DNA topoisomerases which remove superhelical turns in closed circular DNA have been isolated from cauliflower inflorescences using polyethylene glycol fractionation, ammonium sulfate precipitation, and column chromatography on CM-Sephadex or CM-cellulose and DNA-cellulose. Two distinct enzymes, topoisomerase-I and ATP-dependent topoisomerase, were separated clearly by CM-Sephadex or CM-cellulose, and partially characterized using agarose gel electrophoresis with plasmid pBR322 DNA. Topoisomerase-I acts like other eucaryotic DNA topoisomerases in the absence of ATP, is stimulated by spermidine and inhibited by EDTA. The ATP-dependent topoisomerase acts like topoisomerase-I only in the presence of ATP in the reaction medium, is inhibited by spermidine and EDTA, and does not introduce supertwists into closed duplex DNA or produce catenate aggregates under the present reaction conditions.

Type II DNA topoisomerase has been isolated from inflorescences of cauliflower (Brassica oleracea var. botrytis) through a sequence of polyethylene glycol fractionation, ammonium sulfate precipitation, and column chromatography on CM-Sephadex, hydroxyapatite and phosphocellulose. The molecular weight of the native enzyme, based on sedimentation coefficient (9S) and gel filtration analysis (Stokes radius, 60 Å), was estimated to be 223 000. This enzyme was able to catalyze fully the relaxation of supercoiled DNA by breaking and then rejoining the double-stranded DNA. The breaking reaction was reversible by a change in salt concentrations. When an antitumor drug, 4'-(9-acridinylamino)-methanesulfon-m-anisidide, was added to the topoisomerase reaction, DNA cleavage fragments were accumulated; and this suggested that the drug interfered with the reaction at the rejoining step. This enzyme also catalyzed the formation of DNA catenanes in the presence of 8% polyethylene glycol or histone H1, while few catenanes were formed in the presence of spermidine, which was highly effective on a bacterial enzyme.

Cytoplasmic inheritance of pollen abortion has been reported in some species as well as in the species and genus-hybrids. In most cases, meiosis in PMC proceeds normally, but the young pollen grains degenerate before anthesis, indicating that the degeneration is due to a disharmony between nucleus and cytoplasm. The present study deals chiefly with the preliminary investigation on the free amino acids and amides in anthers of male-sterile wheat and maize. The male-sterile wheat used in the present investigation has the genomes of Triticum durum, AABB, substituted in the cytoplasm of Aegilops ovata by successive backcrosses (Fukasawa, 1953). The male-sterile maize is a strain, WF 9, which was supplied by Dr. Bauman, Department of Agronomy,

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