Dr. Roberts et Cw. Mims, ULTRASTRUCTURE OF EXTRACELLULAR-MATRIX DEPOSITS ASSOCIATED WITH CONIDIA OF THE POWDERY MILDEW FUNGUS BLUMERIA-GRAMINIS F SP. HORDEI, International journal of plant sciences, 159(4), 1998, pp. 575-580
Small pieces of sterile dialysis membrane were touched to sporulating
colonies of the powdery mildew fungus Blumeria graminis f. sp. hordei
and either cryofixed within 5 s or incubated for 30 min or 2 h before
cryofixation. Following freeze substitution and processing for study w
ith transmission electron microscopy, thin sections of conidia on dial
ysis membrane were examined ultrastructurally. Each conidium was surro
unded by a copious deposit of an extracellular matrix (ECM) material.
ECM deposits developed as soon as conidia contacted membranes and pers
isted for the duration of the 2-h time period of this study. While onl
y a thin layer of ECM was present between the central portion of the u
nderside of each conidium and the underlying membrane, ECM filled the
space between the curved conidium surface and the membrane and extende
d halfway or more up the surface of the conidium. The ECM spread out a
way from the conidium onto the membrane for a distance of up to 30 mu
m. Strands of ECM also extended up over some conidia. Most conidia wer
e not in direct contact with their respective ECM deposits, and some w
ere displaced totally from their deposits, which adhered closely to me
mbranes. The Thiery stain for polysaccharides gave little if any stain
ing of the ECM. Gold labeling for mannose residues in the matrix using
Conconavilin A was negative.