| Summary: | The glycoside hydrolase family 16 (GH16) is widely found in prokaryotes and eukaryotes, and hydrolyzes the β-1,3(4)-linkages in polysaccharides. Notably, the rice white tip nematode <i>Aphelenchoides besseyi</i> harbors a higher number of GH16s compared with other plant-parasitic nematodes. In this work, two GH16 genes, namely AbGH16-1 and AbGH16-2, were isolated and characterized from <i>A. besseyi</i>. The deduced amino acid sequences of AbGH16-1 and AbGH16-2 contained an N-terminal signal peptide and a fungal Lam16A glucanase domain. Phylogenetic analysis revealed that AbGH16-1 and AbGH16-2 clustered with ascomycete GH16s, suggesting AbGH16-1 and AbGH16-2 were acquired by horizontal gene transfer from fungi. In situ hybridization showed that both AbGH16-1 and AbGH16-2 were specifically expressed in the nematode gonads, correlating with qPCR analysis that showed the high transcript levels of the two genes in the female nematodes. AbGH16-1 and AbGH16-2 were also significantly induced in nematodes feeding on <i>Botrytis cinerea</i>. Characterization of the recombinant protein showed AbGH16-1 and AbGH16-2 displayed pronounced inhibition of both conidial germination and germ tube elongation of <i>B. cinerea</i>. In addition, silencing of AbGH16-1 and AbGH16-2 by RNA interference significantly decreased the reproduction ability of <i>A. besseyi</i> and had a profound impact on the development process of offspring in this nematode. These findings have firstly proved that GH16s may play important roles in <i>A.besseyi</i> feeding and reproduction on fungi, which thus provides novel insights into the function of GH16s in plant-parasitic nematodes.
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