Septal Pores in the Heterobasidiomycetidae, Puccinia Graminis and P. Recondita

Abstract

The septal pores in uredial mycelium of Puccinia graminis and P. recondita lack the septal swelling and septal pore cap (dolipore‐parenthosome configuration) typically associated with the pores of previously investigated Homobasidiomycetidae and the Tremellales among the Heterobasidiomycetidae. The pores in young hyphae of these two species of Puccinia are characterized by the presence of a cytoplasmic matrix which apparently occludes the pore and acts as a plug, thus preventing the migration of organelles from cell to cell. Large vesicles are typically present at the periphery of the pore matrix and the matrix may be very incompletely bounded by a membrane. Nuclei and other cytoplasmic structures migrate from cell to cell through an opening in the septum lateral to the pore. The available evidence indicates that this peripheral gap in the septum results from a breakdown of a portion of an initially complete septum rather than from incomplete septum formation. In addition to the centripetally formed septa, the hyphae of P. graminis and P. recondita are further compartmentalized by shallow infoldings of the lateral wall and limited unilateral septum formation. There is apparent free passage of cellular material between adjacent compartments.

Ultrastructural Observations on the Septal Pore inCronartium Flaccidum(Alb. Et Schw.) Wint. Also in Relation to the Taxonomy of the Uredinales

“…The occurrence of similar organelles more or less associated with the pore and the septum of the other Uredinales has been reported by several authors (EHRLICH et al 1968;CoFFEY et al 1972;LITTLEFIELD and BRACKER 1971;}ONES 1973;ROBB et al 1973;HEATH and HEATH 1975;WALLES 1974). As regard their morphology, according to the literature concerning rust microbodies (see references in LITTLEFIELD and HEATH 1979), the microbody paracristal inclusions seen by the author in the mycelium of C. flaccidum is a characteristic feature of the microbodies found in the proximity of the septum and pore of the vegetative mycelium hyphae.…”

“…The cytoplasmic area next to the pore, devoid of other organelles but usually containing microbodies, is the most salient ultrastructural peculiarity of many Uredinales (EHRLICH et al 1968;CoFFEY et al 1972;RoBB et al 1973;HEATH and HEATH 1975;WALLES 1974). In the dikaryotic mycelium of Puccinia graminis Pers.…”

“…(CoFFEY et al 1972), in contrast to what has been observed in the monokaryotic mycelium of Cronartium ribicola J. C. Fischer (ROBB et al 197 3) and in the monokaryotic and dikaryotic mycelium of C. flaccidum this cytoplasmic area appears to be surrounded, at least partially, by a membrane. This structural characteristic, according to EHRLICH et al ( 1968 ), could be regarded as one of the morphological aspects which make the pore of the Uredinales resemble the complex structure of the dolipore. Therefore, according to these authors, the function of such cytoplasmic area is to plug the pore preventing the intercellular migration of nuclei and of other cytoplasmic organelles in the hypha; in the higher Basidiomycetes this action, in order to maintain the functional diploidy, is performed by the dolipore (MooRE and McALEAR 1962;MooRE 1965).…”

“…Therefore, according to these authors, the function of such cytoplasmic area is to plug the pore preventing the intercellular migration of nuclei and of other cytoplasmic organelles in the hypha; in the higher Basidiomycetes this action, in order to maintain the functional diploidy, is performed by the dolipore (MooRE and McALEAR 1962;MooRE 1965). On the grounds of this hypothesis, namely the functional analogy between the septal pore apparatus of the rusts and the dolipore-septum of the higher Basidiomycetes (EHRLICH et al 1968), LITTLE-FIELD and HEATH ( 1979) suggest that these two types of equally complex septum pore apparata have presumably followed two independent phylogenetic lines of evolution.…”

“…Researches on the ultrastructure of the septal pore of the Uredinales showed that, although they are Phragmobasidiomycetes, their septa and pores are similar to those typical of the Ascomycetes (EHRLICH and EHRLICH 1963;MOORE 1965;EHRLICH et al 1968;LoNGO and NALDINI 1970;LITTLEFIELD and BRACKER 1971;CoFFEY et al 1972;}ONES 1973). In these early studies, the observations made by some authors (GIEsY and DAY 1965;}ERSILD et al 1967) concerning a few Holobasidiomycetes were extensively discussed.…”