Immunolocalization of β- D -glucans, pectins, and arabinogalactan-proteins during intrusive growth and elongation of nonarticulated laticifers in Asclepias speciosa Torr.

Abstract

Nonarticulated laticifers are latex-containing cells that elongate indefinitely and grow intrusively between the walls of meristematic cells. To identify biochemical mechanisms involved in the growth of nonarticulated laticifers, we have analyzed the distribution of various polysaccharides and proteoglycans in walls of meristematic cells in contact with laticifers, nonadjacent to laticifers, and in laticifer walls. In the shoot apex of Asclepias speciosa, the levels of callose and a (1-->4)-beta-galactan epitope are lower in meristematic walls in contact with laticifers than in nonadjacent walls. In contrast, we did not detect a decline in xyloglucan, homogalacturonan, and arabinogalactan-protein epitopes upon contact of meristematic cells with laticifers. Laticifer elongation is also associated with the development of a homogalacturonan-rich middle lamella between laticifers and their neighboring cells. Furthermore, laticifers lay down walls that differ from those of their surrounding cells. This is particularly evident for epitopes in rhamnogalacturonan I. A (1-->5)-alpha-arabinan epitope in this pectin is more abundant in laticifers than meristematic cells, while the opposite is observed for a (1-->4)-beta-galactan epitope. Also, different cell wall components exhibit distinct distribution patterns within laticifer walls. The (1-->5)-alpha-arabinan epitope is distributed throughout the laticifer walls while certain homogalacturonan and arabinogalactan-protein epitopes are preferentially located in particular regions of laticifer walls. Taken together, our results indicate that laticifer penetration causes changes in the walls of meristematic cells and that there are differences in wall composition within laticifer walls and between laticifers and their surrounding cells.

Intrusive growth of sclerenchyma fibers

“…Judging from our data obtained by flax stem staining with aniline blue, the dye revealing callose, fiber intrusive growth does not induce the synthesis of this polysac charide. Similar results were obtained at investigation of the cell walls of intrusively growing laticifers of showy milkweed [38]. Thus, callose absence during intrusive growth indicates that this process does not induce the wound response.…”

“…In the stem apex of showy milkweed (Asclepias speciosa Torr. ), a difference between binding of JIM5 antibody recognizing homogalacturonans with a low degree of methylation and JIM7 antibody against homogalacturonans with a high degree of methylation was more pronounced in the cell walls of intrusively growing nonarticulated laticifers than in the cell walls of surrounding cells [38].…”

Polyphenoloxidase Silencing Affects Latex Coagulation in Taraxacum Species

“…]) are organized in a branching system originating from a single precursor cell in the embryo that divides rapidly and spreads invasively during development. These are multinucleate cells that tend not to fuse into vessels (Serpe et al, 2002).…”

Micromorphology and Histochemistry of the Laticifers from Vegetative Organs of Asclepiadoideae species (Apocynaceae)

“…Cuando un órgano es cortado, hay una disminución de la presión de turgor en los laticíferos y el agua de los tejidos adyacentes atraviesa la pared contribuyendo para la exudación del látex (Downton, 1981;Pickard, 2008), generando una exudación más profusa que en Convolvulaceae. Serpe et al, (2001) y Serpe et al, (2002) investigaron imunocito químicamente las paredes de los laticíferos de Asclepias speciosa con relación a la presencia de sustancias que las diferencien de las paredes de las demás células; calosa, lignina y compuestos fenólicos no fueron encontrados, pero ellos constataron que la porción madura de los laticíferos tiene propiedades citoquímicas diferentes de las paredes de la porción más joven con relación a epitopos de pectina y que los diferentes componentes de la pared exhiben patrón de distribución distinta. Estas mismas características se observaron en el análisis histoquímico de las paredes de los laticíferos en el presente estudio y también fueron observadas durante el desarrollo de los laticíferos en especies de cerrado (Demarco et al, 2006).…”

“…La composición, el arreglo de las moléculas y el metabolismo de la pared celular están relacionados a las características del crecimiento de una célula vegetal (Carpita y McCann, 2000) y, aunque haya discordancia con relación al modo de crecimiento de los laticíferos en las especies de esta familia (Demarco et al, 2006), poco se sabe sobre sus paredes (Serpe et al, 2001;Serpe et al, 2002;Demarco et al, 2006).…”