Abnormalities in the hyphal distribution and ultrastructure of <i>ΔsidN</i> mutants in perennial ryegrass plants.

<p>A. Light micrographs of 1 µM cross sections of the inner leaf sheath of perennial ryegrass infected with wild-type <i>E. festucae</i> Fl1 (WT) and <i>ΔsidN</i> mutant 85 (85) are shown. The top panel is a cross section of mesophyll cells, whereas the lower panel is a close up of vascular tissue. Representative hyphae are indicated by arrows and the circle on the 85 panel indicates epiphyllous hyphae. Inserts show higher magnification of the endophyte hyphae indicated by the arrowheads in the main panels. Bars = 20 µM. B. Transmission electron micrographs of cross sections of endophyte hyphae in the intercellular spaces of perennial ryegrass. Wild-type <i>E. festucae</i> Fl1 (WT), complemented <i>ΔsidN</i> strain (C-<i>sidN</i>) <i>ΔsidN</i> mutant 54 (54), <i>ΔsidN</i> mutant 85 (85) are shown. Samples shown were photographed from leaf sheath sections, with WT, C-<i>sidN</i>, and <i>ΔsidN</i> 85 hyphae located in mesophyll tissue, whereas <i>ΔsidN</i> 54 is in sclerenchma tissue. c, cytoplasm, v, vacuole. Bars = 500 nm.