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    银灰杨花粉母细胞减数分裂与微管骨架变化

    Meiosis and organization of microtubule of pollen mother cells in Populus canescens

    • 摘要: 减数分裂是植物有性生殖过程中配子形成的必要阶段,是生殖生物学研究领域的热点。本文以银灰杨雄花枝为研究材料,运用醋酸洋红染色法和间接免疫荧光技术,开展银灰杨花粉母细胞减数分裂及其微管骨架动态变化研究。结果表明:1)银灰杨花药颜色变化可作为初步判别其花粉母细胞减数分裂时期的形态学标记,花粉母细胞从减数分裂细线期发育至四分体时期,花药颜色从嫩绿色,经由黄绿色、微红色、浅红色、鲜红色转为深红色。2)银灰杨花粉母细胞减数分裂末期Ⅰ可观察到与着丝粒微管紧密相连的落后染色体,由于染色体两侧着丝粒微管的均衡牵引而致使其停滞于细胞板中央,不移向两极而被遗弃,造成配子染色体的不平衡,可能是导致银灰杨花粉部分败育的机制。3)银灰杨的胞质分裂属于典型的连续型胞质分裂类型,受辐射状微管系统的调节,从细胞周沿向心扩展,直至细胞质完全分离。4)银灰杨花粉中存在天然2n花粉,其发生可能与减数分裂中期Ⅱ的平行纺锤体和三极纺锤体有关。本研究首次报道了银灰杨花药颜色变化与其花粉母细胞减数分裂进程的关系,从新的角度阐释了银灰杨落后染色体的形成原因及其花粉败育机制,并探索了银灰杨天然2n花粉的发生机理,为银灰杨遗传改良策略的制定奠定了基础。

       

      Abstract: Meiosis plays an important role in gamete formation of plants during sexual reproduction. Meiosis is also a research hotspot in reproductive biology. To promote the progress of reproductive biology research in Populus canescens, meiosis and microtubule cytoskeleton of pollen mother cells (PMCs) were conducted in P. canescens by indirect immunofluorescence microscopy and aceto-carmine staining. The results showed that: 1) colors of anther could be considered as a morphological marker to discriminate meiotic stages of PMCs. With PMCs developing from leptotene to tetrad, the colors of anthers varied from peak green, yellow green, slight red, light red, fresh red to crimson. 2) Lagging chromosomes at telophase Ⅰ connected with centromeric microtubule was observed in PMCs. Owing to the balanced pull of centromeric microtubule, chromosomes did not move to the polar of PMCs and stayed at the center of cell plate, resulting in the loss of chromosomes. Therefore, it was inferred that the mechanism of aborted pollen formation in P. canescens was the unbalance of chromosome numbers of male gametes. 3) Cytokinesis in P. canescens was of a typical simultaneous-type cytokinesis, which was regulated by nuclear-based radial microtubule systems. Cytokinesis was initiated at the edge of mother cells and centripetally prolonged, up to be four separate microspores. 4) Natural 2n pollens were observed in P. canescens. Parallel and fused spindles were considered to be responsible for the 2n pollen formation. In this study, the relationship between anther color and meiotic process of PMCs was firstly reported, and the cause of lagging chromosome formation and its aborted pollen mechanism were revealed, and the mechanism of natural 2n pollen formation was discussed. Our findings will provide a platform for making strategy of genetic improvement in P. canescens.

       

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