Stable Messenger Ribonucleic Acid and Germination ofMyxococcus xanthusMicrocysts

Abstract

We have examined germination, protein synthesis and ribonucleic acid (RNA) synthesis by microcysts of the fruiting myxobacterium Myxococcus xanthus . The morphological aspects of microcyst formation were completed at about 2 hr after induction had begun. In such microcysts, germination, RNA synthesis, and protein synthesis were inhibited by actinomycin D (Act D). At 6 hr after induction, germination and protein synthesis had become relatively resistant to Act D, whereas RNA synthesis was inhibited by about 95%. Experiments with 3 H-Act D indicated that the deoxyribonucleic acids of both young and old microcysts bind Act D equally. Resistance of germination to Act D was acquired 4 to 5 hr after induction of microcyst formation, and was due to an Act D-sensitive synthesis at that time. Vegetative cells and microcysts were pulsed with uridine- 5 - 3 H and chased for 60 min; the RNA was extracted and analyzed by means of sucrose density gradient centrifugation and gel electrophoresis. Both microcysts and vegetative cells were found to contain grossly the same types of RNA in the same proportions. RNA pulse-labeled in microcysts was more stable than that in vegetative cells. No particular portions of the microcyst pulse-labeled RNA were selectively stabilized. These data indicate that a stable messenger RNA required for synthesis of germination proteins was synthesized during microcyst formation. This may be the same as the RNA synthesized 4 to 5 hr after initiation of microcyst formation. We suggest that the existence of such stable messenger RNA in microcysts is consistent with the limited biosynthetic activities of such cells.

Changes in ribonucleases during differentiation (spherulation) of Physarum polycephalum

“…The labeling pattern of RNA during germination are similar to those during growth in contrast to the results during spherulation (CHET and RUSCH 1970a). These findings are similar to those reported for microcysts of Myxococcus xanthus (RAMSEY andDWORKIN 1970, JUENGST and and for zoospores of Blastocladiella emersonii (LOVETT 1968). These latter authors have suggested that stable messengers code for different proteins at the time of germination and that germination proteins are of two general types: hydrolytic enzymes formed prior to the breakdown of the cell wall, and structural proteins, which are essential for development.…”

Macromolecular Synthesis During the Germination of Saccharomyces cerevisiae Spores

“…Brambl and Van Etten (7) showed that protein synthesis occurred before RNA synthesis during the germination of B. theobromae spores. Most commonly, however, RNA synthesis precedes protein synthesis during germination of most of the fungal spores examined (1, 3,4,15,22,24,36). The possibility that the initial proteins synthesized are dependent upon a preexisting stable messenger RNA (mRNA) has not been excluded.…”

“…RNA is the first macromolecule to increase during germination of fungal spores of Aspergillus nidulans (3), A. niger (36), A. orvzae (22), Microsporum gypseum (4), Schizophvllum commune (1), Mvxococcus xanthus (24), and Neurospora crassa (16). This is followed by an increase in protein and the onset of DNA synthesis.…”

Podospora anserina mutant defective in protoperithecium formation, ascospore germination, and cell regeneration

“…Thus it may be supposed that some of the defects associated with modx were the consequence of a disorder in the control of stable mRNA's which, in turn, resulted in a deviation of the normal physiology of stationary cells and ascospores. This hypothesis is not unlikely, since stationary cells (23,26,29) and fungal spores (11,17,27,33) This work was supported by the Conseil Scientifique de l'Universite de Bordeaux II, the Centre National de la Recherche Scientifique (Equipe de Recherche Associee no. 485), the Institut National de la Sante et de la Recherche M6dicale ("Mecanismes cellulaires et moleculaires du vieillissement"), and the Fondation pour la Recherche Medicale.…”