Journal Article

Cryptochromes and Phytochromes Synergistically Regulate <i>Arabidopsis</i> Root Greening under Blue Light

Takeshi Usami, Nobuyoshi Mochizuki, Maki Kondo, Mikio Nishimura and Akira Nagatani

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 12, pages 1798-1808
Published in print December 2004 | ISSN: 0032-0781
Published online December 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch205
Cryptochromes and Phytochromes Synergistically Regulate Arabidopsis Root Greening under Blue Light

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To increase their fitness, plants sense ambient light conditions and modulate their developmental processes by utilizing multiple photoreceptors such as phytochrome, cryptochrome and phototropin. Even roots, which are normally not exposed to light, express photoreceptors and can respond to light by developing chloroplasts. In the present study, root greening was observed in Arabidopsis thaliana. Seedlings were grown under monochromatic light and chlorophyll levels in the roots were determined. It was found that blue light was far more effective at inducing chloroplast development in Arabidopsis roots than was red light, and this response was under the control of a strong synergistic interaction between phytochromes and cryptochromes. As expected, the cry1 mutant was deficient in this response. Interestingly, the phyAphyB double mutant failed to respond to blue light under these conditions. This strongly suggests that either phytochrome A or phytochrome B, in addition to cryptochrome, was required for this blue light response. It was further demonstrated that the expression of photosynthetic genes was regulated in the same way. Dichromatic irradiation experiments indicated that this interaction depends on the level of phyB PFR. Analysis of the cop1, det1 and hy5 mutants indicated that the corresponding factors were involved in the response.

Keywords: Keywords: Arabidopsis thaliana — Chloroplast development — Cryptochrome — Gene expression — Phytochrome — Root.; Abbreviations: cry1, cryptochrome 1; cry2, cryptochrome 2; Ler, ecotype Landsberg erecta; phyA, phytochrome A; phyB, phytochrome B; RT-PCR, reverse transcription-polymerase chain reaction.

Journal Article.  6959 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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