Molecular evolutionary mechanisms driving functional diversification of α-glucosidase in Lepidoptera.
Molecular evolutionary mechanisms driving functional diversification of α-glucosidase in Lepidoptera.
复制标题
驱动鳞翅目α-葡萄糖苷酶功能多样化的分子进化机制
DOI：
10.1038/srep45787
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发表时间：
2017-04-12
影响因子：
4.6
通讯作者：
Wang H
中科院分区：
文献类型：
--
作者：
Li X;Shi L;Zhou Y;Xie H;Dai X;Li R;Chen Y;Wang H
鳞翅目昆虫的消化道是一个独特的环境，其消化酶的适应性可塑性是鳞翅目昆虫高效吸收营养的关键。然而，很少有人知道消化酶的分子适应这种环境。在此，我们发现鳞翅目α-葡萄糖苷酶，一个关键的消化酶，分化成蔗糖水解酶（SUH）和其他麦芽糖酶亚家族。SUH仅在鳞翅目昆虫中检测到，对蔗糖具有特异性。这表明鳞翅目昆虫已经进化出了增强的水解蔗糖的能力，蔗糖是它们的主要能量来源。基因重复和外显子改组在不同的微共线区域产生多个拷贝的α-葡萄糖苷酶。与麦芽糖酶相比，SUH还表现出明显的功能分化（FD），这与特定谱系和密码子的正选择有关。9个位点，这是参与FD和积极的选择，位于周围的配体结合槽的SUH。这些位点可能是负责配体结合的偏好和水解特异性的SUH蔗糖，并有助于其构象稳定性。总之，我们的研究表明，正选择是α-葡萄糖苷酶适应性多样化的重要进化力量，也是唯一的鳞翅目消化道中膜相关SUH的唯一存在。
The digestive tract of lepidopteran insects is unique given its highly alkaline pH. The adaptive plasticity of digestive enzymes in this environment is crucial to the highly-efficient nutritional absorption in Lepidoptera. However, little is known about the molecular adaptation of digestive enzymes to this environment. Here, we show that lepidopteran α-glucosidase, a pivotal digestive enzyme, diverged into sucrose hydrolase (SUH) and other maltase subfamilies. SUH, which is specific for sucrose, was only detected in Lepidoptera. It suggests that lepidopteran insects have evolved an enhanced ability to hydrolyse sucrose, their major energy source. Gene duplications and exon-shuffling produced multiple copies of α-glucosidase in different microsyntenic regions. Furthermore, SUH showed significant functional divergence (FD) compared with maltase, which was affected by positive selection at specific lineages and codons. Nine sites, which were involved in both FD and positive selection, were located around the ligand-binding groove of SUH. These sites could be responsible for the ligand-binding preference and hydrolytic specificity of SUH for sucrose, and contribute to its conformational stability. Overall, our study demonstrated that positive selection is an important evolutionary force for the adaptive diversification of α-glucosidase, and for the exclusive presence of membrane-associated SUHs in the unique lepidopteran digestive tract.