Detection of galactose in two fungi causing wilt diseases and in their plant host tissues by means of gold-complexed Ricinus communis agglutinin I

Abstract

The Ricinus communis agglutinin I (RcA1) was bound to colloidal gold and used for the detection of galactose residues in two pathogenic fungi causing wilt diseases, and in their host tissues. In cells of Fusarium oxysporum f.sp. radicis-lycopersici Jarvis and Shoemaker (FORL), these sugar residues were abundantly present in the polysome-rich cytoplasmic regions but were absent in the walls. In cells of Ophiostoma ulmi (Buism.) Nannf., galactose residues were found in the cytoplasm; they were also present, although in small amounts, in the outer wall layers. In tomato root tissues invaded by FORL, the earliest response was characterized by the accumulation of vesicles within the paramural spaces. Numerous galactose residues were found to occur in such vesicles. Distribution of these residues within tomato root cell walls appeared to vary with the degree of tissue differentiation. Host cell penetration by FORL did not induce wall digestion as indicated by the absence of areas of lysis. In dead elm wood tissues colonized by O. ulmi, galactose residues were detected in the compound middle lamella of parenchyma cells and in the gelatinous S3 layer of fibres. When O. ulmi penetrated the host walls, several zones of lysis were present at the periphery of penetration channels.