Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, Brno, CZ, 61137, Czech Republic.
Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná 5, Prague, CZ, 12844, Czech Republic.
Am J Bot. 2020 Sep;107(9):1253-1259. doi: 10.1002/ajb2.1526. Epub 2020 Sep 3.
As repeatedly shown, the remarkable variation in the genome size of angiosperms can be shaped by extrinsic selective pressures, including nutrient availability. Carnivory has evolved independently in 10 angiosperm clades, but all carnivorous plants share a common affinity to nutrient-poor habitats. As such, carnivory and genome reduction could be responses to the same environmental pressure. Indeed, the smallest genomes among flowering plants are found in the carnivorous family Lentibulariaceae, where a unique mutation in cytochrome c oxidase (COX) is suspected to promote genome miniaturization. Despite these hypotheses, a phylogenetically informed test of genome size and nutrient availability across carnivorous clades has so far been missing.
Using linear mixed models, we compared genome sizes of 127 carnivorous plants from 7 diverse angiosperm clades with 1072 of their noncarnivorous relatives. We also tested whether genome size in Lentibulariaceae reflects the presence of the COX mutation.
The genome sizes of carnivorous plants do not differ significantly from those of their noncarnivorous relatives. Based on available data, no significant association between the COX mutation and genome miniaturization could be confirmed, not even when considering polyploidy.
Carnivory alone does not seem to significantly affect genome size decrease. Plausibly, it might actually counterbalance the effect of nutrient limitation on genome size evolution. The role of the COX mutation in genome miniaturization needs to be evaluated by analysis of a broader data set because current knowledge of its presence across Lentibulariaceae covers less than 10% of the species diversity in this family.
正如反复表明的那样，被子植物基因组大小的显著变化可以通过外在的选择压力来塑造，包括养分的可利用性。肉食性已在 10 个被子植物类群中独立进化，但所有肉食植物都有一个共同的特点，即它们喜欢养分贫瘠的栖息地。因此，肉食性和基因组减少可能是对相同环境压力的反应。事实上，在食虫植物科中可以发现开花植物中最小的基因组，在那里，细胞色素 c 氧化酶 (COX) 的一个独特突变被怀疑促进了基因组的小型化。尽管有这些假说，但迄今为止，在肉食性类群中还没有进行过基于系统发育的基因组大小与养分可利用性的测试。
我们使用线性混合模型，比较了来自 7 个不同被子植物类群的 127 种肉食植物与 1072 种非肉食植物的亲缘关系的基因组大小。我们还测试了 Lentibulariaceae 中的 COX 突变是否反映了基因组的小型化。
肉食植物的基因组大小与非肉食植物的亲缘关系没有显著差异。根据现有数据，无法确认 COX 突变与基因组小型化之间存在显著的关联，即使考虑到多倍体也是如此。
单独的肉食性似乎不会显著影响基因组大小的减少。合理地说，它实际上可能会抵消营养限制对基因组大小进化的影响。COX 突变在基因组小型化中的作用需要通过更广泛的数据集来评估，因为目前对它在 Lentibulariaceae 中的存在的了解仅涵盖了该科物种多样性的不到 10%。
