Disease relevance of PHOT1

• Here, we have transformed the phot1 phot2 (phot1-5 phot2-1) double mutant with PHOT expression constructs driven by the cauliflower mosaic virus 35S promoter [1].
• Moreover, the data obtained from full-length Arabidopsis phot1 and phot2 expressed in insect cells closely resemble those obtained for the tandem LOV-domain fusion proteins expressed in E. coli [2].
• A prokaryotic protein, YtvA from Bacillus subtilis, was found to possess a light, oxygen, voltage (LOV) domain sharing high homology with the photoactive, flavin mononucleotide (FMN)-binding LOV domains of phototropins (phot), blue-light photoreceptors for phototropism in higher plants [3].

High impact information on PHOT1

• The PAS region is highly similar to the PAS domain of the Arabidopsis blue-light receptor NPH1, and the Neurospora circadian-associated protein WHITE COLLAR-1 (WC-1) [4].
• The fern Adiantum capillus-veneris has an unconventional photoreceptor, phytochrome 3 (phy3), which is a chimaera of the red/far-red light receptor phytochrome and phototropin [5].
• Phototropin-related NPL1 controls chloroplast relocation induced by blue light [6].
• Arabidopsis NPH3: A NPH1 photoreceptor-interacting protein essential for phototropism [7].
• Phototropism of Arabidopsis thaliana seedlings in response to a blue light source is initiated by nonphototropic hypocotyl 1 (NPH1), a light-activated serine-threonine protein kinase [7].

Biological context of PHOT1

• In Arabidopsis thaliana, phototropism of seedling and plant stems is under the control of two paralogous genes, PHOT1 and PHOT2, that encode different phototropins with partially redundant light response qualities [8].
• In vitro experiments indicate that cross phosphorylation can occur between functional phot2 and inactivated phot1 molecules [1].
• Similarly, transformants carrying a PHOT transgene with both LOV domains inactivated developed strong curvatures toward high fluence rate blue light [1].
• Surprisingly, the only significant genotype-by-environment interaction for fitness occurred during emergence: genotypes blind to dim blue light (phot1 and nph3) had poor emergence in the open, but not in the shade [8].
• Consistent with their different fluence rate sensitivities, phot1 and phot2 signaling pathways affected fitness at discrete life-cycle stages [8].

Anatomical context of PHOT1

• The Arabidopsis gene NPL1 (ref. 2) is a paralogue of the NPH1 gene, which encodes phototropin, a photoreceptor for phototropic bending [6].
• Although phot1 is localized consistently to the plasma membrane region in etiolated seedlings, a fraction becomes released to the cytoplasm in response to blue light [9].
• Moreover, increased ATP hydrolysis and the binding of 14-3-3 protein to the H+-ATPase were found in response to blue light in guard cell protoplasts from the wild type, but not from the phot1 phot2 double mutant [10].

Associations of PHOT1 with chemical compounds

• It is suggested that PHOT1 regulates Ca(2+) uptake into the cytoplasm from the apoplast [11].
• Phototropin 1 (phot1) is a Ser/Thr photoreceptor kinase that binds two molecules of flavin mononucleotide as its chromophores and undergoes autophosphorylation in response to blue light [9].
• Phototropins (phot1 and phot2) are autophosphorylating serine/threonine kinases that function as photoreceptors for phototropism, light-induced chloroplast movement, and stomatal opening in Arabidopsis [12].
• 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) [12].
• Phototropin has two chromophoric domains named light-oxygen-voltage-sensing (LOV) 1 and 2 in the N-terminal half, and a serine/threonine (Ser/Thr) protein kinase motif in the C-terminal half [13].

Physical interactions of PHOT1

• The PHOT1 gene product interacts with the NPH3 gene product to cause phototropic bending over a broad range of light intensity, from very weak light in the soil to stronger light in the aerial environment [8].

Regulatory relationships of PHOT1

• This result indicates that BL-activation of phototropin influences cryptochrome signaling leading to growth inhibition [14].
• The enhancement of phototropin-induced phototropic curvature in Arabidopsis occurs via a photoreversible phytochrome A-dependent modulation of auxin responsiveness [15].

Other interactions of PHOT1

• RPT2 is a signal transducer involved in phototropic response and stomatal opening by association with phototropin 1 in Arabidopsis thaliana [16].
• There is evidence only for the phototropin blue light receptors (PHOT1 and PHOT2) in mediating blue light regulation of stomatal opening [17].
• Only NONPHOTOTROPIC HYPOCOTYL 3 (NPH3) and root phototropism 2, both belonging to the same family of proteins, have been previously identified as phototropin-interacting signal transducers involved in phototropism [18].
• PHYTOCHROME KINASE SUBSTRATE 1 is a phototropin 1 binding protein required for phototropism [18].
• An auxilin-like J-domain protein, JAC1, regulates phototropin-mediated chloroplast movement in Arabidopsis [19].

Analytical, diagnostic and therapeutic context of PHOT1

• Thus, these results suggest that phot1 and phot2 choose different signal transducers to induce three responses: phototropic response of hypocotyl, stomatal opening, and chloroplast relocation [16].
• These results unravel the stoma autonomous function in the blue light response and illuminate the implication of PHOT1 and/or PHOT2 in such response [20].
• These structural homologies indicate that NPH1 homologues can be grouped into two classes namely "NPH1 type" and "NPL1 type". Northern blot analysis showed that OsNPH1a was strongly expressed in coleoptiles, whereas OsNPH1b was highly expressed in leaves of dark-grown rice seedlings [21].
• In this study, we compared light-induced structural changes of the LOV1 and LOV2 domains of a phototropin, Adiantum phytochrome3 (phy3), by means of UV-visible and Fourier transform infrared (FTIR) spectroscopy [22].

References