Lacy Kip D, Hart Taylor, Kronauer Daniel J C
Laboratory of Social Evolution and Behavior, The Rockefeller University, New York, NY, USA.
Howard Hughes Medical Institute, New York, NY, USA.
Nat Ecol Evol. 2024 Aug;8(8):1522-1533. doi: 10.1038/s41559-024-02455-z. Epub 2024 Jul 16.
According to Mendel's second law, chromosomes segregate randomly in meiosis. Non-random segregation is primarily known for cases of selfish meiotic drive in females, in which particular alleles bias their own transmission into the oocyte. Here we report a rare example of unselfish meiotic drive for crossover inheritance in the clonal raider ant, Ooceraea biroi, in which both alleles are co-inherited at all loci across the entire genome. This species produces diploid offspring parthenogenetically via fusion of two haploid nuclei from the same meiosis. This process should cause rapid genotypic degeneration due to loss of heterozygosity, which results if crossover recombination is followed by random (Mendelian) segregation of chromosomes. However, by comparing whole genomes of mothers and daughters, we show that loss of heterozygosity is exceedingly rare, raising the possibility that crossovers are infrequent or absent in O. biroi meiosis. Using a combination of cytology and whole-genome sequencing, we show that crossover recombination is, in fact, common but that loss of heterozygosity is avoided because crossover products are faithfully co-inherited. This results from a programmed violation of Mendel's law of segregation, such that crossover products segregate together rather than randomly. This discovery highlights an extreme example of cellular 'memory' of crossovers, which could be a common yet cryptic feature of chromosomal segregation.
根据孟德尔第二定律，染色体在减数分裂过程中随机分离。非随机分离主要见于雌性自私减数分裂驱动的情况，即特定等位基因会偏向自身向卵母细胞的传递。在此，我们报告了克隆劫掠蚁（Ooceraea biroi）中一种罕见的无私减数分裂驱动以实现交叉遗传的例子，在该物种中，整个基因组的所有位点上两个等位基因都是共同遗传的。该物种通过同一减数分裂产生的两个单倍体核融合，孤雌生殖产生二倍体后代。如果交叉重组后染色体进行随机（孟德尔式）分离，这个过程会因杂合性丧失而导致快速的基因型退化。然而，通过比较母亲和女儿的全基因组，我们发现杂合性丧失极为罕见，这增加了在O. biroi减数分裂中交叉很少发生或不存在的可能性。通过结合细胞学和全基因组测序，我们表明交叉重组实际上很常见，但杂合性丧失得以避免，因为交叉产物被忠实地共同遗传。这是由于对孟德尔分离定律的程序性违反导致的，即交叉产物一起分离而非随机分离。这一发现突出了交叉的细胞“记忆”的一个极端例子，这可能是染色体分离的一个常见但隐秘的特征。
