Zhao Qinzheng, Xiong Zhenhui, Cheng Chunyan, Wang Yuhui, Feng Xianbo, Yu Xiaqing, Lou Qunfeng, Chen Jinfeng
State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
Plant Biotechnol J. 2025 Mar;23(3):887-899. doi: 10.1111/pbi.14546. Epub 2024 Dec 11.
The interaction dynamics of homologous chromosomes during meiosis, such as recognition, pairing, synapsis, recombination, and segregation are vital for species fertility and genetic diversity within populations. Meiotic crossover (CO), a prominent feature of meiosis, ensures the faithful segregation of homologous chromosomes and enriches genetic diversity within a population. Nevertheless, visually distinguishing homologous chromosomes and COs remains an intractable challenge in cytological studies, particularly in non-model or plants with small genomes, limiting insights into meiotic dynamics. In the present study, we developed a robust and reliable enhanced haplotype oligo-painting (EHOP) technique to image small amounts of oligos, enabling visual discrimination of homologous chromosomes. Using EHOP developed based on sequence polymorphisms and reconstructed oligonucleotides, we visually distinguished parental and most recombinant chromosomes in cucumber F hybrids and F populations. Results from EHOP revealed that meiotic CO events preferentially occur in the 30-60% intervals of chromosome arms with lower sequence polymorphisms and significant recombination bias exists between cultivated and ancestral chromosomes. Due to the occupation of extensive heterochromatin occupancy, it is not yet possible to precisely identify the meiotic COs present in the central portion of chr2 and chr4. Notably, CO accessibility was universally detected in the cytological centromere region in F populations, a feature rarely observed in crops with large genomes. EHOP demonstrated exceptional performance in distinguishing homologous chromosomes and holds significant potential for broad application in studying homologous chromosome interactions.
减数分裂过程中同源染色体的相互作用动态，如识别、配对、联会、重组和分离，对于物种育性和种群内的遗传多样性至关重要。减数分裂交叉（CO）是减数分裂的一个显著特征，可确保同源染色体的准确分离并丰富种群内的遗传多样性。然而，在细胞学研究中，尤其是在非模式生物或小基因组植物中，直观区分同源染色体和CO仍然是一项棘手的挑战，这限制了对减数分裂动态的深入了解。在本研究中，我们开发了一种强大且可靠的增强型单倍型寡核苷酸荧光原位杂交（EHOP）技术，用于对少量寡核苷酸进行成像，从而能够直观区分同源染色体。利用基于序列多态性和重建寡核苷酸开发的EHOP，我们在黄瓜F1杂种和F2群体中直观区分了亲本染色体和大多数重组染色体。EHOP的结果表明，减数分裂CO事件优先发生在染色体臂30%-60%的区间内，这些区间的序列多态性较低，并且栽培染色体和祖先染色体之间存在显著的重组偏差。由于存在广泛的异染色质占据，目前尚无法精确识别2号和4号染色体中部存在的减数分裂CO。值得注意的是，在F2群体的细胞学着丝粒区域普遍检测到CO可及性，这一特征在大基因组作物中很少观察到。EHOP在区分同源染色体方面表现出色，在研究同源染色体相互作用方面具有广泛应用的巨大潜力。
