The timing of ribonucleic acid synthesis during the germination of heat-activated Dictyostelium discoideum spores

Abstract

To observe changes in the rate of RNA synthesis during Dictyostelium discoideum spore germination, we have pulse labeled germinating spores with [3H]uracil at stage-specific intervals. The labeled RNAs have been fractionated on 1.7 and 10% polyacrylamide gels. Additionally we have monitored the total changes in ribonucleic acid content during germination. In general, the rate of synthesis of various RNA species appears to increase noncoordinately, while the total RNA content remains unchanged during germination. This may indicate extensive RNA turnover during germination. Little or no RNA synthesis is observed during the first pulse period (postactivation lag). During the 1-2-h pulse period, 25, 17, 5.8, and 5 S RNA were all synthesized. The synthesis of these species increased with each pulse period, with the greatest amount of synthesis occurring during the final 3-4-h pulse. The synthesis of 4 S RNA initiated during the 2-3-h pulse and increased during the final 3-4-h pulse. The percentage of poly(A) + RNA increased with each time period from 0.1% of the total labeled RNA at the 0-1-h pulse period to 10% of the total RNA synthesized at the 2-3-h pulse time. During the final pulse period (3-4 h), this level dropped to 6%. Analysis of acid-soluble extracts from dormant spores revealed relatively high levels of the four ribonucleoside 5'-triphosphates. These levels remained unchanged during the 1st h of germination. Thus RNA synthesis during the postactivation lag stage of germination does not appear to be limited by precursor availability and may involve other regulatory mechanisms.

Germination of Dictyostelium discoideum spores. A phosphorus-31 NMR analysis

“…Interestingly, only purine nucleoside triphosphates (ATP/GTP) were represented in significant amounts in spores, and the amount of pyrimidine nucleoside triphosphates (CTP/UTP) was at least 15-20 times lower. Similar results were reported previously by using HPLC of extracts from dormant spores (Hamer & Cotter, 1983). This was not the case for vegetative °Results are means ± SEM ( = 3).…”

Patterning of development in Dictyostelium discoideum: factors regulating growth, differentiation, spore dormancy, and germination

“…Interestingly, only purine nucleoside triphosphates (ATP, GTP) are represented in significant amounts in spores, and the amount of pyrimidine nucleoside triphosphates (CTP, UTP) were found to be at least 15-20 times lower (Klein, G., et al 1988). Similar results were obtained using HPLC extracts from dormant spores (Hamer and Cotter 1983). This is not the case in vegetative amoebae where the purine/pyrimidine ratio was found to be 2.7 (Satre et al 1986) or in nascent amoebae arising from germinated spores (Klein, G., et al 1988).…”

Analysis of Phakopsora pachyrhizi transcript abundance in critical pathways at four time-points during infection of a susceptible soybean cultivar using deep sequencing

“…The low number of transcripts identified at 15 sai compared to other time-points in the present data set suggests that there is no latent pool of mRNAs present in P. pachyrhizi urediniospores as well. Even though the levels of adenosine triphosphate, guanosine triphosphate, cytidine triphosphate, and uridine triphosphate in P. pachyrhizi urediniospores are unknown, in other fungi such as dormant spores of Dictyostelium discoidenum, the relative levels of these nucleotides is greater than or equal to their levels observed in germinated spores [41]. All together, this suggests that RNA synthesis can occur rapidly after P. pachyrhizi urediniospores are deposited on the soybean leaf and even before that point which is consistent with the high level of RNA polymerase expression 15 sai exposed in the previous section.…”