Section of Evolutionary Biology, Department of Biology II, University of Munich, Planegg-Martinsried, Germany.
Mol Biol Evol. 2012 Dec;29(12):3641-52. doi: 10.1093/molbev/mss176. Epub 2012 Jul 10.
Abiotic stresses such as drought, extreme temperatures, and salinity have a strong impact on plant adaptation. They act as selective forces on plant physiology and morphology. These selective pressures leave characteristic footprints that can be detected at the DNA sequence level using population genetic tools. On the basis of a candidate gene approach, we investigated signatures of adaptation in two wild tomato species, Solanum peruvianum and S. chilense. These species are native to western South America and constitute a model system for studying adaptation, due to their ability to colonize diverse habitats and the available genetic resources. We have determined the selective forces acting on the C-repeat binding factor (CBF) gene family, which consists of three genes, and is known to be involved in tolerance to abiotic stresses, in particular in cold tolerance. We also analyzed the expression pattern of these genes after drought and cold stresses. We found that CBF3 evolves under very strong purifying selection, CBF2 is under balancing selection in some populations of both species (S. peruvianum/Quicacha and S. chilense/Nazca) maintaining a trans-species polymorphism, and CBF1 is a pseudogene. In contrast to previous studies of cultivated tomatoes showing that only CBF1 was cold induced, we found that all three CBF genes are cold induced in wild tomatoes. All three genes are also drought induced. CBF2 exhibits an allele-specific expression pattern associated with the trans-species polymorphism.
非生物胁迫，如干旱、极端温度和盐度，对植物适应有强烈影响。它们是植物生理学和形态学的选择压力。这些选择压力在 DNA 序列水平上留下了特征性的足迹，可以使用群体遗传学工具来检测。基于候选基因方法，我们研究了两个野生番茄物种（Solanum peruvianum 和 S. chilense）的适应特征。这些物种原产于南美洲西部，是研究适应的理想模式系统，因为它们能够在不同的栖息地中生存，并且具有丰富的遗传资源。我们确定了 CBF 基因家族（由三个基因组成）所受的选择压力，该家族基因已知与非生物胁迫耐受有关，特别是与耐寒性有关。我们还分析了这些基因在干旱和寒冷胁迫后的表达模式。结果发现，CBF3 在非常强烈的纯化选择下进化，CBF2 在两个物种的一些种群（S. peruvianum/Quicacha 和 S. chilense/Nazca）中受到平衡选择，保持了种间多态性，而 CBF1 是一个假基因。与先前对栽培番茄的研究表明只有 CBF1 受低温诱导不同，我们发现所有三个 CBF 基因在野生番茄中都受低温诱导。所有三个基因也都受干旱诱导。CBF2 表现出与种间多态性相关的等位基因特异性表达模式。
