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

Abstract

-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 KMnO 4 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.Populus / rolC / wood formation / lignification / electron microscopy / immunogoldlabelling / UV-microspectrophotometry Résumé -Différenciation des cellules du xylème chez le peuplier transgénique 35S-rolC -une étude de la formation des parois secondaires. La différenciation des cellules du xylème du peuplier transgénique 35S-rolC a été analysée et comparée à celle du peuplier non transformé. Les arbres transgéniques nains, qui se caractérisent par des altérations physiologiques et morphologiques ne présentaient pas de différences dans leur architecture ni dans la composition des parois des cellules du xylème par comparaison avec les plantes normales. En revanche, on a pu observer une différence dans la dynamique de la différenciation. Dans les arbres transgéniques, la formation des cellules du xylème est retardée et la zone de différenciation est réduite à quelques rangées de cellules. De ce fait, la formation et la lignification de la paroi secondaire ont pu être observées dans des cellules moins développées que dans le peuplier normal ainsi que cela a été mis en évidence par microspectrophotométrie-UV et par les contrastants PATAg et KMnO 4 en microscopie électronique à transmission. Des analyses immunocytochimiques ont révélé la toute première déposition de lignines condensées dans les jonctions intercellulaires et de lignines non condensées dans les parois secondaires adjacentes aux triangles de jonctions. Ces altérations dans la formation et la différenciation des cellules du xylème font du peuplier transgénique 35S-rolC un matériel utile pour l'étude des facteurs contrôlant le continuum de différenciation.Populus / rolC / formation des cellules du xylème / lignification / microscopie électronique à transmission / immunocytochimie / microspectrophotométrie-UV

Seasonal dynamics of wood formation in Oriental beech (Fagus orientalis Lipsky) along an altitudinal gradient in the Hyrcanian forest, Iran

“…The onset of lignification was observed almost 10 days after secondary wall thickening, starting in the vessel elements (Marion et al 2007;Grünwald et al 2002). To justify the higher lignification of vessels than fibers in oak, Yoshinaga et al (1992) proposed that vessel cell walls must withstand large transversal tension forces resulting from the transpiration stream in plants.…”

Stability of transgene expression in poplar: A model forest tree species

“…However, the future utilisation of transgenic trees on a commercial basis will depend upon a thorough evaluation of the environmental risks, modified phenotypes and transgene stability over extended time periods [12]. In this paper we have addressed the stability aspects by following transgene expression in in vitro-, greenhouse-and field-grown poplar, which has become a model forest tree species [6,17]. Since for most biotechnological uses, the transgenes will need to be regulated by inducible or tissue-specific promoters, so as to control both the location and the time of expression in the plant [15,45,49], we decided to evaluate the expression stability of the uidA reporter gene under the control of both a tissue-specific promoter (EuCAD) and a constitutive promoter (35S).…”

Topochemical investigations of cell walls in developing xylem of beech (Fagus sylvatica L.)

“…Cell wall thickening and lignification have already been studied from different points of view: (1) lignin distribution within annual growth rings (Fukazawa and Imagawa 1981;Takabe et al 1992), (2) studies of heterogeneous cellular distribution of guaiacyl and syringyl lignins (Fergus and Goring 1970a;Yoshinaga et al 1997;Ruel et al 1999;Terashima 2000), and (3) lignification dynamics of different cell types (Nakashima et al 1997;Grü nwald et al 2002;Grič ar et al 2005). Numerous methods, such as microautoradiography, histochemistry, interference microscopy, fluorescence microscopy, transmission electron microscopy (TEM), and cellular UV-microspectrophotometry (UMSP), have been used to reveal structural and chemical details (e.g., Murmanis and Sachs 1969;Terashima and Fukushima 1989;Donaldson et al 1999;Donaldson 2001;Koch and Kleist 2001;Schmitt and Melcher 2003;Koch and Grü nwald 2004;Grič ar et al 2006Grič ar et al , 2007a.…”

“…Yoshinaga et al (1997) investigated the stages of lignification in oak xylem by measuring cell wall thickness and UVabsorbance values in relation to the distance from the cambial zone. Grü nwald et al (2002) applied the same method to compare cell differentiation and lignification in wild and transgenic aspen trees. Dü nisch et al (2003) investigated the kinetics of cell differentiation in Swietenia macrophylla with high resolution laser measurements, in situ, following cell enlargement and cell differentiation at very short time intervals, showing how fast the individual cells were formed.…”