Parallel altitudinal clines reveal trends in adaptive evolution of genome size in Zea mays
Parallel altitudinal clines reveal trends in adaptive evolution of genome size in Zea mays
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DOI：
10.1371/journal.pgen.1007162
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发表时间：
2018-05-01
期刊：
影响因子：
4.5
通讯作者：
Ross-Ibarra, Jeffrey
中科院分区：
文献类型：
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作者：
Bilinski, Paul;Albert, Patrice S.;Ross-Ibarra, Jeffrey
虽然植物中绝大多数基因组大小的差异是由于重复序列的差异，但我们对自然种群中选择如何作用于重复内容知之甚少。本文研究了中美洲和南美洲驯化玉米（Zea mays）地方品种及其野生亲缘大刍动物种内基因组大小和重复序列含量在不同海拔梯度上的平行变化。我们结合基因分型、低覆盖率全基因组序列数据和流式细胞术来检测基因组大小和个体重复丰度选择的证据。我们发现群体结构本身不能解释观察到的变异，这意味着基因组大小的临床模式是由自然选择维持的。我们的模型还提供了对单个异色旋钮重复的选择的证据，可能是由于它们对基因组大小的个体贡献很大。为了更好地理解表型驱动选择对基因组大小的影响，我们对一个基因组大小存在广泛差异的高原大鼠草群体进行了生长室实验。我们发现弱支持基因组大小和细胞大小之间的正相关，但更强的支持基因组大小和细胞生产速率之间的负相关。通过对已发表的玉米茎尖分生组织细胞计数数据的重新分析，我们发现细胞产量与开花时间呈负相关。总之，我们的数据提出了一个模型，在这个模型中，基因组大小的变化是由自然选择驱动的开花时间跨越海拔线，将重复序列的种内变化与适应性表型的重要差异联系起来。
While the vast majority of genome size variation in plants is due to differences in repetitive sequence, we know little about how selection acts on repeat content in natural populations. Here we investigate parallel changes in intraspecific genome size and repeat content of domesticated maize (Zea mays) landraces and their wild relative teosinte across altitudinal gradients in Mesoamerica and South America. We combine genotyping, low coverage whole-genome sequence data, and flow cytometry to test for evidence of selection on genome size and individual repeat abundance. We find that population structure alone cannot explain the observed variation, implying that clinal patterns of genome size are maintained by natural selection. Our modeling additionally provides evidence of selection on individual heterochromatic knob repeats, likely due to their large individual contribution to genome size. To better understand the phenotypes driving selection on genome size, we conducted a growth chamber experiment using a population of highland teosinte exhibiting extensive variation in genome size. We find weak support for a positive correlation between genome size and cell size, but stronger support for a negative correlation between genome size and the rate of cell production. Reanalyzing published data of cell counts in maize shoot apical meristems, we then identify a negative correlation between cell production rate and flowering time. Together, our data suggest a model in which variation in genome size is driven by natural selection on flowering time across altitudinal clines, connecting intraspecific variation in repetitive sequence to important differences in adaptive phenotypes.