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. 1996 Sep;112(1):291–296. doi: 10.1104/pp.112.1.291

Mutations of Arabidopsis in potential transduction and response components of the phototropic signaling pathway.

E Liscum 1, W R Briggs 1
PMCID: PMC157948  PMID: 8819327

Abstract

Four genetic loci were recently identified by mutations that affect phototropism in Arabidopsis thaliana (L.) Heyhn. seedlings. It was hypothesized that one of these loci, NPH1, encodes the apoprotein for a phototropic photoreceptor. All of the alleles at the other three mutant loci (nph2, nph3, and nph4) contained wild-type levels of the putative NPH1 protein and exhibited normal blue-light-dependent phosphorylation of the NPH1 protein. This indicated that the NPH2, NPH3, and NPH4 proteins likely function downstream of NPH1 photoactivation. We show here that, although the nph2, nph3, and nph4 mutants are all altered with respect to their phototropic responses, only the nph4 mutants are also altered in their gravitropic responsiveness. Thus, NPH2 and NPH3 appear to act as signal carriers in a phototropism-specific pathway, whereas NPH4 is required for both phototropism and gravitropism and thus may function directly in the differential growth response. Despite their altered phototropic responses in blue and green light as etiolated seedlings, the nph2 and nph4 mutants exhibited less dramatic mutant phenotypes as de-etiolated seedlings and when etiolated seedlings were irradiated with unilateral ultraviolet-A (UV-A) light. Examination of the phototropic responses of a mutant deficient in biologically active phytochromes, hy1-100, indicated that phytochrome transformation by UV-A light mediates an increase in phototropic responsiveness, accounting for the greater phototropic curvature of the nph2 and nph4 mutants to UV-A light than to blue light.

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Selected References

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  1. Chory J., Peto C. A., Ashbaugh M., Saganich R., Pratt L., Ausubel F. Different Roles for Phytochrome in Etiolated and Green Plants Deduced from Characterization of Arabidopsis thaliana Mutants. Plant Cell. 1989 Sep;1(9):867–880. doi: 10.1105/tpc.1.9.867. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Khurana J. P., Poff K. L. Mutants of Arabidopsis thaliana with altered phototropism. Planta. 1989;178:400–406. [PubMed] [Google Scholar]
  3. Khurana J. P., Ren Z., Steinitz B., Parks B., Best T. R., Poff K. L. Mutants of Arabidopsis thaliana with decreased amplitude in their phototropic response. Plant Physiol. 1989;91:685–689. doi: 10.1104/pp.91.2.685. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Lin C., Ahmad M., Gordon D., Cashmore A. R. Expression of an Arabidopsis cryptochrome gene in transgenic tobacco results in hypersensitivity to blue, UV-A, and green light. Proc Natl Acad Sci U S A. 1995 Aug 29;92(18):8423–8427. doi: 10.1073/pnas.92.18.8423. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Liscum E., Briggs W. R. Mutations in the NPH1 locus of Arabidopsis disrupt the perception of phototropic stimuli. Plant Cell. 1995 Apr;7(4):473–485. doi: 10.1105/tpc.7.4.473. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Liscum E., Young J. C., Poff K. L., Hangarter R. P. Genetic separation of phototropism and blue light inhibition of stem elongation. Plant Physiol. 1992 Sep;100(1):267–271. doi: 10.1104/pp.100.1.267. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Malhotra K., Kim S. T., Batschauer A., Dawut L., Sancar A. Putative blue-light photoreceptors from Arabidopsis thaliana and Sinapis alba with a high degree of sequence homology to DNA photolyase contain the two photolyase cofactors but lack DNA repair activity. Biochemistry. 1995 May 23;34(20):6892–6899. doi: 10.1021/bi00020a037. [DOI] [PubMed] [Google Scholar]
  8. Nagatani A., Reed J. W., Chory J. Isolation and Initial Characterization of Arabidopsis Mutants That Are Deficient in Phytochrome A. Plant Physiol. 1993 May;102(1):269–277. doi: 10.1104/pp.102.1.269. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Parker K., Baskin T. I., Briggs W. R. Evidence for a phytochrome-mediated phototropism in etiolated pea seedlings. Plant Physiol. 1989 Feb;89(2):493–497. doi: 10.1104/pp.89.2.493. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Parks B. M., Quail P. H., Hangarter R. P. Phytochrome A regulates red-light induction of phototropic enhancement in Arabidopsis. Plant Physiol. 1996 Jan;110(1):155–162. doi: 10.1104/pp.110.1.155. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Parks B. M., Quail P. H. Phytochrome-Deficient hy1 and hy2 Long Hypocotyl Mutants of Arabidopsis Are Defective in Phytochrome Chromophore Biosynthesis. Plant Cell. 1991 Nov;3(11):1177–1186. doi: 10.1105/tpc.3.11.1177. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Pratt L. H., Briggs W. R. Photochemical and Nonphotochemical Reactions of Phytochrome in vivo. Plant Physiol. 1966 Mar;41(3):467–474. doi: 10.1104/pp.41.3.467. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Reymond P., Short T. W., Briggs W. R., Poff K. L. Light-induced phosphorylation of a membrane protein plays an early role in signal transduction for phototropism in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 1992 May;89(10):4718–4721. doi: 10.1073/pnas.89.10.4718. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Short T. W., Briggs W. R. Characterization of a Rapid, Blue Light-Mediated Change in Detectable Phosphorylation of a Plasma Membrane Protein from Etiolated Pea (Pisum sativum L.) Seedlings. Plant Physiol. 1990 Jan;92(1):179–185. doi: 10.1104/pp.92.1.179. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Steinitz B., Ren Z., Poff K. L. Blue and Green Light-Induced Phototropism in Arabidopsis thaliana and Lactuca sativa L. Seedlings. Plant Physiol. 1985 Jan;77(1):248–251. doi: 10.1104/pp.77.1.248. [DOI] [PMC free article] [PubMed] [Google Scholar]

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