Chitinases are involved in multiple aspects of fungal life cycle, such as cell wall remodelling, chitin degradation and mycoparasitism lifestyle. To improve our knowledge of the chitinase molecular evolution of Ascomycota, the gene family of 72 representatives of this phylum was identified and subjected to phylogenetic, evolution trajectory and selective pressure analyses. Phylogenetic analysis showed that the chitinase gene family size and enzyme types varied significantly, along with species evolution, especially for groups B and C. In addition, two new subgroups, C3 and C4, are recognized in group C chitinases. Random birth and death testing indicated that gene expansion and contraction occurred in most of the taxa, particularly for species in the order Hypocreales (class Sordariomycetes). From an enzyme function point of view, we speculate that group A chitinases are mainly involved in species growth and development, while the expansion of genes in group B chitinases is related to fungal mycoparasitic and entomopathogenic abilities, and, to a certain extent, the expansion of genes in group C chitinases seems to be correlated with the host range broadening of some plant-pathogenic fungi in Sordariomycetes. Further selection pressure testing revealed that chitinases and the related amino acid sites were under positive selection in the evolutionary history, especially at the nodes sharing common ancestors and the terminal branches of Hypocreales. These results give a reasonable explanation for the size and function differences of chitinase genes among ascomycetes, and provide a scientific basis for understanding the evolutionary trajectories of chitinases, particularly that towards a mycoparasitic lifestyle.

中文翻译：

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子囊菌中几丁质酶的比较分子进化，重点是寄生生活方式

几丁质酶参与真菌生命周期的多个方面，如细胞壁重塑、几丁质降解和真菌寄生生活方式。为了提高我们对子囊菌几丁质酶分子进化的认识，鉴定了该门的 72 个代表的基因家族，并对其进行了系统发育、进化轨迹和选择压力分析。系统发育分析表明，随着物种进化，几丁质酶基因家族的大小和酶类型发生了显着变化，特别是对于 B 组和 C 组。此外，在 C 组几丁质酶中发现了两个新的亚组 C3 和 C4。随机出生和死亡测试表明，大多数分类群都发生了基因扩张和收缩，特别是对于 Hypocreales （Sordariomycetes 类）中的物种。从酶功能的角度来看，我们推测A组几丁质酶主要参与物种的生长发育，而B组几丁质酶的基因扩增与真菌寄生和昆虫致病能力有关，在一定程度上C组几丁质酶的基因扩增似乎与与Sordariomycetes中某些植物病原真菌的宿主范围扩大有关。进一步的选择压力测试表明，几丁质酶及其相关氨基酸位点在进化历史上处于正选择状态，特别是在共享共同祖先的节点和Hypocreales的末端分支处。这些结果合理解释了子囊菌中几丁质酶基因的大小和功能差异，为了解几丁质酶的进化轨迹提供了科学依据，