RECOMBINATION AND COMPLEMENTATION OF ALBINO MUTANTS IN NEUROSPORA

On the basis of recombination and complementation studies, 27 albino mutants of Neurospora crassa can be tentatively grouped into one or the other of two closely linked units. One of the units, represented by aur, consists of several recombinational subunlts. The other, represented by al-2, contains only four mutants and also seems to be divisible. Many inter- as well as intra-unit combinations did not show complementation for the carotenoid pigments, but growth was observed in these forced heterokaryons. Such noncomplementarity is attributed to unbalanced nuclear ratio and functional incompatibility. Moreover, while the albino mutants contain only the colorless polyenes, complementing pairs produce in their heterokaryons a full spectrum of colorless and pigmented carotenoids that are ordinarily present in the wild types. The suggestion is made that these closely linked units are functionally heterocatalytic and the present material may be used to obtain a greater understanding of genic control of carotenogenesis. While the present result is not inconsistent with there being only one complex gene, in which two units resemble separate cistrons, the relevancy of interpretation at this level must rest on further understanding of the nature of complementation and noncomplementation and of the biochemistry of carotenogenesis. (auth)