The Stimulatory Effect of Light on Nucleic Acid Synthesis in the Mould Blastocladiella emersonii

Abstract

The fungus Blastocladiella emersonii possesses neither chlorophyll nor colored carotenoids; yet, visible light induces increased nuclear multiplication, increased synthesis of DNA relative of total nucleic acid, and detectable changes in the soluble phosphorus pool of the fungus. The stimulatory effect is detectable through ontogeny, from the 1st few hours after germination to the end of the generation time of c. 15 to 25 hr. (depending on temperature). Light could be replaced by providing the plants with thymidine or thymine, but not with the corresponding RNA base, uracil. The DNA of B. emersonii contained the 4 principal bases usually associated with this nucleic acid. Finally, the interrelationships between DNA and RNA, and the effects thereon of nucleic acid analogues and inhibitors, were studied also. In particular, it was found that the DNA per cell doubled just before the 1st mitosis, while the total nucleic acid concentration did not change. The results of the later experiments were interpreted in terms of the transformations which occur in the RNA-rich nuclear cap in the spores of the fungus during germination.