Figure 2.
tim9 gene is essential in N. crassa. (A) Sheltered heterokaryon containing the tim9RIP mutant. The box depicts the heterokaryon produced during the sheltered RIP cross described in MATERIALS AND METHODS. Circles represent the genetically distinct nuclei that make up the heterokaryon. Nucleus 1 contains only the nonfunctional RIPed version of tim9, whereas nucleus 2 contains a wild-type version of the gene. Only genes relevant to the growth and manipulation of the sheltered heterokaryon are shown. (B) The level of Tim9 is reduced in cultures where the nucleus containing the RIPed gene is increased in number. The sheltered heterokaryon (A) and an acriflavine resistant control strain (Host III) were grown in the presence of acriflavine and tryptophan and mitochondria were isolated. Mitochondrial proteins were separated by SDS-PAGE and blotted to nitrocellulose. The blot was decorated with antibodies against the indicated proteins. (C) Scoring of single colonies from the heterokaryotic strain described in A (ade, adenine; trp, tryptophan).