title: Coordination of phytochrome levels in phyB mutants of Arabidopsis as revealed by apoprotein-specific monoclonal antibodies.
abstract: Accumulating evidence indicates that individual members of the phytochrome family of photoreceptors have differential but interactive roles in controlling plant responses to light. To investigate possible cross-regulation of these receptors, we have identified monoclonal antibodies that specifically detect each of the five Arabidopsis phytochromes, phyA to phyE (phytochrome A holoprotein; PHYA, phytochrome A apoprotein; PHYA, phytochrome A gene; phyA, mutant allele of phytochrome A gene), on immunoblots and have used them to analyze the effects of phyA and phyB null mutations on the levels of all five family members. In phyB mutants, but not in phyA mutants, a four- to six-fold reduction in the level of phyC is observed in tissues grown either in the dark or in the light. Coordinate expression of phyB and phyC is induced in the phyB mutant background by the presence of a complementing PHYB transgene. However, in transgenic lines that overexpress phyB 15- to 20-fold, phyC is not similarly overexpressed. In these overexpressor lines, the levels of phyA, phyC, and phyD are increased two- to four-fold over normal in light-grown but not dark-grown seedlings. These observations indicate that molecular mechanisms for coordination or cross-regulation of phytochrome levels are active in Arabidopsis and have implications for the interpretation of phytochrome mutants and overexpressor lines.
authors.affiliation: Department of Biology, Montana State University, Bozeman, Montana 59717, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hirschfeld
authors.forename: J M
authors.initials: JM
authors.lastname: Tepperman
authors.forename: T
authors.initials: T
authors.lastname: Clack
authors.forename: P H
authors.initials: PH
authors.lastname: Quail
authors.forename: R A
authors.initials: RA
authors.lastname: Sharrock
mesh_terms: D000911:Antibodies, Monoclonal / Q000302:isolation & purification / Q000378:metabolism*; D000918:Antibody Specificity; D001059:Apoproteins / Q000032:analysis / Q000276:immunology* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins; D018506:Gene Expression Regulation, Plant; D015151:Immunoblotting; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics*; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D051942:Phytochrome A; D051939:Phytochrome B; D010940:Plant Proteins / Q000032:analysis; D012323:RNA Processing, Post-Transcriptional; D014157:Transcription Factors
chemical_list: D000911:Antibodies, Monoclonal; D001059:Apoproteins; D029681:Arabidopsis Proteins; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D010940:Plant Proteins; D014157:Transcription Factors; C406683:phytochrome C, Arabidopsis; D010834:Phytochrome; D051939:Phytochrome B; C088754:PHYD protein, Arabidopsis