The amino‐terminus of phytochrome A contains two distinct functional domains

• Published in: The Plant journal : for cell and molecular biology Vol. 9; no. 2; pp. 243 - 257
• Main Authors: Jordan, Emily T., Cherry, Joel R., Walker, Joseph M., Vierstra, Richard D.
• Format: Journal Article
• Language: English
• Published: Osney Mead, Oxford OX2 0EL, UK Blackwell Science Ltd 01.02.1996; Blackwell Science
• Subjects: Amino Acid Sequence; Avena - genetics; Base Sequence; Biological and medical sciences; Chromatography, Affinity; DNA Mutational Analysis; Dose-Response Relationship, Radiation; Fundamental and applied biological sciences. Psychology; Light; Metabolism; Molecular Sequence Data; Mutagenesis, Site-Directed; Nicotiana - genetics; Nicotiana - growth & development; Nicotiana - radiation effects; Nicotiana tabacum; Phenotype; Phytochrome - physiology; Phytochrome A; Plant physiology and development; Plants, Genetically Modified - growth & development; Plants, Genetically Modified - radiation effects; Plants, Toxic; Sequence Deletion; Species Specificity; Spectrophotometry; Storage and secretion, pigments, phytochrome; Structure-Activity Relationship; Photoreceptor; Red light; Gene expression; Nicotiana tabacum; Structure function relationship; Phenotype; Dicotyledones; Angiospermae; Phytochrome; N terminal-Sequence; Deletion; Spermatophyta; Transgenic plant; Solanaceae; Experimental plant; Molecular domain; Aminoacid sequence
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1996.09020243.x

The N‐terminus of phytochrome A is important for the structural integrity and biological activity of the photoreceptor. Mutational analysis of the N‐terminus by two different strategies created two distinct photoreceptors, one inactive and the other hyperactive when expressed in transgenic tobacco, suggesting that this region has multiple functional domains. To identify critical residues within this N‐terminal region, a series of smaller deletions of oat phytochrome A were created, designated NB (Δ49–62), NC (Δ6–47), ND (Δ7–21), NE (Δ2–5), and NF (Δ6–12), and compared with a previously characterized deletion mutant NA (Δ7–69) and full‐length oat phytochrome A. Using photochemical properties as a measure of chromoprotein structure, it was found that the region between residues 13 and 62 was important for the spectral integrity of the photoreceptor. These deletion mutants were also biologically inactive when expressed in both mature tobacco plants and seedlings grown under continuous far‐red or red light. In contrast, deletion of the serine‐rich region between residues 6 and 12 did not alter the photochemical properties but did produce a hyperactive photoreceptor, indicating this region may be involved in down‐regulating phytochrome A activity. The data show that the N‐terminus of phytochrome A contains two functional domains, one necessary for conformational stability and biological activity (residues 13–62), and the other involved in attenuating phytochrome responses (residues 6–12).