RESUMEN
Although cell wall remodeling is an essential feature of plant growth and development, the underlying molecular mechanisms are poorly understood. This work describes the characterization of Arabidopsis (Arabidopsis thaliana) plants with altered expression of ARAF1, a bifunctional alpha-L-arabinofuranosidase/beta-D-xylosidase (At3g10740) belonging to family 51 glycosyl-hydrolases. ARAF1 was localized in several cell types in the vascular system of roots and stems, including xylem vessels and parenchyma cells surrounding the vessels, the cambium, and the phloem. araf1 T-DNA insertional mutants showed no visible phenotype, whereas transgenic plants that overexpressed ARAF1 exhibited a delay in inflorescence emergence and altered stem architecture. Although global monosaccharide analysis indicated only slight differences in cell wall composition in both mutant and overexpressing lines, immunolocalization experiments using anti-arabinan (LM6) and anti-xylan (LM10) antibodies indicated cell type-specific alterations in cell wall structure. In araf1 mutants, an increase in LM6 signal intensity was observed in the phloem, cambium, and xylem parenchyma in stems and roots, largely coinciding with ARAF1 expression sites. The ectopic overexpression of ARAF1 resulted in an increase in LM10 labeling in the secondary walls of interfascicular fibers and xylem vessels. The combined ARAF1 gene expression and immunolocalization studies suggest that arabinan-containing pectins are potential in vivo substrates of ARAF1 in Arabidopsis.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimología , Pared Celular/metabolismo , Polisacáridos/metabolismo , Xilosidasas/metabolismo , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , ADN Bacteriano , Expresión Génica , Perfilación de la Expresión Génica , Glucuronidasa/metabolismo , Inmunohistoquímica , Monosacáridos/metabolismo , Mutagénesis Insercional , Análisis de Secuencia por Matrices de Oligonucleótidos , Fenotipo , Tallos de la Planta/crecimiento & desarrolloRESUMEN
Glycosyl hydrolases are important mediators of plant cell wall modification during plant development. These enzymes catalyse the hydrolytic release of specific sugars, such as L-arabinose, from the polysaccharide-rich cell wall matrix. The cloning and expression analysis of two genes, AtASD1 and AtASD2, encoding putative alpha-L-arabinofuranosidases in Arabidopsis thaliana are reported here. AtASD1 and AtASD2 identities were assigned on the basis of homology to plant and microbial family 51 glycoside hydrolases. Using RT-PCR, RNA gel blot analysis and reporter gene expression analysis, AtASD1 and AtASD2 were shown to have different developmental expression profiles. High levels of AtASD1 promoter activity are present in multiple tissues during vegetative and reproductive growth. AtASD1 expression is particularly intense in zones of cell proliferation, the vascular system, developing and regressing floral tissues, and floral abscission zones. By comparison, AtASD2 expression is limited to the vasculature of older root tissue and to some floral organs and floral abscission zones.