Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.
Fungal Genet Biol. 2012 Sep;49(9):717-30. doi: 10.1016/j.fgb.2012.06.013. Epub 2012 Jul 13.
Glycoside hydrolase family 18 contains hydrolytic enzymes with chitinase or endo-N-acetyl-β-D-glucosaminidase (ENGase) activity, while glycoside hydrolase family 20 contains enzymes with β-N-acetylhexosaminidase (NAGase) activity. Chitinases and NAGases are involved in chitin degradation. Chitinases are phylogenetically divided into three main groups (A, B and C), each further divided into subgroups. In this study, we investigated the functional role of 10 Neurospora crassa genes that encode chitinases, 2 genes that encode ENGases and 1 gene that encode a NAGase, using gene deletion and gene expression techniques. No phenotypic effects were detected for any of the studied group A chitinase gene deletions. Deletion of the B group member chit-1 resulted in reduced growth rate compared with the wild type (WT) strain. In combination with the presence of a predicted glycosylphosphatidylinositol anchor motif in the C-terminal of chit-1, indicating cell wall localization, these data suggest a role in cell wall remodeling during hyphal growth for chit-1. Deletion of the ENGase gene gh18-10 resulted in reduced growth rate compared with WT, increased conidiation, and increased abiotic stress tolerance. In addition, Δgh18-10 strains displayed lower secretion of extracellular proteins compared to WT and reduced levels of extracellular protease activity. The connection between gh18-10 ENGase activity and the endoplasmic reticulum associated protein degradation process, a stringent quality control of glycoprotein maturation, is discussed. N. crassa group C chitinase genes gh18-6 and gh18-8 were both induced during fungal-fungal interactions. However, gh18-6 was only induced during interspecific interactions, while gh18-8 displayed the highest induction levels during self-self interactions. These results provide new information on functional differentiation of fungal chitinases.
糖苷水解酶家族 18 包含具有几丁质酶或内切-N-乙酰-β-D-葡糖胺酶 (ENGase) 活性的水解酶，而糖苷水解酶家族 20 包含具有β-N-乙酰己糖胺酶 (NAGase) 活性的酶。几丁质酶和 NAGase 参与几丁质降解。几丁质酶在系统发育上分为三个主要组（A、B 和 C），每个组进一步分为亚组。在这项研究中，我们使用基因缺失和基因表达技术研究了 10 个编码几丁质酶的粗糙脉孢菌基因、2 个编码 ENGase 的基因和 1 个编码 NAGase 的基因的功能作用。在所研究的 A 组几丁质酶基因缺失中，没有检测到任何表型效应。与野生型（WT）菌株相比，B 组成员 chit-1 的缺失导致生长速度降低。与 chit-1 羧基末端存在预测的糖基磷脂酰肌醇锚定模体结合，表明其在细胞壁中的定位，这些数据表明 chit-1 在菌丝生长过程中在细胞壁重塑中发挥作用。ENGase 基因 gh18-10 的缺失与 WT 相比导致生长速度降低、产孢增加和非生物胁迫耐受性增强。此外，与 WT 相比，Δgh18-10 菌株的细胞外蛋白分泌减少，细胞外蛋白酶活性降低。讨论了 gh18-10 ENGase 活性与内质网相关蛋白降解过程之间的联系，内质网相关蛋白降解过程是糖蛋白成熟的严格质量控制。粗糙脉孢菌 C 组几丁质酶基因 gh18-6 和 gh18-8 在真菌-真菌相互作用中均被诱导。然而，gh18-6 仅在种间相互作用中被诱导，而 gh18-8 在自-自相互作用中显示出最高的诱导水平。这些结果提供了关于真菌几丁质酶功能分化的新信息。
