leucine present continuously. There was no dif- 

 ference between the incorporation in the control 

 culture and the one with actinomycin. 



Because of Paul Gross' results with em- 

 bryos (9), I'd like to speculate even more: if, 

 during these stages, we look at pulse-labeled 

 RNA on sucrose gradients (we are just beginning 

 to do this), the cells make RNA during the 

 whole time, but it is not ribosomal RNA. The 

 new RNA seems to be polydisperse, and in the 

 spore it is very heterogeneous on gradients. It 

 looks like a nice, classical bacterial messenger- 

 RNA pattern. The new RNA does not match the 

 ribosomal peaks. As soon as germination be- 

 gins, we also get the same effect that Paul 

 described for embryos - very "hot" labeling in 

 the sRNA region. I was originally concerned 

 that the RNA might be degraded and that some- 

 thing was wrong. I am only too happy to see that 

 the same results were obtained with embryos. 

 It isn't until actinomycin has its effect, at about 

 30-40 min, that we can show synthesis of ribo- 

 somal RNA. This suggests that during the first 

 30 min, the cell is operating with pre-existing 

 RNA, that the spores, in fact, have been pre- 

 coded for the earliest events. I say pre-coded 

 because of the observation, not because we have 

 direct evidence for it. It is just as mysterious 

 to me as it is, perhaps, to those who work with 

 sea urchins. We did look for polysomes and could 

 not find them. After hearing Paul, I was struck 

 by the fact that two cell types which, in part at 

 least, have a similar function (to be non- synthetic 

 and yet ready to begin synthesis at a certain 

 time) seem to be so similar in their patterns of 

 early RNA and protein synthesis. 



KAHN: How long can a spore be maintained 

 before it becomes inviable? 



LOVETT: I've never really determined 

 this, mostly because Tve been interested in just 

 the reverse. When we harvest our spores, we 

 try to collect only those that have been dis- 

 charged over a short interval. We then hold 

 them on ice until the experiment begins, which 

 means a matter of half an hour from the time 

 we isolate them. 



KAHN: Then zoospores can probably be 

 kept a long time? 



LOVETT: Well, actually they can swim 

 almost for days. 



CANTDSrO: I can answer that question fairly 

 positively. Some spores can remain viable for 

 at least 24 hr, probably 36 hr, as swimmers. 

 They are getting their energy reserves from 

 within, not without, because this can happen in 

 water. We know they have a sizeable polysac- 



charide pool. 



TS'O: Did I hear correctly? In the begin- 

 ning you said that you think the ribosomes may 

 be made in the cytoplasm? 



LOVETT: No, what I was suggesting was 

 that one of the ways the cap might have been 

 formed was by synthesis of new ribosomes by 

 turnover and retention of the newly produced 

 ribosomes just outside the nucleus. Our evi- 

 dence suggests that the ribosomes were made 

 before the stage of cap formation. I didn't mean 

 in the cytoplasm. 



KAHN: Let me restate my question. Does 

 the resistant sporangium, wherein I assume the 

 nuclear caps (ribosomes) are being formed, re- 

 main viable for 24 or 36 hours? 



LOVETT: I'm not sure of your question. 

 These spores can't be held very long. They have 

 a high metabolic rate and they eventually dis- 

 integrate if not allowed to germinate. 



KAHN: Tm talking about prior to release. 

 K the resistant sporangium is, indeed, "re- 

 sistant". 



LOVETT: The resistant sporangium is re- 

 sistant, but this isn't the resistant sporangium 

 we've been working with. 



KAHN: I'm aware of that. 



CANTINO: There are no spores in the re- 

 sistant sporangium even when it is mature. 



LOVETT: The resistant sporangium is 

 going to produce spores. Ed Cantino knows a 

 lot more about the form it is in than I do. I 

 haven't looked at this. 



GROSS: What is the function of this gamete? 

 Is it just dispersion by swimming or is it stor- 

 age for a long period of time? 



CANTINO: The resistant sporangium is a 

 thick-walled structure. It appears to tide the 

 organism over unfavorably environmental con- 

 ditions in nature. We've had R.S. sitting in the 

 shelf for almost twenty years, now, practically 

 dry, and some of them are still viable. As far 

 as we know, there are no pre-formed spores in 

 them. Spores are induced to form once the re- 

 sistant sporangium is put in water. Then the 

 protoplast cleaves up into spores, the spores 

 swim out, and to all intents and purposes they 

 are like the spores Jim Lovett uses. 



LOVETT: That takes about 8 hr ; the process 

 I have described in zoosporangia takes 3 hr. 

 Our cultures go a little slower than Ed's be- 

 cause of the way we treat them. 



PAPACONSTANTINOU: I'm sorry I didn't 

 get this. Did you mention where the new ribo- 

 somal synthesis starts? 



LOVETT: New ribosomal- RNA synthesis 



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