Characterization and functional analyses of the chitinase-encoding genes in the nematode-trapping fungus Arthrobotrys oligospora

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, 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.

Chitinase from Thermomyces lanuginosus SSBP and its biotechnological applications

“…grisea., N. crassa, A. niger, A. nidulans, Mycosphaerella fijiensis, Myc. graminicola and Coccidoides immitis) and basidiomycetes (Postia placenta, Phanerochaete chrysosporium, Laccaria bicolor) are characterized by the presence of only 2-3 ORFs encoding subgroup B chitinases (Seidl et al 2005;Yang et al 2013). …”

CAZyme content of Pochonia chlamydosporia reflects that chitin and chitosan modification are involved in nematode parasitism

“…() suggested that chitinases from P. chlamydosporia could also be involved in insect cuticle damage. Other nematophagous fungi, such as A. oligospora , use extracellular enzymes to degrade nematode cuticles (Tunlid and Jansson, ; Yang et al ., ) as well as nematotoxins (Olthof and Estey, ) involved in its trapping nematophagous lifestyle (Nordbring‐Hertz, ). The CAZymes encoded in A. oligospora genome reveal that this fungus not only has kept a complete PCW degradation machinery, but also has a chitinolytic degradation arsenal, though less numerous than the P. chlamydosporia chitin modifying enzymes.…”

Random mutagenesis analysis and identification of a novel C2H2-type transcription factor from the nematode-trapping fungus Arthrobotrys oligospora

“…Total RNA was extracted with Trizol Reagent (Invitrogen, Carlsbad, California), purified with a RNeasy Mini Kit (Qiagen, Valencia, Califonia), and then reverse transcribed with PrimeScript RT reagent Kit (Takara, Shiga, Japan) by following the manufacturer’s instructions. RT-PCR was conducted according to our recent report 56 . β-tubulin gene (AOL_s00076g640) of A. oligospora was used as the internal control.…”