Sutter R P, Grandin A B, Dye B D, Moore W R
Biology Department, West Virginia University, Morgantown 26506, USA.
Fungal Genet Biol. 1996 Dec;20(4):268-79. doi: 10.1006/fgbi.1996.0041.
We have isolated the first mating type-specific mutants in mucoraceous fungi. Both mutants in Phycomyces blakesleeanus appear to be defective in the same gene. The gene, present in both mating types, is necessary only in cultures of the (-) mating type. The gene codes for an enzyme in sex pheromone biosynthesis. The pheromone precursor made by the mutants is detectable only in cross-feeding experiments. The biological and solubility properties of the precursor suggest the precursor is 4-dihydrotrisporin, a metabolite of beta-carotene. Separate studies with beta-carotene-deficient mutants and Compound-P, a new chemically synthesized precursor of the pheromones, imply the constitutive level of enzymes for pheromone biosynthesis in Phycomyces is extremely low. In comparison, the level of enzymes for pheromone conversion to trisporic acid is higher. The mating type-specific mutants also catalyze the conversion of (+) pheromone to trisporic acid. This finding was unexpected because literature models predicted this reaction was catalyzed by the same enzyme which catalyzed the conversion of 4-dihydrotrisporin to (-) pheromone-a reaction missing in the (-) mating type-specific mutants. Thus, we propose a revised model for trisporic acid biosynthesis.
我们已经在毛霉科真菌中分离出了首个交配型特异性突变体。布氏梨形孢中的两个突变体似乎在同一个基因上存在缺陷。该基因存在于两种交配型中，仅在（-）交配型的培养物中是必需的。该基因编码一种性信息素生物合成中的酶。突变体产生的信息素前体仅在交叉饲养实验中可检测到。该前体的生物学和溶解性特性表明其为4-二氢三孢素，即β-胡萝卜素的一种代谢产物。对β-胡萝卜素缺陷型突变体和化合物P（一种新的化学合成的信息素前体）的单独研究表明，布氏梨形孢中信息素生物合成酶的组成型水平极低。相比之下，信息素转化为三孢酸的酶水平更高。交配型特异性突变体还催化（+）信息素转化为三孢酸。这一发现出乎意料，因为文献模型预测该反应是由催化4-二氢三孢素转化为（-）信息素的同一种酶催化的——（-）交配型特异性突变体中缺少这一反应。因此，我们提出了一种修订后的三孢酸生物合成模型。
