Term of Award

Spring 2000

Degree Name

Master of Science in Biology

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Sara Neville Bennett

Committee Member 1

Wayne A. Krissinger

Committee Member 2

Oscar J. Pung

Abstract

Three mutants, SS-316, SS-398, and SS-930, of the filamentous fungus Neurospora crassa were isolated in our laboratory, the Georgia Southern Neurospora Laboratory, following UV induction and filtration concentration. All three isolates have altered morphology when compared to wild type N. crassa.

Isolate SS-316

Isolate SS-316 is osmotic-sensitive and fails to grow on medium supplemented with 4% NaCI. However, the morphology of SS-316 resembles that of wild type, with the exception of conidia forming in clumps, and differs from that of the typical osmotic-sensitive strains, which are characterized by the production of few conidia, intense pigmentation, and close-cropped aerial hyphae that tend to rupture and bleed.

Isolate SS-316 and its first and second backcross progeny were characterized for hyphal elongation, biomass, conidial quantification, conidial germination, and wettable characteristic. Differences were noticed between original isolate SS-316 and its first and second backcross progeny in hyphal elongation and biomass.

In crosses of the first backcross progeny of SS-316 to Wild Type 74, the traits of osmotic sensitivity and clumpy conidia each segregated 1:1 and the lack of recombinant progeny indicated that the traits were co-segregating. This is consistent with mutant traits of SS-316 being pleiotrophic effects of a single gene under Mendelian control.

Genetic mapping of SS-316 has shown that SS-316 is the first osmotic-sensitive mutant mapped to Linkage Group V and is therefore a new osmotic-sensitive osmotic-sensitive mutant locus of N. crassa. It is proposed that SS-316 be designated os-12.

Isolate SS-398

Isolate SS-398 is a morphological mutant that differs from wild type N. crassa. SS-398 is a spreading colonial which initially has restricted colonial growth, but with maturity the morphology of the mutant resembles that of wild type. Isolate SS-398 differs additionally from wild type N. crassa since the conidia of SS-398 do not separate in the tap test.

Isolate SS-398 and its first and second backcross progeny were characterized for hyphal elongation, biomass, conidial quantification, conidial germination, and wettable characteristic. No differences were noticed between original isolate SS-398 and its first and second backcross progeny. Isolate SS-398 and its backcross progeny were observed to have a lower hyphal elongation, biomass, and number of free conidia per ml when compared to Wild Type 74.

In crosses of SS-398 to Wild Type 74, the traits of altered morphology and conidial separation each segregated 1:1 and the lack of recombinant progeny indicated that the traits were co-segregating. This is consistent with mutant traits of SS-398 being pleiotrophic effects of a single gene under Mendelian control.

Genetic analysis of SS-398 has shown that SS-398 is tightly linked to lys-1 locus in the left arm of Linkage Group V. Isolate SS-398 appears to be a new morphological mutant of N. crassa.

Isolate SS-930

Isolate SS-930 is a morphological mutant that differs from wild type N. crassa. Isolate SS-930 is a tight colonial which displays tightly restricted mycelial growth at all times. Isolate SS-930 differs additionally from wild type N. crassa since the conidia of SS-930 do not separate in the tap test.

Isolate SS-930 and its first and second backcross progeny were characterized for hyphal elongation, biomass, conidial quantification, conidial germination, and wettable characteristic. No differences were noticed between original isolate SS-930 and its first and second backcross progeny. Isolate SS-930 and its backcross progeny were observed to have a lower hyphal elongation, biomass, and number of free conidia per ml when compared to Wild Type 74. The mycelium of SS-930 and its backcross progeny was observed to be hydrophilic instead of hydrophobic as is the mycelium of wild type mycelium.

In crosses of SS-930 to Wild Type 74, the traits of altered morphology and conidial separation each segregated 1:1 and the lack of recombinant progeny indicated that the traits were co-segregating. This is consistent with mutant traits of SS-930 being pleiotrophic effects of a single gene under Mendelian control.

Genetic analysis of SS-930 has placed this mutant in Linkage Group V. The locus of SS-930 is located by 25.8% recombination to the leu-5 locus.

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