phyA in signaling and of distant residues of the GAF subdomain in the regulation of phytochrome bilin-lyase activity.Plant photoreceptors monitor the cues provided by the light environment and trigger modifications that adjust growth and development to the prevailing conditions (1, 2). Phytochromes are sensors of red and far-red (FR) 3 light that bind an open chain tetrapyrrole chromophore (3, 4). Arabidopsis thaliana bears five phytochrome apoprotein genes (PHYA through PHYE) (5). phyA is a versatile photoreceptor that induces seed germination in response to brief exposures to light (6, 7), which the seeds may experience during soil labor. phyA is also required to perceive the prolonged exposures to FR that the seedlings experience when they emerge from the soil under dense plant canopies (8). These two photoresponses mediated by phyA are of the types called very low fluence responses (VLFR) and high irradiance responses (HIR), respectively (9). Some physiological processes (e.g. inhibition of hypocotyl growth, unfolding of the cotyledons) exhibit both VLFR and HIR as two discrete phases of response, where VLFR saturates with infrequent FR pulses and HIR requires very frequent or continuous FR (10). HIR requires cis-acting elements at target gene promoters (11) and domains of the phyA molecule itself (12) that are dispensable for VLFR.The N-terminal domain of phytochromes bears the chromophore attachment site (13) and provides differential spectral selectivity to phyA (more active under FR than red light) compared with phyB (more active under red light than FR) (14). The C-terminal domain contains a histidine kinase-related sequence motif that is able to mediate phosphorylation (15, 16), two PAS (domain named after Per, Arnt, and Sim) motifs important for downstream signaling in the context of the full molecule (17), and residues necessary for dimerization (18,19) and targeting to the nucleus upon light activation (20, 21)...

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A new type of mutation in phytochrome A causes enhanced light sensitivity and alters the degradation and subcellular partitioning of the photoreceptor

Cited by 23 publications

References 56 publications

Missense Mutation in the Amino Terminus of Phytochrome A Disrupts the Nuclear Import of the Photoreceptor

Missense Mutation in the Amino Terminus of Phytochrome A Disrupts the Nuclear Import of the Photoreceptor

Evolutionary Studies Illuminate the Structural-Functional Model of Plant Phytochromes

Functional and Biochemical Analysis of the N-terminal Domain of Phytochrome A

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