Differentiation of xylem cells in rolC transgenic aspen trees - a study of secondary cell wall development

Xylem cell differentiation of 35S-rolC transgenic aspen was analyzed and compared with wild type trees. The transgenic trees, mainly characterized by dwarfism and physiological alterations, did not show distinctive differences in the structure and chemical composition of xylem cell walls as compared with the wild type trees. However, there was a difference in the dynamics of differentiation. In the transgenics the formation of xylem cells was delayed and the differentiation zone reduced to a few rows. PATAg and KMnO4 staining in electron microscopy as well as UV-microspectrophotometry revealed that in the transgenics during secondary wall formation polysaccharides and lignin were simultaneously deposited close to the cambium. Immunocytochemical techniques have visualized the first deposition of condensed lignin in cell corners and of non-condensed lignin in secondary walls near cell corners. Because of altered formation and differentiation of xylem cells, 35S-rolC transgenic aspen may be useful to study factors controlling the differentiation continuum.