半蒴苣苔属植物染色体制片优化及染色体数目和倍性研究

Optimization of chromosome preparation and chromosome number and ploidy in Hemiboea

关键词:  苦苣苔科, 半蒴苣苔属, 叶片水培生根, 染色体数目, 基因组倍性

Key words:  Gesneriaceae, Hemiboea, hydroponic rooting for cutting leaves, chromosome number, genome ploidy

摘要:

染色体数目和倍性是系统与进化生物学和遗传学研究中十分重要的基础信息。为探索半蒴苣苔属染色体制片的适宜条件以及染色体数目的进化模式及其与物种的进化关系,该研究基于半蒴苣苔属染色体数目的进化历史,并根据该属植物具有叶片扦插繁殖的特性,采用叶片水培生根法获取半蒴苣苔(Hemiboea subcapitata)、弄岗半蒴苣苔(H. longgangensis)、龙州半蒴苣苔(H. longzhouensis)、江西半蒴苣苔(H. subacaulis var. jiangxiensis)、华南半蒴苣苔(H. follicularis)和永福半蒴苣苔(H. yongfuensis)6种植物的根尖材料,分析不同实验条件对染色体制片效果的影响,对染色体制片实验的条件进行优化及染色体计数,结果表明:(1)9:30—10:00取材,解离10 min以及染色15 min为半蒴苣苔属染色体制片的适宜条件。(2)上述6种半蒴苣苔属植物均为二倍体,染色体数目均为32(2n=2x=32)。(3)除个别物种染色体数目有变化以外,该属大部分物种染色体数目可能为2n=2x=32且染色体数目变化可能是非整倍化的作用,与物种进化没有明显关系。该研究结果为半蒴苣苔属以及具有类似叶片再生植株特性类群的染色体制片提供了参考,并为该类群的分类、系统进化等方面的研究提供了启示。

Abstract:

Chromosome number and genome ploidy are crucial basic information for systematic evolutionary biology and genetics. Hemiboea, a genus of Gesneriaceae, with about 44 species, is mainly distributed in southern China, which have important medicinal and ornamental values. It is difficult to obtain suitable root tips for the chromosome preparation because of their small twining roots and small chromosomes. So far, only the chromosome numbers from three species of Hemiboea have been reported, while the chromosome numbers and ploidy of most species are unknown. The relationship between the pattern of chromosome number evolution and species evolution is also unclear. In this study, in order to explore the optimal conditions for chromosome preparation and the relationship between chromosome numbers and species evolution of Hemiboea, firstly, the root tips of six species(including H. subcapitata, H. longgangensis, H. longzhouensis, H. subacaulis var. jiangxiensis, H. follicularis and H. yongfuensis), which were generated by the method of hydroponic rooting for cutting leaves based on the characteristics of leaf cuttage propagation of plants in Hemboea, were used for the chromosome preparation experiments. Then, the effects of different experimental conditions on chromosome preparation were assessed. Next, the conditions were optimized and the chromosome counting was performed. Finally, the evolutionary history of chromosome numbers in Hemiboea and the related genera including Anna and Loxostigma were traced based on the molecular phylogenetic relationships, and the evolutionary pattern of chromosome numbers and relationships with species evolution were studied. The results were as follows:(1)The optimal conditions for karyotype preparation of the plants in Hemiboea were sampling during 9:30-10:00, dissociating for 10 min, and dyeing for 15 min.(2)All the six species of Hemiboea were diploid and with 32 chromosome numbers(2n=2x=32).(3)Except for a few species in the genus, the chromosome numbers of most species might be 2n=2x=32, and the variation of chromosome numbers might be caused by aneuploidy, which had no obvious relationship with the species evolution. This study sheds light on chromosome preparation of Hemiboea and other groups with similar leaf regeneration characteristics, and provides implications for the classification and phylogeny of this group.