红砂基因组大小变异及物种分化

Genome size variations and species differentiation of Reaumuria soongarica

红砂(Reaurnuria soongarica,柽柳科)是广泛分布于亚洲内陆干旱区温带荒漠的建群灌木,该物种内部经历过分化和杂交事件,是研究荒漠植物多样性发生和杂交物种形成的理想模型。然而,红砂不同群体的倍性水平尚不清楚,制约了对其物种形成机制的深入研究。为了确定红砂不同支系的倍性及基因组大小变异模式,本研究以红砂幼苗根尖为实验材料,以野生番茄(Solanum pimpine llifolium)作为内标物种,利用流式细胞术对分别来自北疆支系及其可能的亲本支系(东部和西部支系)的共8个红砂群体进行了DNA 1C-值测定和分析。结果显示:红砂东部支系的DNA 1C-值(1.149±0.012 pg)略小于西部支系的1C-值(1.195±0.031 pg)。北疆支系中阜康(FK)和沙湾(SW)群体的DNA 1C-值处于东、西支系的1C-值之间,而火烧山(HSS)和五彩城(WCC)群体的1C-值接近东、西支系1C-值的2倍。结合之前的分子标记结果,我们推测北疆支系中阜康和沙湾群体为东、西部支系的同倍体杂交种群,而火烧山和五彩城群体属于异源四倍体杂交种群。不同倍性的北疆群体起源于不同的杂交事件,可以划归为不同的物种。

Aims:As a constructive shrub species widely distributed across the temperate deserts of arid Central Asia,Reaumuria soongarica(Tamaricaceae)had undergone divergence and hybridization during its evolutionary history,which make it an ideal model for understanding the molecular basis of biodiversity of desert ecosystems and plant hybrid speciation.However,the ploidy level of different populations of R.soongarica is still unclear,which confines the further study on its speciation mechanism.Methods:To clarify the ploidy level and variation patterns of genome size of different R.soongarica lineages,we investigated the DNA 1 C-value of eight R.soongarica populations from the northern lineage(distributed in northern Xinjiang)and its putative parental lineages(the eastern and western lineages)by flow cytometry.The young roots of R.soongarica were selected as the experimental material,and Solanum pimpinellifolium was used as an internal standard species.Results:Our data showed that the DNA 1 C-value of the eastern lineage(1.149±0.012 pg)was slightly smaller than that of the western lineage(1.195±0.031 pg),and the DNA 1 C-value of the Fukang(FW)and Shawan(SW)populations in the northern lineage was intermediate between that of its parental lineages.However,the DNA 1 C-values of the Huoshaoshan(HSS)and Wucaicheng(WCC)populations from the northern lineage were closely twice as those from the eastern and western populations.Conclusion:Considering to the previous results of molecular markers,we infer that the FW and SW populations belong to the homoploid hybrid populations from the eastern and western lineages,while the HSS and WCC populations are allopolyploid hybrid populations.The populations with different ploidy levels in the northern lineage could originate from different hybrid events,which could be classified into different species.