High-affinity binding of fungal β-glucan elicitors to cell membranes of species of the plant family Fabaceae

✍ Scribed by Eric G. Cosio; Markus Feger; Connie J. Miller; Luis Antelo; Jürgen Ebel

• Publisher: Springer-Verlag
• Year: 1996
• Tongue: English
• Weight: 882 KB
• Volume: 200
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00196654

✦ Synopsis

Microsomal preparations of six species of the plant family Fabaceae were screened for high-affinity binding of branched (1 ~ 3), (1 --, 6)-[3-glucans. Oligoglucosides of this type are specific elicitors of phytoalexin accumulation in soybean (Glycine max L.), a member of this family. The species studied were alfalfa (Medicago sativa L.), broadbean (Vicia faba L.), chickpea (Cicer arietinum L.), french bean (Phaseolus vulgaris L.), pea (Pisum sativum L.), and white lupin (Lupinus albus L.). A 125I-labeled 4-(2-aminophenyl)ethylamine conjugate of a (1 ~ 3), (1 ~ 6)-[3-glucan fraction with an average degree of polymerization (DP) of 18, obtained from mycelial walls of Phytophthora sojae, was used as radioligand for initial screening. The structural complexity of this fraction allowed the identification of binding sites with affinities for isomeric structures other than the (1 ~ 3), (1--* 6)hepta-[3-glucoside for which soybean binding sites display highest affinity. Radioligand competition experiments against unlabeled fungal [3-glucan resulted in the identification of high-affinity binding in alfalfa, bean, lupin, and pea. Half-maximal competition concentrations (ICso) for fungal [3-glucan in these species were between 5 and 30 nM. Pseudoheterologous radioligand competition by unlabeled hepta-[3-glucoside showed that for alfalfa, lupin and pea the ICs0 values for this structure (4 to 16 nM)