流式细胞术在兰科植物中的应用

兰科是重要的观赏、药用园艺植物,在长期的进化演变中形成了丰富的形态类型和复杂的染色体倍性,并普遍存在内多倍性现象。挖掘兰科的遗传信息是育种研究中重要的基础工作。流式细胞术作为一种高通量的细胞分析和分选技术,在植物DNA含量、细胞周期和倍性鉴定等方面应用广泛。本文主要综述流式细胞术在兰科基因组大小测定、染色体倍性分析和内多倍性研究等方面的应用,为进一步利用流式细胞术开展兰科植物杂交育种、染色体结构、进化分类等相关研究提供参考。     

紫薇多倍体的诱导、鉴定及内多倍性研究

以紫薇子叶期幼苗为试验材料,采用不同秋水仙素浓度和时间组合处理其生长点,成功获得四倍体(2n=4x=96)和六倍体(2n=6x=144)。诱变株与二倍体对照植株形态差异明显,植株矮小粗壮,叶片变皱、粗糙,增厚,气孔密度减小,气孔保卫细胞(一对,下同)长、宽分别增大65.79%和45.01%,保卫细胞内叶绿体数量增加80.25%,且颗粒增大。四倍体花粉粒直径增大59.07%,花瓣长宽略有增加,但花序长和花朵数反而减少。人工诱导四倍体和普通二倍体茎尖都有内多倍化现象,并且前者内多倍化水平低于后者。     

Variations of endoreduplication and its potential contribution to endosperm development in rice (Oryza sativa L.)

ABSTRACT

Endoreduplication is the phenomenon by which cells increase their ploidy. Endoreduplication is initiated by the transition from the mitotic cell cycle to the endocycle, in which DNA replication occurs without a subsequent chromosome separation and cytokinesis, and is enhanced by endocycle reiteration. This process appears to play an important role in endosperm development, but the characteristics of endoreduplication in the endosperm of rice (Oryza sativa) remain unclear. To elucidate the features and variations of endoreduplication in rice endosperm, endoreduplication progression in the developing endosperm was compared among 10 cultivars based on flow cytometry and fluorescence microscopy. The flow cytometric analysis detected significant differences among 10 cultivars in the following three parameters: mean ploidy of all nuclei, the proportion of nuclei ≥6C (%E, an estimate of the initiation of the endocycle), and the mean ploidy of nuclei ≥6C (E6P, an estimate of the reiteration of the endocycle). However, no significant correlation between %E and E6P was observed, suggesting that the initiation and reiteration of the endocycle are independently regulated. Fluorescence microscopy revealed that the ploidy of the nuclei was higher in the intermediate region than in the central and peripheral regions of the endosperm. Cells with a higher ploidy were larger in the developing endosperm. Furthermore, the mean ploidy in the developing endosperm was significantly correlated with the mean cell size in the mature endosperm. These results indicate that endoreduplication progression in the endosperm differed significantly among the 10 rice cultivars and such differences may influence endosperm cell size.