Evidence for the presence of messenger ribonucleic acid in Allomyces macrogynus mitospores

Abstract

Sucrose density gradient analysis was used to show that polysomes were present in the mitospores ofAllomyces macrogynus. Fifty percent of the spore monosomes were shown to be resistant to dissociation by 0.8 M KCl, indicating that messenger ribonucleic acid (mRNA) was bound to them. These polysomes and all the spore ribosomes were contained in the nuclear cap. Only 4S RNA could be demonstrated in the extra-cap fraction. Hybridization studies using 3H-labeled polydeoxythymidylic acid indicated that polyadenylate was present to the extent of 0.08% of the total spore RNA. Sixty-eight percent of the polyadenylic acid is found in the nuclear cap, and 32% is found in the extra-cap fraction. It was demonstrated that [3H]uridine was taken up by the spores and converted to uridine triphosphate. Lack of incorporation of 3H into RNA indicated that the spores do not synthesize RNA. Thus, the mRNA found in spores is synthesized prior to spore formation.

Properties of polyadenylate-associated ribonucleic acid from Saccharomyces cerevisiae ascospores

“…What controls exist to prevent protein synthesis from occurring until germination is an open question. Our data, as well as the data of others (3,7,11,12,14,15,16,18,19,28,29,30,35), would argue that regulation must be at least partially at the level of translation. The observation that there is considerable poly(A)(+) RNA in yeast ascospores and that some of it is associated with polyribosomes suggests a number of molecular approaches to questions of maternal effects and to the persistence of information in RNA throughout the processes of meiosis and sporulation.…”

“…Gradient SDS-polyacrylamide slab gels (3 to 12% acrylamide; 0.11 to 0.3% BIS; 0.2% SDS) were prerun in 0.04 M sodium acetate-0.0001 M EDTA-0.02 M Tris (pH 7.5)-0.2% SDS at 100 V, constant current, for 30 min before the RNA samples were added. Final electrophoresis was at 100 V, constant current, for 3.5 to 4.0 h (or until a bromophenol blue dye marker reached the bottom of the slab).…”

Stored mRNA in sporangiospores of the fungus Mucor racemosus

“…Several other fungal species, including Allomyces macrogynus (20), Botryodiplodia theobromae (6), Blastocladiella emersonii (5), and Rhizopus stolonifer (4,23), produce dormant spores containing stored mRNA which is translated upon germination. The presence of stored mRNA in the spores suggests that the triggering mechanism for germination in these organisms may be at the level of translation.…”

Protein synthesis during germination of Allomyces macrogynus mitospores

“…We have recently demonstrated the presence of mRNA in ungerminated mitospores of Allomyces macrogynus (14). The mRNA was found to be associated with polysomes and was not synthesized during the period of sporogenesis, suggesting that it was derived from mRNA already present in sporangia.…”

“…This strongly suggests that spores contain mRNA which directs the protein synthesis that occurs during germination. Indeed, the presence of mRNA has been demonstrated in ungerminated fungal spores (2,6,11,14).…”