ADAPTATION IN PANTOTHENATE-REQUIRING NEUROSPORA II. NUCLEAR COMPETITION DURING ADAPTATION

摘要: DAVIS, R. H. (U. Michigan, Ann Arbor.) Adaptation in pantothenate-requiring Neurospora. II. Nuclear competition during adaptation. Amer. Jour. Bot. 47(8): 648-654. Illus. 1960.-The process of adaptation Neurospora was studied by the use heterocaryons constituted pan-i strain and a modified strain, pan-I m, derived from it. Although pan-l-m homocaryons grow well on pantothenate concentration which grows little or not at all, nuclei often have selective advantage + pan-l-m. grown same medium. This results non-adaptive changes nuclear ratios labile growth rates heterocaryons. does occur when is limiting to either homocaryon. The are discussed, related past work ratio hetercaryons. ADAPTATION Neurospora, sense genetic population mycelium lead more rapid growth, has been no means thoroughly investigated. coenocytic organization mycelia allows numerous cooperate activities single cytoplasmic unit. Through mutation through fusion genetically dissimilar mycelia, heterocaryon may arise there heterogeneity population. Mutant types will sustain normal pure cultures may, combined "balanced heterocaryon," contribute phenotype mutual complementation wild type alleles mutant genes involved. Since autonomous, but interact with one another an integrated cellular system, change frequencies complex phenomenon than populations uninucleate, unicellular organisms such as bacteria. adapting crassa subject this paper. Previous investigators brought forth 2 different proposals regarding interactions between components balanced heterocaryon. Beadle Coonradt (1944) suggested, though without definitive evidence, that altered selection among hyphae growing frontier mycelium. They assumed individual determined their own ratios, for those optimal leads establishment rate l Received publication December 19, 1959. done while author U. S. Public Health Service Predoctoral Research Fellow National Cancer Institute. Submitted portion dissertation partial fulfillment requirements degree Ph.D., Department Biology, Harvard University, 1958. investigation conducted Biological Laboratories University. It pleasure thank following people critical discussion work: Drs. K. C. Atwood, W. T. Ebersold, P. Levine, J. Raper, F. Ryan, l'. Snider. (and ratio) whole. Pittenger Atwood (1956), after extensive matter, maintained hyphal "rarely, if ever, operates" alter fully established heterocaryon, even cases would result higher rate. idea supported experiments biochemically types, carefully synthesized highly disparate grew stable submaximal long periods time. referable scarcity 1 types. stability presumed depend upon equal division tvpes, dependence mycelial larger proximal them, continual mixing streaming anastomosis. A not, apparently, encountered above-mentioned investigations described Ryan Lederberg (1946; cf. 1946). Adaptations leucineless (leu-i) concentrations leucine were observed take place occurrence proliferation backmutant (leu-i +) nuclei. found, however, leu-i inhibited ths sectors leucine, leading (i.e., less favorable high rate) Data reminiscent behavior reported Emerson (1947, 1948) Cushing (1946), working adaptations sulfonamides. Such cannot be accounted terms simple ratios. Another case pantothenic-less pan-i, previously (Davis, 1960). strains, isolated asexually singrle panto-