Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA.
BMC Genomics. 2012 Nov 20;13:641. doi: 10.1186/1471-2164-13-641.
Polyadenylation, an essential step in eukaryotic gene expression, requires both cis-elements and a plethora of trans-acting polyadenylation factors. The polyadenylation factors are largely conserved across mammals and fungi. The conservation seems also extended to plants based on the analyses of Arabidopsis polyadenylation factors. To extend this observation, we systemically identified the orthologs of yeast and human polyadenylation factors from 10 plant species chosen based on both the availability of their genome sequences and their positions in the evolutionary tree, which render them representatives of different plant lineages.
The evolutionary trajectories revealed several interesting features of plant polyadenylation factors. First, the number of genes encoding plant polyadenylation factors was clearly increased from "lower" to "higher" plants. Second, the gene expansion in higher plants was biased to some polyadenylation factors, particularly those involved in RNA binding. Finally, while there are clear commonalities, the differences in the polyadenylation apparatus were obvious across different species, suggesting an ongoing process of evolutionary change. These features lead to a model in which the plant polyadenylation complex consists of a conserved core, which is rather rigid in terms of evolutionary conservation, and a panoply of peripheral subunits, which are less conserved and associated with the core in various combinations, forming a collection of somewhat distinct complex assemblies.
The multiple forms of plant polyadenylation complex, together with the diversified polyA signals may explain the intensive alternative polyadenylation (APA) and its regulatory role in biological functions of higher plants.
多聚腺苷酸化是真核生物基因表达的一个必要步骤，需要顺式元件和大量的反式作用多聚腺苷酸化因子。多聚腺苷酸化因子在哺乳动物和真菌中是高度保守的。基于拟南芥多聚腺苷酸化因子的分析，这种保守性似乎也扩展到了植物。为了扩展这一观察结果，我们系统地从 10 种植物中鉴定了酵母和人类多聚腺苷酸化因子的同源物，这些植物是根据它们的基因组序列的可用性及其在进化树上的位置选择的，这使它们成为不同植物谱系的代表。
进化轨迹揭示了植物多聚腺苷酸化因子的几个有趣特征。首先，编码植物多聚腺苷酸化因子的基因数量显然从“低等”植物增加到“高等”植物。其次，高等植物的基因扩张偏向于某些多聚腺苷酸化因子，特别是那些参与 RNA 结合的因子。最后，尽管有明显的共性，但不同物种之间的多聚腺苷酸化装置的差异是明显的，这表明进化变化仍在继续。这些特征导致了一个模型，即植物多聚腺苷酸化复合物由一个保守的核心组成，这个核心在进化保守性方面是相当僵化的，而一系列外围亚基则不太保守，与核心以各种组合结合在一起，形成了一系列略有不同的复合物组装体。
植物多聚腺苷酸化复合物的多种形式，以及多样化的 polyA 信号，可能解释了高等植物中密集的选择性多聚腺苷酸化（APA）及其在生物学功能中的调控作用。
