KW: heterokaryons; reverse mutation leucineless Neurospora;
My work under Ryan's tutelage. He had originally observed "adaptation""
in growth tubes with leu- Neurospora. I must have had many arguments
with him about possible mechanisms, including the most obvious: reverse
mutation. This had not previously been documented with auxotrophs!
And barring selective procedures, it was barely known at all in
Drosophila etc. Today of course it is a ubiquitous nuisance!
The main finding was that backcrosses of revertants to wild type
gave no auxotrophic progeny. This of course might be defeated by a
moderately closely linked suppressor.
More perplexing was the population dynamics of the leu+/leu- heterokaryon:
Paradoxically, leu- nuclei would prevail given any selective
platform at all. This is not understood at all. Something analgous
may occur with pantothenate +/- cf. Rowland H. Davis @ UC/I.
Am J Botany 47:648-654 1960; it may be tied in with broader issues of
heterokaryon incompatibility, though these are usually connected with
the mating type locoi.
This is discussed further by Ryan (1946) - Cold Spr Harb Symp
Not every leu+ strain is inhibited by leu-., and by TH Pittenger
& TG Brawner Genetics 46:1645-1663 1961
Ryan was concerned that the effects of leucine might be seen as
somehow lamarckian.
jl 7/25/98
Elementary question : is this selection at level of nuclei or of
competing multinucleate hyphal tips?
jl 7/16/98
Letter from Joshua Lederberg to David Perkins (March 3, 1983)