Folate derivatives in ungerminated and germinated uredospores of wheat stem rust

Abstract

Extracts of ungerminated uredospores and of uredospores germinated for 6 h and 12 h were assayed for folates with Lactobacillus casei, Streptococcus faecalis, and Pediococcus cerevisiae. These organisms did not respond to the extracts without conjugase treatment, indicating that most of the folates were present in conjugated form with more than three glutamic acid moieties per molecule. During the 6-h and 12-h germination periods the content of growth factors for L. casei declined to 70.9% and 46.0% of initial levels. In this same period, the content of growth factors for S. faecalis declined to 54.5% and 15.2% of initial levels, indicating an increase in the proportion of methylated folates during uredospore germination.This trend was confirmed in a detailed analysis of folate components after fractionation of the extracts on DEAE-cellulose columns. The folate profiles consisted of five peaks. Two peak fractions present in profiles from ungerminated spores contained mostly formylated folates and were greatly reduced or absent in profiles from germinated spores. A peak fraction composed of a 5-methyl-tetrahydrofolate conjugate was not observed in profiles of ungerminated spores but was predominant in those from spores germinated for 12 h.