Hendrix Bill, Stewart James McD
University of Arkansas, 115 Plant Science Building, Fayetteville, AR 72701, USA.
Ann Bot. 2005 Apr;95(5):789-97. doi: 10.1093/aob/mci078. Epub 2005 Feb 8.
Gossypium is an economically important, globally distributed taxon comprising more than 50 species. DNA content estimates from about half of the species indicate over a 3-fold variation exists. However, the nine DNA content estimates for G. hirsutum reveal over a 2-fold difference for this species alone. Recent reports have shown that several plant compounds can bias DNA content estimates obtained by commonly used methods. The purpose of this research was to examine the standardization procedures used for DNA content determinations with flow cytometry as applied to Gossypium, and generate revised DNA content estimates for all available Gossypium species using best-standard practices.
Flow cytometry was used to measure fluorescence of isolated Gossypium nuclei stained with propidium iodide. Fluorescence values were converted to DNA content estimates based on the nuclear fluorescence of standard genotypes of barley, corn and rice. Various combinations of nuclei preparations relative to the standards were evaluated for their influence on the estimates.
Both external standardization and internal standardization with Oryza sativa 'IR36' yielded statistically similar DNA content estimates for Gossypium. Internal standardization with Hordeum vulgare 'Sultan' resulted in a high estimate of DNA content. Nuclear DNA content estimates were generated for 37 Gossypium species using external standardization. Estimates of ancestral genome sizes reveal that both increases and decreases in nuclear DNA content have occurred. Variation in intraspecific and intragenomic DNA content was low, and the allopolyploid AD-genome size was nearly the additive of its progenitor genomes.
Due to unknown factors, internal standardization with H. vulgare 'Sultan' may not be appropriate for DNA content determinations of Gossypium. The current DNA content estimates support accepted cytogenetic divisions of the genus. Gossypium is a genus that exhibits genome constancy both through speciation within genomic groups and allopolyploidization.
棉属是一个具有重要经济价值、分布于全球的分类群，包含50多个物种。约一半物种的DNA含量估计表明存在超过3倍的差异。然而，仅陆地棉的9个DNA含量估计就显示出该物种存在超过2倍的差异。最近的报告表明，几种植物化合物会使常用方法获得的DNA含量估计产生偏差。本研究的目的是检验用于棉属植物DNA含量测定的流式细胞术标准化程序，并使用最佳标准方法为所有可用的棉属物种生成修订后的DNA含量估计值。
使用流式细胞术测量用碘化丙啶染色的分离棉属细胞核的荧光。基于大麦、玉米和水稻标准基因型的核荧光，将荧光值转换为DNA含量估计值。评估了相对于标准的细胞核制备的各种组合对估计值的影响。
使用水稻‘IR36’进行外部标准化和内部标准化，对棉属植物的DNA含量估计在统计学上相似。使用大麦‘苏丹’进行内部标准化导致DNA含量估计值偏高。使用外部标准化为37个棉属物种生成了核DNA含量估计值。祖先基因组大小的估计表明，核DNA含量既有增加也有减少。种内和基因组内DNA含量的变异较低，异源多倍体AD基因组大小几乎是其祖先基因组大小的加和。
由于未知因素，使用大麦‘苏丹’进行内部标准化可能不适用于棉属植物的DNA含量测定。当前的DNA含量估计支持该属公认的细胞遗传学分类。棉属是一个通过基因组组内的物种形成和异源多倍体化都表现出基因组稳定性的属。
