Functional and structural profiles of GST gene family from three Populus species reveal the sequence-function decoupling of orthologous genes

First author: Qi Yang; Affiliations: State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry (中国林科院林木遗传育种国家重点实验室): Beijing, China

Corresponding author: Qing‐Yin Zeng(曾庆银)

A common assumption in comparative genomics is that orthologous genes are functionally more similar than paralogous genes. However, the validity (正确性) of this assumption needs to be assessed using robust experimental data. We conducted tissue‐specific gene expression and protein function analyses of orthologous groups within the glutathione S‐ ransferase (GST; 谷胱甘肽S-转移酶) gene family in three closely related Populus species: Populus trichocarpa (毛果杨), Populus euphratica (胡杨) and Populus yatungensis (亚东杨). This study identified 21 GST orthologous groups in the three Populus species. Although the sequences of the GST orthologous groups were highly conserved, the divergence in enzymatic functions was prevalent. Through site‐directed mutagenesis of orthologous proteins, this study revealed that nonsynonymous substitutions at key amino acid sites played an important role in the divergence of enzymatic functions. In particular, a single amino acid mutation (Arg39→Trp39) contributed to P. euphratica PeGSTU30 possessing high enzymatic activity via increasing the hydrophobicity (疏水性) of the active cavity (活性腔). This study provided experimental evidence showing that orthologues belonging to the gene family have functional divergences. The nonsynonymous substitutions at a few amino acid sites resulted in functional divergence of the orthologous genes. Our findings provide new insights into the evolution of orthologous genes in closely related species.

比较基因组学通常的一个假设就是直系同源基因要比旁系同源基因在功能上更加保守。然而，该假设的正确性需要通过扎实的试验数据来验证。本文对三个近缘杨树物种（毛果杨、胡杨和亚东杨）的谷胱甘肽S-转移酶（GST）基因家族的直系同源基因进行组织特异性基因表达和蛋白功能分析。作者共鉴定了21个GST直系同源组。尽管在GST直系同源组中不同直系同源基因的序列非常的保守，但其在酶功能上的分化普遍存在。通过对直系同源蛋白位点直接诱变的方法，试验结果显示在关键氨基酸的非同义位点的突变通常会导致酶功能的分化。比如说，胡杨PeGSTU30蛋白上第39号精氨酸变为色氨酸后，由于蛋白活性腔疏水性的增加，极大的增加了该蛋白的酶活性。本文的研究通过试验证据说明了同一个基因家族的直系同源基因存在功能分化。在少数几个关键氨基酸位点的非同义替换就可能会导致直系同源基因的功能分化。本文的研究结果为近缘物种间直系同源基因的演化提供了新的视野。

通讯：曾庆银（http://www.lseb.cn/zengqingyin）

个人简介：1998年，吉林大学生命科学学院，生物化学学士；2002年，吉林大学生命科学学院，微生物与生化药学硕士；2006年，瑞典UMEA大学分子生物学博士。

研究方向：林木比较功能基因组学；林木蛋白质结构与功能；林木适应性进化的分子机制。

doi: https://doi.org/10.1111/nph.15430

Journal: New Phytologist

First Published: 11 September, 2018

（P.S. 原文下载：链接:https://pan.baidu.com/s/1qFiSsqwlF_7JjmGMbedfhQ  密码:dmu6）