Ultraviolet B Radiation Enhances a Phytochrome-B-Mediated Photomorphogenic Response in Arabidopsis

Abstract

Ultraviolet B radiation (UV-B, 290-315 nm) can cause damage and induce photomorphogenic responses in plants. The mechanisms that mediate the photomorphogenic effects of UV-B are unclear. In etiolated Arabidopsis seedlings, a daily exposure to 2.5 h of UV-B enhanced the cotyledon opening response induced by a subsequent red light (R) pulse. An R pulse alone, 2.5 h of UV-B terminated with a far-red pulse, or 2.5 h of continuous R caused very little cotyledon opening. The enhancing effect of UV-B increased with fluence rate up to approximately 7.58 mol m Ϫ2 s Ϫ1 ; at higher fluence rates the response to UV-B was greatly reduced. The phyA, phyA cry1, and cry1 cry2 mutants behaved like the wild type when exposed to UV-B followed by an R pulse. In contrast, phyB, phyB cry1, and phyB phyA mutants failed to open the cotyledons. Thus, phytochrome B was required for the cotyledon opening response to UV-B 3 R treatments, whereas phytochrome A and cryptochromes 1 and 2 were not necessary under the conditions of our experiments. The enhancing effect of low doses of UV-B on cotyledon opening in uvr1 uvr2 and uvr1 uvr3 mutants, deficient in DNA repair, was similar to that found in the wild type, suggesting that this effect of UV-B was not elicited by signals derived from UV-B-induced DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts). We conclude that low doses of UV-B, perceived by a receptor system different from phytochromes, cryptochromes, or DNA, enhance a de-etiolation response that is induced by active phytochrome B.

The UVR8 UV-B Photoreceptor: Perception, Signaling and Response

“…Wellmann 1976, Ballare et al 1991, Beggs and Wellmann 1994, Ballare et al 1995, Frohnmeyer et al 1999, with more recent reports focussed on Arabidopsis (e.g. Christie and Jenkins 1996, Kim et al 1998, Boccalandro et al 2001, Brosche et al 2002, Ulm et al 2004, Brown et al 2005, Favory et al 2009). However, prior to the molecular identification of UVR8 as the UV-B photoreceptor in Information from a large part of the solar spectrum is perceived by the currently known 13 plant photoreceptors in Arabidopsis and used to deploy wavelength-specific responses.…”

Increased Phytochrome B Alleviates Density Effects on Tuber Yield of Field Potato Crops

“…Proteins were extracted from 100 mg of leaves taken from the upper strata of the canopy of field-grown plants by following the method of Martinez-García et al (1999). PAGE and antibodies probing were conducted as described by Boccalandro et al (2001). Band intensity (both PHYB-associated alkaline phosphatase activity and total protein Ponceau S reversible staining) was quantified with an imager system (Fluor-S Multimager, Bio-Rad, Hercules, CA).…”

CONSTITUTIVELY PHOTOMORPHOGENIC1 Is Required for the UV-B Response in Arabidopsis

“…The blue and red/far-red range of the visible solar spectrum is monitored by cryptochrome, phototropin, and phytochrome photoreceptors (e.g., Chen et al, 2004), but no photoreceptor(s) specialized to sensing UV-B radiation has yet been identified at the molecular level in plants or any other organism. However, in contrast with animals, for plants, UV-B irradiation is not a mere stress signal but can also serve as an environmental stimulus to direct growth and development (Kim et al, 1998;Boccalandro et al, 2001;Kliebenstein et al, 2002;Brosche and Strid, 2003;Frohnmeyer and Staiger, 2003;Paul and Gwynn-Jones, 2003;Suesslin and Frohnmeyer, 2003;Ulm and Nagy, 2005). This includes hypocotyl growth inhibition, flavonoid accumulation, and specific gene expression changes.…”