Wall ingrowths in epidermal transfer cells of Vicia faba cotyledons are modified primary walls marked by localized accumulations of arabinogalactan proteins

• Published in: Plant and cell physiology Vol. 48; no. 1; pp. 159 - 168
• Main Authors: Vaughn, K.C.(USDA, Agricultural Research Service, Stoneville, MS (USA). Southern Weed Science Research Unit), Talbot, M.J, Offler, C.E, McCurdy, D.W
• Format: Journal Article
• Language: English
• Published: Japan Oxford University Press 01.01.2007; Oxford Publishing Limited (England)
• Subjects: Biological Transport; Cell Wall - physiology; Cell Wall - ultrastructure; CELL WALLS; Cotyledon - physiology; Cotyledon - ultrastructure; Glucans - metabolism; Immunohistochemistry; IMMUNOLOGIE; IMMUNOLOGY; INMUNOLOGIA; MORFOGENESIS; MORPHOGENESE; MORPHOGENESIS; Mucoproteins - metabolism; PARED CELULAR; PAROI CELLULAIRE; Pectins - metabolism; Plant Proteins - metabolism; PROTEOGLICANOS; PROTEOGLYCANE; PROTEOGLYCANS; VICIA FABA; Vicia faba - physiology; Xylans - metabolism; Wall ingrowths; Arabinogalactan proteins; Transfer cells; Immunocytochemistry; Cell wall
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/pcp/pcl047

Despite the importance of transfer cells in enhancing nutrient transport in plants, little is known about how deposition of the complex morphology of their wall ingrowths is regulated. We probed thin sections of mature cotyledon epidermal transfer cells of Vicia faba with affinity probes and antibodies specific to polysaccharides and glycoproteins, to determine the distribution of these components in their walls. Walls of these transfer cells consist of the pre-existing primary wall, a uniformly deposited wall layer and wall ingrowths which are comprised of two regions; an electronopaque inner region and an electron-translucent outer region. The primary wall reacted strongly with antibodies against esterified pectin, xyloglucan, the side chains of rhamnogalaturonan-1 and a cellulase-gold affinity probe. The electronopaque inner region of wall ingrowths displayed a similar labeling pattern to that of the primary wall, showing strong cross-reactivity with all antibodies tested, except those reacting against highly de-esterified pectins. The electronopaque outer layer of developmentally more mature wall ingrowths reacted strongly with anti-callose monoclonal and polyclonal antibodies, but showed no reaction for pectin or xyloglucan antibodies or the cellulase-gold affinity probe. The plasma membrane-wall interface was labeled strongly with anti-arabinogalactan protein (AGP) antibodies, with some AGP-reactive antibodies also labeling the electrontranslucent zone. Nascent wall ingrowths were labeled specifically with AGPs but not anti-callose. A reduction in wall ingrowth density was observed when developing transfer cells were exposed to beta-D-glucosyl Yariv reagent compared with controls. Our results indicate that wall ingrowths of transfer cells are primary wall-like in composition and probably require AGPs for localized deposition.