Voelckel C, Heenan P B, Janssen B, Reichelt M, Ford K, Hofmann R, Lockhart P J
Allan Wilson Centre for Molecular Ecology and Evolution, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand.
Mol Ecol. 2008 Nov;17(21):4740-53. doi: 10.1111/j.1365-294X.2008.03933.x. Epub 2008 Oct 8.
New Zealand is diverse in alpine and subalpine environments, a consequence of Late Tertiary tectonic and climatic change. However, few studies have sought to evaluate the importance of these environments as abiotic drivers in the diversification of plant species. Of particular interest is the Late Tertiary radiation of Pachycladon, an endemic New Zealand genus of alpine cress. Here we report observations on genome-wide levels of differential expression measured in the habitats of two closely related species of Pachycladon with distinct altitudinal preferences. Using Arabidopsis microarrays, we have identified 310 predominantly hormone- and stress-response genes up-regulated in Pachycladon fastigiata and 324 genes up-regulated in Pachycladon enysii. Expression patterns for glucosinolate biosynthesis and hydrolysis genes (MAM1, MAM-I, MAM-D, AOP2, ESP, ESM1) as well as flavonoid biosynthesis genes (F3'H, FLS, FAH1) were found to be species specific. Predicted differences in flavonoid contents were partly confirmed by high performance liquid chromatography analysis. Differences in glucosinolate profiles and glucosinolate hydrolysis products obtained by high performance liquid chromatography and gas chromatography-mass spectrometry analysis, respectively, also supported inferences from expression analyses. Five glucosinolate chemotypes were matched to known Arabidopsis ecotypes, and the potential adaptive significance of these chemotypes has been discussed. Our findings, in contrast to expectations for evolution of the New Zealand flora, suggest that biotic drivers, such as plant-herbivore interactions, are likely to be as important as abiotic drivers in the diversification of Pachycladon.
新西兰的高山和亚高山环境多样，这是第三纪晚期构造和气候变化的结果。然而，很少有研究试图评估这些环境作为非生物驱动因素在植物物种多样化中的重要性。特别令人感兴趣的是厚叶草属（Pachycladon）的第三纪晚期辐射，厚叶草属是新西兰特有的高山水芹属。在此，我们报告了在两种具有不同海拔偏好的厚叶草属近缘物种的栖息地中测得的全基因组水平差异表达的观察结果。使用拟南芥微阵列，我们鉴定出在紧密厚叶草（Pachycladon fastigiata）中上调的310个主要与激素和应激反应相关的基因，以及在恩氏厚叶草（Pachycladon enysii）中上调的324个基因。发现硫代葡萄糖苷生物合成和水解基因（MAM1、MAM-I、MAM-D、AOP2、ESP、ESM1）以及类黄酮生物合成基因（F3'H、FLS、FAH1）的表达模式具有物种特异性。高效液相色谱分析部分证实了预测的类黄酮含量差异。分别通过高效液相色谱和气相色谱-质谱分析获得的硫代葡萄糖苷谱和硫代葡萄糖苷水解产物的差异，也支持了表达分析的推断。五种硫代葡萄糖苷化学型与已知的拟南芥生态型相匹配，并讨论了这些化学型的潜在适应性意义。与对新西兰植物群进化的预期相反，我们的研究结果表明，生物驱动因素，如植物与食草动物的相互作用，在厚叶草属的多样化中可能与非生物驱动因素同样重要。
