The physiology of host–parasite relations. XIX. Further observations on nucleoprotein changes in wheat leaf nuclei during rust infection

Abstract

Cytophotometric measurements of DNA (Feulgen) and protein-bound lysine and arginine (fluorodinitrobenzene-Sakaguchi) were made on nuclei in mesophyll cells of infected and uninfected leaves of Little Club wheat at intervals of 2 to 4 days up to 13 days after inoculation with uredospores of race 15B of the stem rust fungus (Puccinia graminis tritici Erikss. and Henn.). No change in host DNA was found within 6 days after inoculation, but there were marked decreases in protein-bound lysine and arginine as early as 2 days after inoculation. The DNA/lysine and DNA/arginine ratios were higher in rust-affected host nuclei, but infection did not alter the ratio of protein-bound lysine to arginine. In another series of measurements it was shown that rust infection caused striking increases in the volume and the RNA and protein contents of host nucleoli. These changes persisted even in advanced infections.All the results are consistent with our earlier observations and indicate that profound changes in nuclear metabolism are induced by infection with the rust fungus.