RNA synthesized during late sporulation is required for germ tube formation in Blastocladiella emersonii

Abstract

Inhibition of RNA synthesis with actinomycin D as late as 210 min ( T 210) after Blastocladiella emersonii is induced to sporulate results in complete blockage of germ tube formation in the next generation. In agreement with other reports, actinomycin D added during germination did not block germ tube formation. Protein synthesis during germination is reduced by approximately one-half when actinomycin D is added at T 210 but remains at virtually control levels when actinomycin D is added during germination. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel analyses of the abundant proteins synthesized in vivo during the first hour of germination revealed no qualitative differences in the proteins which accumulate when control cells are compared to cells treated with actinomycin D at T 210. Comparison of proteins synthesized from 20 to 40 min germination vs 40 to 60 min germination demonstrated that actinomycin D alters the temporal pattern of accumulation of some abundant proteins. The RNA synthesized after T 210 is associated with polysomes, suggesting that an mRNA fraction made in late sporulation is required for a germ tube. The available data do not exclude the possibility that a regulatory RNA synthesized during late sporulation is required for germ tube formation.