Cohesin, a multisubunit protein complex, is required for holding sister chromatids together during mitosis and meiosis. The recruitment of cohesin by the sister chromatid cohesion 2/4 (SCC2/4) complex has been extensively studied in Saccharomyces cerevisiae mitosis, but its role in mitosis and meiosis remains poorly understood in multicellular organisms, because complete loss-of-function of either gene causes embryonic lethality. Here, we identified a weak allele of Atscc2 (Atscc2-5) that has only minor defects in vegetative development but exhibits a significant reduction in fertility. Cytological analyses of Atscc2-5 reveal multiple meiotic phenotypes including defects in chromosomal axis formation, meiosis-specific cohesin loading, homolog pairing and synapsis, and AtSPO11-1-dependent double strand break repair. Surprisingly, even though AtSCC2 interacts with AtSCC4 in vitro and in vivo, meiosis-specific knockdown of AtSCC4 expression does not cause any meiotic defect, suggesting that the SCC2-SCC4 complex has divergent roles in mitosis and meiosis. SCC2 homologs from land plants have a unique plant homeodomain (PHD) motif not found in other species. We show that the AtSCC2 PHD domain can bind to the N terminus of histones and is required for meiosis but not mitosis. Taken together, our results provide evidence that unlike SCC2 in other organisms, SCC2 requires a functional PHD domain during meiosis in land plants.

粘连蛋白是一种多亚基蛋白复合物，在有丝分裂和减数分裂过程中将姐妹染色单体保持在一起是必需的。姐妹染色单体粘连 2/4 (SCC2/4) 复合体对粘连蛋白的募集已在酿酒酵母有丝分裂中得到了广泛研究，但其在多细胞生物有丝分裂和减数分裂中的作用仍然知之甚少，因为任一者的功能完全丧失。基因导致胚胎死亡。在这里，我们发现了Atscc2 ( Atscc2-5 ) 的一个弱等位基因，它在营养发育方面只有微小的缺陷，但表现出生育力的显着降低。 Atscc2-5的细胞学分析揭示了多种减数分裂表型，包括染色体轴形成缺陷、减数分裂特异性粘连蛋白负载、同源配对和突触以及AtSPO11-1依赖性双链断裂修复。令人惊讶的是，即使 AtSCC2在体外和体内与 AtSCC4 相互作用，减数分裂特异性敲除AtSCC4表达不会导致任何减数分裂缺陷，表明 SCC2-SCC4 复合物在有丝分裂和减数分裂中具有不同的作用。来自陆地植物的 SCC2 同源物具有其他物种中未发现的独特植物同源域 (PHD) 基序。我们发现 AtSCC2 PHD 结构域可以与组蛋白的 N 末端结合，并且是减数分裂所必需的，但不是有丝分裂所必需的。总而言之，我们的结果提供了证据，表明与其他生物体中的 SCC2 不同，SCC2 在陆地植物减数分裂期间需要功能性 PHD 结构域。