Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560 012, India.
J Biosci. 2011 Aug;36(3):505-16. doi: 10.1007/s12038-011-9084-3.
In the trishanku (triA-) mutant of the social amoeba Dictyostelium discoideum, aggregates are smaller than usual and the spore mass is located mid-way up the stalk, not at the apex. We have monitored aggregate territory size, spore allocation and fruiting body morphology in chimaeric groups of (quasi-wild-type) Ax2 and triA- cells. Developmental canalisation breaks down in chimaeras and leads to an increase in phenotypic variation. A minority of triA- cells causes largely Ax2 aggregation streams to break up; the effect is not due to the counting factor. Most chimaeric fruiting bodies resemble those of Ax2 or triA-. Others are double-deckers with a single stalk and two spore masses, one each at the terminus and midway along the stalk. The relative number of spores belonging to the two genotypes depends both on the mixing ratio and on the fruiting body morphology. In double-deckers formed from 1:1 chimaeras, the upper spore mass has more Ax2 spores, and the lower spore mass more triA- spores, than expected. Thus, the traits under study depend partly on the cells' own genotype and partly on the phenotypes, and so genotypes, of other cells: they are both autonomous and non-autonomous. These findings strengthen the parallels between multicellular development and behaviour in social groups. Besides that, they reinforce the point that a trait can be associated with a genotype only in a specified context.
在有丝分裂三（triA-）突变体的社会变形虫盘基网柄菌中，聚集体比通常的小，并且孢子团位于柄的中途，而不是在顶端。我们监测了嵌合体（准野生型）Ax2 和 triA-细胞的聚集区大小、孢子分配和子实体形态。在嵌合体中，发育管道化破裂导致表型变异增加。少数 triA-细胞导致大部分 Ax2 聚集流破裂；这种效应不是由于计数因子。大多数嵌合子实体类似于 Ax2 或 triA-。其他是双层的，有一个单一的柄和两个孢子团，一个在末端，一个在柄的中途。属于两种基因型的孢子的相对数量既取决于混合比，也取决于子实体形态。在由 1:1 嵌合体形成的双层体中，上部孢子团的 Ax2 孢子比预期的多，下部孢子团的 triA-孢子比预期的多。因此，研究中的特征部分取决于细胞自身的基因型，部分取决于其他细胞的表型，因此基因型是自主的和非自主的。这些发现加强了多细胞发育和社会群体行为之间的相似性。除此之外，它们还强调了一个特征只能在特定的环境中与一个基因型相关的观点。
