expression patterns of arabinogalactan-protein AtAGP30 and GLABRA2 reveal a role for abscisic acid in the early stages of root epidermal patterning

• Published in: The Plant journal : for cell and molecular biology 2004-07, Vol.39 (1), p.70-83
• Main Authors: van Hengel, A.J, Barber, C, Roberts, K
• Format: Article
• Language: English
• Subjects: abscisic acid; Abscisic Acid - pharmacology; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; arabinogalactan protein; arabinogalactans; beta-glucuronidase; Biological and medical sciences; cell differentiation; cell patterning; Chemical agents; epidermis; epidermis (plant); ethylene; Ethylenes - pharmacology; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant; green fluorescent protein; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; messenger RNA; molecular sequence data; Mucoproteins - genetics; Mucoproteins - metabolism; mutants; Mutation; nucleotide sequences; Plant Epidermis - cytology; Plant Epidermis - genetics; Plant Epidermis - metabolism; Plant physiology and development; Plant Proteins; Plant Roots - genetics; Plant Roots - metabolism; Plant Roots - ultrastructure; Plants, Genetically Modified; recombinant fusion proteins; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; reporter genes; root; root growth; root hairs; root tips; roots; signal transduction; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2004.02104.x

In the Arabidopsis root, patterning of the epidermal cell types is position-dependent. The epidermal cell pattern arises early during root development, and can be visualized using reporter genes driven by the GLABRA (GL)2 promoter as markers. The GL2 gene is preferentially expressed in the differentiating hairless cells (atrichoblasts) during a period in which epidermal cell identity is believed to be established. We show that AtAGP30 is also expressed in atrichoblasts. This gene encodes an arabinogalactan-protein (AGP) that is known to play a role in root regeneration and increases abscisic acid (ABA)-response rates. Although the expression level of this gene is regulated by the plant growth factors ABA and ethylene, only ABA was found to affect the tissue-specific pattern of expression. ABA also disrupts the expression pattern of the GL2::GUS (β-glucuronidase) reporter gene. Our results indicate that ABA regulates epidermal cell-type-specific gene expression in the meristematic zone of the Arabidopsis root, while ethylene is known to act at later stages of epidermal differentiation. Despite its effects on the early stages of root epidermal patterning, ABA does not affect root hair formation on mature wild-type epidermal cells, suggesting that other developmental cues, like positional information, can progressively over-ride the ABA-mediated disruption of early epidermal patterning.