Nucleic acid changes during germination and axenic development of flax rust ( Melampsora lini)

Abstract

The nucleic acid extracts of the various growth stages of M. lini all possessed DNA, ribosomal RNA and soluble RNA but the proportions were far from constant. Ground, ungerminated uredospores had a high ribosomal RNA level and a consequent low DNA/RNA ratio, Germination, or even preliminary hydration prior to germination, initiated a degradation of ribosomal RNA with a marked decrease in acid-precipitable RNA. This appeared to be a valid consequence of germination, and not an extraction artifact. The DNA levels were not markedly changed over the first 12 h of germination. The nucleic acids from young axenic colonies resembled those from germinated spores, both quantitatively and qualitatively. Levels of RNA were less than half those present in the saprophytic fungi with which they were compared. The total nucleic acid content of older stromatal masses was very low, with an apparently high level of DNA. The extractable nucleic acid had a DNA/RNA ratio very similar to that of the young colonies, although there was an increased complement of low molecular weight RNA in the old colonies.