Ju Yuliang, Wang Xuan, Guan Tinglong, Peng Deliang, Li Hongmei
Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, PR China.
Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, PR China.
Int J Parasitol. 2016 Nov;46(12):819-828. doi: 10.1016/j.ijpara.2016.08.001. Epub 2016 Sep 15.
The glycoside hydrolase family 18 (GH18) of chitinases is a gene family widely expressed in archaes, prokaryotes and eukaryotes, and hydrolyzes the β-1,4-linkages in chitin. The pinewood nematode Bursaphelenchus xylophilus is one of the organisms that produces GH18 chitinases. Notably, B. xylophilus has a higher number of GH18 chitinases compared with the obligate plant-parasitic nematodes Meloidogyne incognita and Meloidogyne hapla. In this study, seven GH18 chitinases were identified and cloned from B. xylophilus based on genomic analyses. The deduced amino acid sequences of all these genes contained an N-terminal signal peptide and a GH18 catalytic domain. Phylogenetic analysis showed that the origin of B. xylophilus GH18 chitinases was independent of those from fungi and bacteria. Real-time quantitative reverse transcription PCR analysis indicated that GH18 chitinase genes had discrete expression patterns, representing almost all the life stages of B. xylophilus. In situ hybridisation showed that the mRNA of GH18 chitinase genes of B. xylophilus were detected mainly in the spermatheca, esophageal gland cells, seminal vesicle and eggs. RNA interference (RNAi) results revealed different roles of GH18 chitinase genes in B. xylophilus. Bx-chi-1, Bx-chi-2 and Bx-chi-7 were associated with reproduction, fungal cell-wall degradation and egg hatching, respectively. Bx-chi-5 and Bx-chi-6 may be involved in sperm metabolism. In conclusion, this study demonstrates that GH18 chitinases have multiple functions in the life cycle of B. xylophilus.
几丁质酶的糖苷水解酶家族18（GH18）是一个在古生菌、原核生物和真核生物中广泛表达的基因家族，可水解几丁质中的β-1,4-连接键。松材线虫是产生GH18几丁质酶的生物之一。值得注意的是，与专性植物寄生线虫南方根结线虫和北方根结线虫相比，松材线虫拥有更多数量的GH18几丁质酶。在本研究中，基于基因组分析从松材线虫中鉴定并克隆出了7种GH18几丁质酶。所有这些基因推导的氨基酸序列均包含一个N端信号肽和一个GH18催化结构域。系统发育分析表明，松材线虫GH18几丁质酶的起源独立于真菌和细菌的GH18几丁质酶。实时定量逆转录PCR分析表明，GH18几丁质酶基因具有不同的表达模式，几乎代表了松材线虫的所有生命阶段。原位杂交显示，松材线虫GH18几丁质酶基因的mRNA主要在受精囊、食管腺细胞、精囊和卵中检测到。RNA干扰（RNAi）结果揭示了GH18几丁质酶基因在松材线虫中的不同作用。Bx-chi-1、Bx-chi-2和Bx-chi-7分别与繁殖、真菌细胞壁降解和卵孵化有关。Bx-chi-5和Bx-chi-6可能参与精子代谢。总之，本研究表明GH18几丁质酶在松材线虫的生命周期中具有多种功能。
