Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):14360-5. doi: 10.1073/pnas.1104853108. Epub 2011 Aug 15.
Phylogenetic analyses of genes with demonstrated involvement in evolutionary transitions can be an important means of resolving conflicting hypotheses about evolutionary history or process. In sunflower, two genes have previously been shown to have experienced selective sweeps during its early domestication. In the present study, we identified a third candidate early domestication gene and conducted haplotype analyses of all three genes to address a recent, controversial hypothesis about the origin of cultivated sunflower. Although the scientific consensus had long been that sunflower was domesticated once in eastern North America, the discovery of pre-Columbian sunflower remains at archaeological sites in Mexico led to the proposal of a second domestication center in southern Mexico. Previous molecular studies with neutral markers were consistent with the former hypothesis. However, only two indigenous Mexican cultivars were included in these studies, and their provenance and genetic purity have been questioned. Therefore, we sequenced regions of the three candidate domestication genes containing SNPs diagnostic for domestication from large, newly collected samples of Mexican sunflower landraces and Mexican wild populations from a broad geographic range. The new germplasm also was genotyped for 12 microsatellite loci. Our evidence from multiple evolutionarily important loci and from neutral markers supports a single domestication event for extant cultivated sunflower in eastern North America.
进化转变相关基因的系统发育分析可以成为解决进化历史或过程中冲突假说的重要手段。在向日葵中，以前已经有两个基因在其早期驯化过程中经历了选择清除。在本研究中，我们鉴定了第三个候选早期驯化基因，并对所有三个基因进行了单倍型分析，以解决有关栽培向日葵起源的一个最近备受争议的假说。尽管科学界长期以来一直认为向日葵在北美东部被驯化了一次，但在墨西哥的考古遗址中发现了哥伦布前的向日葵遗骸，这导致了在墨西哥南部存在第二个驯化中心的假说。以前使用中性标记进行的分子研究与前者的假说一致。然而，这些研究仅包括两种墨西哥本土品种，并且其起源和遗传纯度一直受到质疑。因此，我们从广泛地理范围内的新收集的墨西哥向日葵地方品种和墨西哥野生种群中，对包含驯化 SNP 的三个候选驯化基因的区域进行了测序。新的种质资源还针对 12 个微卫星标记进行了基因型分析。我们来自多个进化重要基因座和中性标记的证据支持现有的栽培向日葵在北美东部经历了一次单一的驯化事件。
