Scripps Clinic and Research Foundation, 10666 N. Torrey Pines Road, 92037, La Jolla, California, USA.
Curr Microbiol. 1978;1(3):163-6. doi: 10.1007/BF02601670.
Mating inPhysarum polycephalum involves the fusion of two haploid amoebae and the differentiation of the resulting diploid zygote into a multinucleate plasmodium. Mating proceeds optimally with amoebae growing on an agar medium at pH 5.0. At pH 6.2, the amoebae still grow normally, but mating is completely blocked. The barrier at pH 6.2 is not in the differentiation step, since preformed diploids readily convert to plasmodia at this pH. The barrier can be overcome by raising the ionic strength of the agar medium; the effect, moreover, is not ion-specific. We have discovered a genetic locus,imz (ionicmodulation of zygote formation), that affects the upper pH limit for mating; the respective limits associated with the two known alleles,imz-1 andimz-2, are pH 5.6 and pH 6.0 at low ionic strength. Animz-1×imz-2 mating displays the pH 6.0 limit;imz-2 is therefore "dominant". We suggest that this new gene affects a cell component that is exposed to the exterior of the amoeba and is involved in the fusion step of mating.
在多头绒泡菌的交配过程中，两个单倍体变形虫融合，并将由此产生的二倍体合子分化为多核质体。在 pH 值为 5.0 的琼脂培养基上，变形虫生长最佳，交配也能最佳进行。在 pH 值为 6.2 时，变形虫仍能正常生长，但交配完全被阻断。在 pH 值为 6.2 时的障碍不在分化步骤，因为预先形成的二倍体在该 pH 值下很容易转化为质体。可以通过提高琼脂培养基的离子强度来克服这个障碍；此外，这种效应不是离子特异性的。我们发现了一个遗传基因座 imz（合子形成的离子调节），它影响交配的最高 pH 值限制；与两个已知等位基因 imz-1 和 imz-2 相关的相应限制分别为低离子强度时的 pH 值 5.6 和 pH 值 6.0。imz-1×imz-2 的交配显示出 pH 值 6.0 的限制；因此，imz-2 是“显性的”。我们认为这个新基因影响了一个暴露在变形虫外部的细胞成分，并参与了交配的融合步骤。
