Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309.
Laboratory of Molecular Evolution, Department of Genetics, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, 91501, Brazil.
Evolution. 2018 Dec;72(12):2792-2802. doi: 10.1111/evo.13589. Epub 2018 Sep 19.
Developmental pathways play a major role in influencing the distribution of naturally occurring phenotypes. For example, pathway structure and regulation could make some phenotypes inaccessible or restrict the routes through which phenotypes evolve. In this study, we examine floral anthocyanin pigments across the Solanaceae family and test whether patterns of phenotypic variation are consistent with predicted constraints based on the structure of the flavonoid biosynthetic pathway. We find that anthocyanin evolution occurs in a stepwise manner whereby transitions between the production of red mono hydroxylated pelargonidin pigments and blue trihydroxylated delphinidin pigments first passes through an intermediate step of producing purple dihydroxylated cyanidin pigments. Although the transitions between these three pigment types differ in frequency, we infer that these shifts are often reversible, suggesting that the functionality of the underlying biochemical pathway is generally conserved. Furthermore, our study finds that some pigment combinations are never observed, pointing to additional constraints on naturally occurring phenotypes. Overall, our findings provide insights into how the structure of an angiosperm-wide biochemical pathway has shaped macroevolutionary variation in floral pigmentation.
发育途径在影响自然发生的表型分布方面起着重要作用。例如，途径结构和调节可能使某些表型无法获得或限制表型进化的途径。在这项研究中，我们检查了茄科植物家族的花色素，并测试了表型变异模式是否与基于类黄酮生物合成途径结构的预测限制一致。我们发现花色素的进化是逐步发生的，红色单羟基化的天竺葵色素和蓝色三羟基化的飞燕草色素之间的转化首先通过产生紫色二羟基化的矢车菊色素的中间步骤进行。尽管这三种色素类型之间的转化频率不同，但我们推断这些转变通常是可逆的，这表明潜在生化途径的功能通常是保守的。此外，我们的研究发现，有些色素组合从未被观察到，这表明对自然发生的表型存在额外的限制。总的来说，我们的研究结果提供了关于被子植物广泛生化途径的结构如何塑造花色素宏观进化变异的深入了解。
