Characterization and functional analyses of the chitinase-encoding genes in the nematode-trapping fungus Arthrobotrys ol
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Original Paper
Characterization and functional analyses of the chitinase‑encoding genes in the nematode‑trapping fungus Arthrobotrys oligospora Jinkui Yang · Yan Yu · Juan Li · Wei Zhu · Zongyi Geng · Dewei Jiang · Yunchuan Wang · Ke‑Qin Zhang
Received: 25 February 2013 / Revised: 8 April 2013 / Accepted: 11 April 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract Nematode-trapping fungi can secrete many extracellular hydrolytic enzymes such as serine proteases and chitinases to digest and penetrate nematode/egg-cuticles. However, little is known about the structure and function of chitinases in these fungi. In this study, 16 ORFs encoding putative chitinases, which all belong to glycoside hydrolase (GH) family 18, were identified from the Arthrobotrys oligospora genome. Bioinformatics analyses showed that these 16 putative chitinases differ in their functional domains, molecular weights and pI. Phylogenetic analysis grouped these A. oligospora chitinases into four clades: clades I, II, III and IV, respectively, including an A. oligospora-specific subclade (Clade IV-B) that contained high-molecular weight chitinases (≥100 kDa). Transcriptional analysis of A. oligospora chitinases suggested that the expression of most chitinases was repressed by carbon starvation, and all chitinases were up-regulated under nitrogen starvation. However, chitinase AO-190 was up-regulated under carbon and/or nitrogen starvation. Moreover, Communicated by Erko Stackebrandt. Jinkui Yang and Yan Yu contributed equally to this work. Electronic supplementary material The online version of this article (doi:10.1007/s00203-013-0894-6) contains supplementary material, which is available to authorized users. J. Yang · Y. Yu · J. Li · W. Zhu · Z. Geng · D. Jiang · Y. Wang · K.-Q. Zhang (*) Laboratory for Conservation and Utilization of Bio‑Resources, and Key Laboratory of Microbial Diversity in Southwest China, Ministry of Education, Yunnan University, Kunming 650091, People’s Republic of China e-mail: [email protected] J. Yang e-mail: [email protected]
several chitinases (such as AO-59, AO-190 and AO-801) were up-regulated in the presence of chitinous substrates or a plant pathogenic fungus, indicating that they could play a role in biocontrol applications of A. oligospora. Our results provided a basis for further understanding the functions, diversities and evolutionary relationships between chitinase genes in nematode-trapping fungi. Keywords Arthrobotrys oligospora · Chitinase · Domain structure · Phylogenetic analysis · Real-time PCR · Transcriptional analysis
Introduction Chitin, a polymer of β-(1,4)-linked N-acetylglucosamine, is an essential structural component of fungal cell walls, shells of nematode eggs and exoskeletons of arthropods. Family 18 chitinases, which degrade this polymer, play key roles in the life cycles of pathogenic fungi (Lorito et al. 1996). Fungi can produce chitinases throughout their growth cycle, and these enzymes are believed to contribute to morphogenetic and pathogenic processes, includ
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