Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

• Published in: Plant, cell and environment Vol. 31; no. 12; pp. 1756 - 1770
• Main Authors: WARPEHA, KATHERINE M, GIBBONS, JACK, CAROL, ANDREW, SLUSSER, JAMES, TREE, ROGER, DURHAM, WILLIAM, KAUFMAN, LON S
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.12.2008; Blackwell Publishing Ltd; Blackwell
• Subjects: Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis - radiation effects; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biological and medical sciences; Cotyledon - genetics; Cotyledon - metabolism; Cotyledon - radiation effects; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; GTP-Binding Protein alpha Subunits - genetics; GTP-Binding Protein alpha Subunits - metabolism; Mutagenesis, Insertional; Mutation; Phenylalanine - biosynthesis; phenylpropanoid; prephenate dehydratase; Receptors, G-Protein-Coupled - genetics; Receptors, G-Protein-Coupled - metabolism; RNA, Plant - genetics; Seedlings - genetics; Seedlings - metabolism; Seedlings - radiation effects; Signal Transduction; Ultraviolet Rays; UV‐A; UV‐absorbing compounds; UV‐B; phenylpropanoid; Phenylpropanoid pathway; Phenylalanine; UVB radiation; Plant juvenile growth stage; Plant ecology; Ultraviolet absorption; Etiolation; Sporophyte; Arabidopsis thaliana; UV-B; Ultraviolet radiation; UV-A; UV-absorbing compounds; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Experimental plant; Damage; G protein; prephenate dehydratase
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2008.01878.x

Etiolated Arabidopsis thaliana seedlings, lacking a functional prephenate dehydratase1 gene (PD1), also lack the ability to synthesize phenylalanine (Phe) and, as a consequence, phenylpropanoid pigments. We find that low doses of ultraviolet (UV)-C (254 nm) are lethal and low doses of UV-B cause severe damage to etiolated pd1 mutants, but not to wild-type (wt) seedlings. Furthermore, exposure to UV-C is lethal to etiolated gcr1 (encoding a putative G protein-coupled receptor in Arabidopsis) mutants and gpa1 (encoding the sole G protein α subunit in Arabidopsis) mutants. Addition of Phe to growth media restores wt levels of UV resistance to pd1 mutants. The data indicate that the Arabidopsis G protein-signalling pathway is critical to providing protection from UV, and does so via the activation of PD1, resulting in the synthesis of Phe. Cotyledons of etiolated pd1 mutants have proplastids (compared with etioplasts in wt), less cuticular wax and fewer long-chain fatty acids. Phe-derived pigments do not collect in the epidermal cells of pd1 mutants when seedlings are treated with UV, particularly at the cotyledon tip. Addition of Phe to the growth media restores a wt phenotype to pd1 mutants.