Allaby Robin G, Peterson Gregory W, Merriwether David Andrew, Fu Yong-Bi
Department of Anthropology, Binghamton University SUNY, Binghamton, NY 13902, USA.
Theor Appl Genet. 2005 Dec;112(1):58-65. doi: 10.1007/s00122-005-0103-3. Epub 2005 Oct 8.
A phylogenetic analysis was conducted on 34 alleles of 2.5 kb sized stearoyl-ACP desaturase II (sad2), obtained from 30 accessions of cultivated and pale flax (Linum spp.), to elucidate the history of flax domestication. The analysis supports a single domestication origin for extant cultivated flax. The phylogenetic evidence indicates that flax was first domesticated for oil, rather than fibre. The genetic diversity of the sad2 locus in cultivated flax is low when compared to that of the pale flax assayed. An absolute archaeological date could be applied to the synonymous substitution rate of sad2 in cultivated flax, yielding a high estimate of 1.60-1.71x10(-7) substitutions/site/year. The occurrence of nonsynonymous substitutions at conserved positions of the third exon in alleles from cultivated flax suggests that the locus may have been subjected to an artificial selection pressure. The elevated synonymous substitution rate is also compatible with a population expansion of flax since domestication, followed by a population decline in historic times. These findings provide new insight into flax domestication and are significant for the continuous exploration of the flax germplasm for utilization.
对从30份栽培亚麻和野生亚麻（亚麻属）材料中获得的大小为2.5 kb的硬脂酰-ACP去饱和酶II（sad2）的34个等位基因进行了系统发育分析，以阐明亚麻的驯化历史。该分析支持现存栽培亚麻有单一的驯化起源。系统发育证据表明，亚麻最初是为了获取油而不是纤维被驯化的。与所检测的野生亚麻相比，栽培亚麻中sad2基因座的遗传多样性较低。可以将一个绝对考古日期应用于栽培亚麻中sad2的同义替换率，得出的估计值很高，为1.60 - 1.71×10⁻⁷替换/位点/年。栽培亚麻等位基因第三个外显子保守位置上非同义替换的出现表明该基因座可能受到了人工选择压力。升高的同义替换率也与亚麻自驯化以来的种群扩张，随后在历史时期种群数量下降相一致。这些发现为亚麻驯化提供了新的见解，对于持续探索亚麻种质资源以供利用具有重要意义。
