Immunocytochemical Localization of Cell Wall-Bound Thionins and Hydroxyproline-Rich Glycoproteins in Fusarium culmorum-Infected Wheat Spikes

In the present study, a rabbit polyclonal antiserum against cell wall‐bound thionins from barley leaf and a mouse monoclonal antibody against hydroxyproline‐rich glycoproteins (HRGP) from maize were used to investigate the subcellular localization of thionins and HRGP or extensins in Fusarium culmorum‐infected wheat spikes by means of the immunogold labelling technique. The proteins were localized in cell walls of different tissues including the lemma, ovary and rachis, while the cytoplasm and organelles in these tissues showed almost no labelling. However, accumulation of thionins and HRGP in infected wheat spikes of resistant wheat cultivars differed distinctly from those of susceptible cultivars. Compared with the healthy tissues, labelling densities for the two types of proteins in cell walls of the infected lemma, ovary and rachis increased only slightly in the susceptible cultivar Agent, while in cell walls of infected tissues of the resistant cultivar Arina labelling densities of thionins and HRGP increased markedly. These findings indicated that accumulation of thionins and HRGP in cell walls of infected resistant wheat spikes may be involved in defence responses to infection and in spreading of F. culmorum.