Liu Xinyan, Gao Shuai, Cheng Aixia, Lou Hongxiang
Department of Pharmacy, Qilu Hospital of Shandong University, Jinan, 250012, Shandong, China.
Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan, 250012, Shandong, China.
Planta. 2025 Jan 9;261(2):28. doi: 10.1007/s00425-024-04602-z.
The evolutionary conservation of type III polyketide synthases (PKS) in Selaginella has been elucidated, and the critical amino acid residues of the anther-specific chalcone synthase-like enzyme (SmASCL) have been identified. Selaginella species are the oldest known vascular plants and a valuable resource for the study of metabolic evolution in land plants. Polyketides, especially flavonoids and sporopollenin precursors, are essential prerequisites for plant land colonization. Although type III polyketide synthases (PKS) are widely studied in seed plants, the related enzymes in Selaginella remain poorly characterized. Here, eight type III PKSs were identified in the Selaginella moellendorffii genome and classified into three clusters. Two PKSs were selected for further research based on their phylogenetic relationships and protein sequence similarity. Functional studies revealed that they were chalcone synthase (SmCHS) and anther-specific CHS-like enzyme (SmASCL). These enzymes are involved in the biosynthesis of flavonoids and sporopollenin, respectively. Their sequence information and enzymatic activity are similar to the orthologs in other plants. Phylogenetic analysis revealed that the ASCL and CHS enzymes were separated into two clades from the Bryophyta. These results suggest that CHS and ASCL emerged in the first land plants and then remained conserved during plant evolution. To study the structural basis of the enzymatic function of SmASCL, a series of mutants were constructed. The number of condensation reactions catalyzed by the P210L/Y211D and I200V/G201T double mutants exceeds that of the wild-type enzyme. Our study provides insight into the characteristics and functions of type III PKSs in S. moellendorffii. It also offers clues for a deeper understanding of the relationship between active sites and the enzymatic function of ASCLs.
已阐明卷柏中III型聚酮合酶（PKS）的进化保守性，并鉴定了花药特异性查尔酮合酶样酶（SmASCL）的关键氨基酸残基。卷柏是已知最古老的维管植物，是研究陆地植物代谢进化的宝贵资源。聚酮化合物，尤其是黄酮类化合物和孢粉素前体，是植物在陆地上定殖的必要前提条件。尽管III型聚酮合酶（PKS）在种子植物中得到了广泛研究，但卷柏中的相关酶仍未得到充分表征。在此，在卷柏基因组中鉴定出8种III型PKS，并分为三个簇。基于它们的系统发育关系和蛋白质序列相似性，选择了两种PKS进行进一步研究。功能研究表明，它们分别是查尔酮合酶（SmCHS）和花药特异性CHS样酶（SmASCL）。这些酶分别参与黄酮类化合物和孢粉素的生物合成。它们的序列信息和酶活性与其他植物中的直系同源物相似。系统发育分析表明，ASCL和CHS酶从苔藓植物中分为两个进化枝。这些结果表明，CHS和ASCL在第一批陆地植物中出现，然后在植物进化过程中保持保守。为了研究SmASCL酶功能的结构基础，构建了一系列突变体。P210L/Y211D和I200V/G201T双突变体催化的缩合反应数量超过野生型酶。我们的研究深入了解了卷柏中III型PKS的特征和功能。它还为更深入理解ASCLs的活性位点与酶功能之间的关系提供了线索。
