Indole‐3‐methylglucosinolate biosynthesis and metabolism in clubroot diseased plants

Abstract

lndole‐3‐methylglucosinolate biosynthesis and metabolism in roots of Brassica napus (swede, cv. Danestone II) infected with Plasmodiophora brassicae Wor. were investigated with a pulse feeding technique developed to infiltrate intact tissue segments with labelled substrates. Infected root tissue metabolized [ 14 C]‐L‐tryptophan to indole‐3‐methylglucosinolate, indole‐3‐acetonitrile, and some other lipophilic indole compounds. The incorporation of radioactivity into these compounds was significantly enhanced in infected tissue compared with control tissue. A time course study showed a high turnover of indole‐3‐methylglucosinolate and indole‐3‐acetonitrile in infected tissue. However, thioglucoside glucohydrolase activity was not changed in infected tissue compared with control tissue. Disc electrophoresis revealed the same isoenzyme in both tissues. Control and infected tissues both rapidly hydrolyzed [ 14 C]‐indole‐3‐acetonitrile in vivo. The possibility of a disease specific biosynthesis of indole‐3‐acetic acid from indole‐3‐methylglucosinolate as the result of a changed compartmentation is discussed.