植物查尔酮合成酶超基因家族的分子进化

Molecular Evolution of Chalcone Synthase Gene Superfamily in Plants

查尔酮合成酶(CHS)超基因家族又称为植物类型III聚酮合酶超基因家族,其编码酶通过催化和合成一系列结构多样及生理活性各异的次生代谢物,在植物生长发育和适应环境的过程中扮演着重要角色。为全面了解CHS超基因家族在植物中的进化规律,重建其进化历史,该研究利用14种具有全基因组数据的代表植物,通过生物信息学手段,深入挖掘和分析了不同植物类群基因组中查尔酮合成酶超基因家族的成员构成,推测了其可能的扩增机制和功能分歧,并探讨了该超基因家族在植物中的总体进化趋势。结果共识别144条具有表达信息的同源序列,它们全部来自9种陆生植物的基因组,藻类植物基因组中没有发现相关序列。系统发育和进化分析表明,CHS超基因家族的起源古老,它们可能为适应复杂的生态环境而出现在早期的陆生植物中,之后在长期的进化过程中不断发生谱系的特异扩张和拷贝丢失,最后通过功能分歧的形式在不同植物类群中被分别固定。此外,进化检验也显示,尽管CHS超基因家族内部发生了多样的遗传改变,但整个超基因家族仍处于强烈的纯化选择之下,并且个体基因中也无任何单氨基酸位点受到正向选择的影响。

The chalcone synthase （CHS） gene superfamily, also known as plant-specific type III polyketide synthase gene superfamily, encodes many important enzymes that can catalyze and synthesize various plant secondary metabo- lites with diverse structures and different biological activities. These metabolites play key roles in plant growth, reproduc- tion, and plant adaptation to the environment. To fully understand the basic evolutionary rules of the CHS gene super- family in plants and reconstruct its evolutionary history, we performed bioinformatics analysis of CHS genes in 14 plant species with whole-genome data. We performed a BLAST search to identify the gene members of the CHS superfamily. The possible expansion mechanisms and functional divergences of the members were characterized, and the evolution- ary trend of the superfamily was explored. We identified 144 genes with expression information; all are expressed in 9 land plants but not 5 algae. Phylogenetic analysis revealed that the CHS gene superfamily had an ancient origin and complicated evolutionary history. It probably appeared in early terrestrial plants to adapt to the complex environment, then experienced lineage-specific expansions or gene loss during evolution, and finally was fixed in different plant taxa through functional divergences. In addition, evolutionary testing showed that despite diverse genetic differentiation within the CHS superfamily, the whole superfamily was still filtered by strong purifying selection and no single amino acid site within an individual gene was affected by positive selection.