Salmela Matti J, Greenham Kathleen, Lou Ping, McClung C Robertson, Ewers Brent E, Weinig Cynthia
Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.
Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA.
Plant Cell Environ. 2016 Jun;39(6):1293-303. doi: 10.1111/pce.12670. Epub 2016 Feb 13.
Circadian clocks have evolved independently in all three domains of life, and fitness benefits of a functional clock have been demonstrated in experimental genotypes in controlled conditions. Still, little is known about genetic variation in the clock and its fitness consequences in natural populations from heterogeneous environments. Using Wyoming populations of the Arabidopsis relative Boechera stricta as our study system, we demonstrate that genetic variation in the clock can occur at multiple levels: means of circadian period among populations sampled at different elevations differed by less than 1 h, but means among families sampled within populations varied by as much as 3.5 h. Growth traits also varied among and within populations. Within the population with the most circadian variation, we observed evidence for a positive correlation between period and growth and a negative correlation between period and root-to-shoot ratio. We then tested whether performance tradeoffs existed among families of this population across simulated seasonal settings. Growth rankings of families were similar across seasonal environments, but for root-to-shoot ratio, genotype × environment interactions contributed significantly to total variation. Therefore, further experiments are needed to identify evolutionary mechanisms that preserve substantial quantitative genetic diversity in the clock in this and other species.
生物钟在生命的所有三个域中独立进化，并且在受控条件下的实验基因型中已证明了功能性生物钟对适应性的益处。然而，对于生物钟的遗传变异及其在异质环境中的自然种群中的适应性后果，我们仍然知之甚少。以拟南芥近缘种窄叶博落回的怀俄明种群作为我们的研究系统，我们证明生物钟的遗传变异可以在多个水平上发生：在不同海拔采集的种群之间，昼夜节律周期的平均值差异小于1小时，但在种群内采集的家系之间，平均值差异高达3.5小时。生长性状在种群间和种群内也存在差异。在昼夜节律变化最大的种群中，我们观察到周期与生长之间存在正相关，周期与根冠比之间存在负相关。然后，我们测试了该种群的家系在模拟季节性环境中是否存在性能权衡。家系的生长排名在不同季节环境中相似，但对于根冠比，基因型×环境互作对总变异有显著贡献。因此，需要进一步的实验来确定在该物种和其他物种中维持生物钟中大量数量遗传多样性的进化机制。
