Plant Cell:亚细胞重定位和正选择在杨树重复基因保留中的作用

摘要 : 中科院植物研究所曾庆银研究组以杨树三型氧化酶(PRX)基因家族为例，揭示了亚细胞定位的分化和正选择在杨树基因家族功能分化中扮演着的重要角色。相关文章发表于近期的《The Plant Cell》杂志上。

图.杨树PRX蛋白的结构及亚细胞定位的分化

杨树基因组中大部分基因家族组成庞大，众多家族成员如何能在长期的演化历程中被保留下来?其家族内成员间的功能分化机制又是什么?这些科学问题目前还未得到明确回答。中科院植物研究所曾庆银研究组以杨树三型氧化酶(PRX)基因家族为例来回答这一系列科学问题。

PRX基因家族在木质素生物合成和抗逆反应中发挥重要作用。研究发现，杨树基因组中有两组串联重复的PRX基因，其祖先基因编码的蛋白定位在细胞壁上。在其后的演化历程中，有一个祖先拷贝获得液泡定位的信号肽而定位在液泡中，然后液泡PRX基因经历了快速的扩张，扩张后的液泡PRX基因受到正选择驱动而导致所编码蛋白的生化功能发生分化。

研究揭示了亚细胞定位的分化和正选择在杨树基因家族功能分化中扮演着的重要角色。研究结果已在The Plant Cell期刊上发表。

同时，The plant Cell期刊将该成果选为研究亮点，并做了题为“When to hold them: Retention of duplicate genes in poplar”(Jennifer Mach, 2014, 26: 2283)的点评，评述了蛋白质亚细胞定位的变化和正选择在杨树重复基因保留中的作用机制。研究成果也入选了FACULTY of 1000，被推荐为本领域有重要进展的文献(http://f1000.com/prime/718453323)。

原文摘要：

Subcellular Relocalization and Positive Selection Play Key Roles in the Retention of Duplicate Genes ofPopulus Class III Peroxidase Family

Lin-Ling Ren, Yan-Jing Liu, Hai-Jing Liu, Ting-Ting Qian, Li-Wang Qi, Xiao-Ru Wang and Qing-Yin Zeng

Gene duplication is the primary source of new genes and novel functions. Over the course of evolution, many duplicate genes lose their function and are eventually removed by deletion. However, some duplicates have persisted and evolved diverse functions. A particular challenge is to understand how this diversity arises and whether positive selection plays a role. In this study, we reconstructed the evolutionary history of the class III peroxidase (PRX) genes from the Populus trichocarpa genome. PRXs are plant-specific enzymes that play important roles in cell wall metabolism and in response to biotic and abiotic stresses. We found that two large tandem-arrayed clusters of PRXs evolved from an ancestral cell wall type PRX to vacuole type, followed by tandem duplications and subsequent functional specification. Substitution models identified seven positively selected sites in the vacuole PRXs. These positively selected sites showed significant effects on the biochemical functions of the enzymes. We also found that positive selection acts more frequently on residues adjacent to, rather than directly at, a critical active site of the enzyme, and on flexible regions rather than on rigid structural elements of the protein. Our study provides new insights into the adaptive molecular evolution of plant enzyme families.

作者：植物所

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