title: Detection of spatial-specific phytochrome responses using targeted expression of biliverdin reductase in Arabidopsis.
abstract: To regulate levels of holophytochrome in a spatial-specific manner and investigate the major sites of action of phytochromes during seedling development, we constructed transgenic Arabidopsis (Arabidopsis thaliana) plant lines expressing plastid-targeted mammalian biliverdin IXalpha reductase (pBVR) under regulatory control of CAB3 and MERI5 promoters. Comparative photobiological and phenotypic analyses indicated that spatial-specific expression of pBVR led to the disruption of distinct subsets of phytochrome-regulated responses for different promoters. pBVR expression in photosynthetic tissues (CAB3::pBVR lines) had intermediate effects on chlorophyll accumulation, carotenoid production, anthocyanin synthesis, and leaf development responses in white-light conditions. CAB3::pBVR expression, however, resulted in distinctive phenotypes in far-red (FR) conditions. A number of FR high irradiance responses were disrupted in CAB::pBVR lines, including FR-dependent inhibition of hypocotyl elongation and stimulation of anthocyanin accumulation. By contrast, preferential expression of pBVR in the shoot apical meristem in MERI5::pBVR lines resulted in a phytochrome-deficient, leaf development phenotype under short-day growth conditions. These results implicate leaf-localized phytochrome A as having a unique role in regulating FR-mediated hypocotyl elongation and meristem- and/or leaf primordia-localized phytochromes as having a novel role in phytochrome-dependent responses. Taken together, these studies demonstrate the efficacy of selectively inactivating distinct phytochrome-mediated responses by regulated expression of BVR in transgenic plants, a novel means to investigate the sites of phytochrome photoperception and to regulate specifically light-mediated plant growth and development.
authors.affiliation: Department of Energy Plant Research Laboratory , Michigan State University, East Lansing, Michigan 48824-1312, USA.
authors.forename: Sankalpi N
authors.initials: SN
authors.lastname: Warnasooriya
authors.forename: Beronda L
authors.initials: BL
authors.lastname: Montgomery
mesh_terms: D000818:Animals; D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D002734:Chlorophyll / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D018546:Hypocotyl / Q000254:growth & development / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism*; D051942:Phytochrome A / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D051942:Phytochrome A; D011994:Recombinant Proteins; D002734:Chlorophyll; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019789:biliverdin reductase