Banerjee Parul, Singh Bashisth N
Genetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221 005, India.
J Genet. 2017 Mar;96(1):97-107. doi: 10.1007/s12041-017-0746-2.
Making interspecific hybridizations, where possible remains an unparalleled option for studying the intricacies of speciation. In the Drosophila bipectinata species complex comprising of four species, namely D. bipectinata, D. parabipectinata, D. malerkotliana and D. pseudoananassae, interspecific hybrids can be obtained in the laboratory, thus bequeathing an ideal opportunity for studying speciation and phylogeny. With the view of investigating the degree of divergence between each species pair, we planned to study the polytene chromosomes of the F hybrids, as it would mirror the level of compatibility between the genomes of the parental species. Two sets of crosses were made, one involving homozygous strains of all four species from India and the other including homozygous strains from different places across the globe. Polytene chromosomes of F larvae from both sets of crosses had similar configurations. In F larvae from crosses involving D. bipectinata, D. parabipectinata and D. malerkotliana, complex configurations (depicting overlapping inversions) could be detected in different arms. However, they were fairly synapsed, indicating that the differences are only at the level of gene arrangements. The polytene chromosomes of larvae obtained by crossing D. pseudoananassae with the other three species were very thin with gross asynapsis in all the arms, demonstrating that the genome of D. pseudoananassae is widely diverged from rest of the species. The overlapping inversions (reflected in complex configuration), are inferred in the light of earlier chromosomal studies performed in this complex.
在可能的情况下进行种间杂交，仍然是研究物种形成复杂性的一种无与伦比的选择。在由四个物种组成的双栉果蝇物种复合体中，即双栉果蝇、拟双栉果蝇、马勒科特利亚纳果蝇和拟暗果蝇，可以在实验室中获得种间杂种，从而为研究物种形成和系统发育提供了一个理想的机会。为了研究每对物种之间的差异程度，我们计划研究F1杂种的多线染色体，因为它能反映亲本物种基因组之间的兼容程度。进行了两组杂交，一组涉及来自印度的所有四个物种的纯合品系，另一组包括来自全球不同地方的纯合品系。两组杂交产生的F1幼虫的多线染色体具有相似的构型。在涉及双栉果蝇、拟双栉果蝇和马勒科特利亚纳果蝇的杂交产生的F1幼虫中，可以在不同的臂上检测到复杂的构型（显示重叠倒位）。然而，它们相当配对，表明差异仅在基因排列水平。将拟暗果蝇与其他三个物种杂交获得的幼虫的多线染色体非常细，所有臂上都有明显的不配对，这表明拟暗果蝇的基因组与其他物种有很大差异。根据此前在该复合体中进行的染色体研究推断出重叠倒位（反映在复杂构型中）。
