Side chains of pectic polysaccharides are regulated in relation to cell proliferation and cell differentiation
Article first published online: 5 JAN 2002
The Plant Journal
Volume 20, Issue 6, pages 619–628, December 1999
How to Cite
Willats, W. G. T., Steele-King, C. G., Marcus, S. E. and Knox, J. P. (1999), Side chains of pectic polysaccharides are regulated in relation to cell proliferation and cell differentiation. The Plant Journal, 20: 619–628. doi: 10.1046/j.1365-313X.1999.00629.x
- Issue published online: 5 JAN 2002
- Article first published online: 5 JAN 2002
- Received 4 August 1999; revised 23 September 1999; accepted 21 October 1999.
The occurrence and function of the side chains occurring in the rhamnogalacturonan I domain of pectic poly- saccharides have been investigated during carrot cell development using monoclonal antibodies to defined epitopes of (14)-β-D-galactan and (15)-α-L-arabinan. Immunolocalization studies of carrot root apices indicated that cell walls in the central region of the meristem contained higher levels of (15)-α-arabinan than the cell walls of surrounding cells. In contrast (14)-β-galactan was absent from the cell walls of the central meristematic cells but appeared abundantly at a certain point during root cap cell differentiation and also appeared in cell walls of differentiating stele and cortical cells. This developmental pattern of epitope occurrence was also reflected in a suspension-cultured carrot cell line that can be induced to switch from proliferation to elongation by altered culture conditions. (14)-β-galactan occurred at a low level in cell walls of proliferating cells but accumulated rapidly in cell walls following induction, before any visible cell elongation, while (15)-α-arabinan was present in cell walls of proliferating cells but was absent from cell walls of elongated cells. Immunochemical assays of the cultured cells confirmed the early appearance of (14)-β-galactan during the switch from cell proliferation to cell elongation. Anion-exchange chromatography confirmed that (14)-β-galactan was attached to acidic pectic domains and also indicated that it was separate from a distinct homogalacturonan-rich component. These results indicate that the neutral components of pectic polysaccharides may have important roles in plant cell development.