G. B. Ouellette

Use of pectinases complexed to colloidal gold for the ultrastructural localization of polygalacturonic acids in the cell walls of the fungus Ascocalyx abietina.

SummaryThree pectinase—gold complexes were used to localize polygalacturonic acids in the fungusAscocalyx abietina (Lagerberg) Schlaepfer-Bernhard. With the pectinesterase and pectin lyase—gold complexes, the labelling was uniformly distributed over the fungus walls and did not seem to be significantly influenced by the tissue preparation. With the polygalacturonase—gold complex, differences in the labelling distribution were noted according to the fixation procedure indicating, therefore, that osmication of the tissues could greatly interfere with the localization of the specific enzyme binding sites. These results demonstrate, for the first time, the possibility of detecting polygalacturonic acids by means of different gold-complexed pectinases.

Ultrastructure of the alveolar network and its relation to coating on vessel walls in elms infected by Ophiostoma novo-ulmi and in other plants affected with similar wilt diseases

En olmos afectados por la grafiosis, la red alveolar, demarcada por bandas filamentosas, y confluente con acumulaciones de la misma sustancia (cubricion) presentes en las paredes de los vasos, aparece regularmente en los elementos conductores. Sustancias similares tapizan las paredes de los vasos en secciones de madera delgada de olmo inoculada y esterilizada, y posteriormente criofijadas a altas presiones. Se observo que la cubricion se conecta con las celulas del micelio y que ocasionalmente contenia pequenas particulas opacas del tamano de los ribosomas, estructuras membranosas y vesiculares, asi como que, tras la incubacion de astillas lenosas cogidas de muestras enfermas incubadas en agar, aun se presentaba una sustancia similar. La cubricion y las bandas alveolares aumentaron su espesor en la confluencia con otras bandas o estructuras membranosas. Estructuras y sustancias similares aparecieron tambien en otras plantas afectadas por enfermedades similares originadas por hongos que producen marchitamiento. En todos los sistemas, la cubricion compacta no pudo ser marcada como quitina, celulosa ni pectina. En zumaque (Rhus typhina), la sonda de ADN se pego a la cubricion. En resumen, a la vista de estos datos, parece ser que la cubricion y la red alveolar no estan formados por componentes inertes, un hecho que indica su probable origen patogenico. Se sugiere que esos elementos podrian ser importantes no solo en las fases iniciales de la infeccion, sino tambien, en infecciones mas desarrolladas o recurrentes, en el momento en que los mecanismos de resistencia del hospedante no son efectivos.

A Review of Ultrastructural and Ultracytochemical Studies of Infection Processes in Some Plant Wilt Diseases: The Opaque Matter Extensively Involved, Its Links with Pathogen Elements, Insights into Its Nature

The present review is based on results of several years of investigation on the pathogenesis of plant wilt diseases using for one of the main aspects, several labeling techniques at the ultrastructural level: autoradiography with (3)H-thymidine; gold-tagged lectins, enzymes, polyclonal, and monoclonal antibodies. Thus, opaque matter (OM), labeling for DNA with the appropriate markers, can be abundant in and associated with host tissue reactions and pronounced alterations (particularly in newly differentiated xylem). The presence of structures (called P-elements) in OM, paralleled by a similar occurrence in nuclei of both the host and pathogen cells, is considered as being also indicative of a cytoplasmic nature for this OM and most likely originating from fungal elements.