Light microscopy and transmission electron micrographs of the <i>in planta</i> cellular phenotype of <i>E</i>. <i>festucae</i> WT and <i>gpiB</i>, <i>sspM</i>, <i>sspN</i> and <i>sspO</i> deletion mutant strains.

(A) Light microscope analysis of fixed L. perenne pseudostem cross sections stained with Toluidine blue. The focus of the section is on the vascular bundles and surrounding regions; Bar = 10 μm. (B) TEM analysis of hyphal growth in the host apoplast; Bar = 2 μm. (C) Magnified transmission electron micrograph of one single hypha; Bar = 1 μm. Representative images from one of the independent mutants for each gene. Red arrows indicate position of hyphae and green arrows epiphyllous hyphae.