CHROMOSOME BEHAVIOR AT THE BASE OF THE ANGIOSPERM RADIATION: KARYOLOGY OF TRITHURIA SUBMERSA (HYDATELLACEAE, NYMPHAEALES)
CHROMOSOME BEHAVIOR AT THE BASE OF THE ANGIOSPERM RADIATION: KARYOLOGY OF TRITHURIA SUBMERSA (HYDATELLACEAE, NYMPHAEALES)
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DOI：
10.3732/ajb.1400050
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发表时间：
2014-09-01
影响因子：
3
通讯作者：
Rudall, Paula J.
中科院分区：
文献类型：
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作者：
Kynast, Ralf G.;Joseph, Jeffrey A.;Rudall, Paula J.
研究前提：海枣科是一种微小的一年生草本植物，具有研究被子植物早期进化的模式系统的潜力，但其核型和倍性水平几乎是未知的。我们调查了这些方面的Trithuria summosa，一个广泛的物种，我们表明是适合扩大营养繁殖。通过对培养条件的开发和优化，我们使用流式细胞术估计基因组大小，使用Feulgen染色后的根分生组织南瓜计数染色体数目，并使用小孢子母细胞检查减数分裂染色体行为。在1/2 MS培养基上，添加维生素和2%蔗糖，用0.7%琼脂固化，在临界光温条件下进行无性繁殖。幼苗生长需要培养基中补充活性炭。T. 2C = 2.74 pg（与2.68 Gbp相似）。孢子体染色体数目为2n = 56，具有双峰互补，这可能表明异源多倍体起源。一些最大的染色体缺乏可识别的收缩，这与非常不寻常和不规则的染色体行为有关。小孢子母细胞减数分裂减少和不同步，表现出修改的中间细胞分裂与核分裂分数postreduction，表明部分倒置的小孢子发生。为研究早期分歧被子植物提供了新的机会。显着不同的减数分裂行为展示了一个潜在的祖先小孢子发生的新见解。
Premise of the study: Hydatellaceae are minute annual herbs with potential as a model system for studying early angiosperm evolution, but their karyology and ploidy levels are almost unknown. We investigated these aspects of Trithuria submersa, a widespread species that we show to be amenable to extended vegetative propagation.Methods: We cultivated plants of T. submersa in vitro after developing and optimizing culture conditions. We estimated genome size using flow cytometry, counted chromosome numbers using root-meristem squashes after Feulgen staining, and examined meiotic chromosome behavior using microsporocytes.Key results: We developed methods to reliably germinate seeds of T. submersa and to propagate them vegetatively in critical thermo-and photoperiod regimes on 1/2 Murashige-Skoog (MS) medium with vitamins and 2% sucrose solidified with 0.7% agar-agar. Seedling growth requires the medium be supplemented with activated charcoal. The mean nuclear DNA content of T. submersa sporophytes is 2C = 2.74 pg (similar to 2.68 Gbp). The sporophytic chromosome number is 2n = 56 with a bimodal complement, which may suggest an allopolyploid origin. Some of the largest chromosomes lack a recognizable constriction, which relates to a highly unusual and irregular chromosome behavior. Microsporocytes undergo reduced and asynchronous meioses that show a modified intermediate cell division with a nucleus division by fractional postreduction, indicating partially inverted microsporogenesis.Conclusions: In vitro cultivation and karyological assessment of T. submersa open new opportunities for investigating early-divergent angiosperms. The remarkably different meiotic behavior exhibits new insights into a potentially ancestral microsporogenesis.