Metabolism of alicyclic acids and phenylpropanoids by uredospores of wheat stem rust and wheat leaf rust

Abstract

Uredospores of wheat leaf rust did not take up or metabolize exogenous supplies of quinate-U-14C, shikimate-U-14C, p-coumarate-α-14C, or ferulate-α-14C. Caffeate-α-14C was converted to an unidentified ether-insoluble component which was recovered from the germination medium.Phenylalanine-U-14C and tyrosine-U-14C were readily taken up by uredospores of both rusts and were recovered from the solvent-soluble and insoluble fractions. No evidence for phenylalanine/tyrosine interconversion was obtained. Radioactivity was not incorporated into glycosides or free and bound esters of phenolic acids when phenylalanine-U-14C or tyrosine-U-14C were used as precursors. Radioactivity was not detected in free phenolic acids when uredospores were fed phenylalanine-U-14C. When tyrosine-U-14C was the precursor, radioactive p-coumarate was detected in the germination medium kept at 20 °C, and radioactive p-coumarate and caffeate were both recovered from the germination medium kept at 30 °C.Extracts of uredospores of wheat stem rust and wheat leaf rust contained shikimate dehydrogenase and tyrosine ammonia-lyase. Quinate dehydrogenase and phenylalanine ammonia-lyase were not detected.