Extracellular matrix, esterase and the phytotoxin prehelminthosporol in infection of barley leaves by Bipolaris sorokiniana

Light microscopy and cryo-scanning electron microscopy showed that hyphae of Bipolaris sorokiniana adhered to the wax surfaces of barley leaves by means of an extensive extracellular matrix (ECM). Prehelminthosporol, the major non-host specific phytotoxin formed by B. sorokiniana was immunolocalized in large amounts in the ECM surrounding the hyphae. Similarly, esterase activity involved in degradation of the cuticular wax surface was found in the ECM. Therefore, it appears that the ECM is not only important for adhesion of the fungus to its host, but also functions as a sink of phytotoxins and lytic enzymes important for infection of the host plant.