| Summary: | <i>Pratylenchus loosi</i> is an important root-lesion nematode that causes damage to tea plantations in Iran and all over the world. The present study reports on the characterization and evolution of three ß-1,4-endoglucanase genes: <i>Pl-eng</i>-2, <i>Pl-eng</i>-3 and <i>Pl-eng</i>-4. The gene structure of <i>Pl-eng</i>-2 was fully determined with the predicted signal peptide and devoid of the linker domain and carbohydrate-binding domain, while <i>Pl-eng</i>-3 and <i>Pl-eng</i>-4 were only partially sequenced. The transcription of <i>Pl-eng</i>-2 was localized in the secretory esophageal glands of all life stages, but it was upregulated in male and female stages. The exon/intron structures of <i>Pl-eng</i>-2, <i>Pl-eng</i>-3 and <i>Pl-eng</i>-4 confirmed that they resulted from gene duplication followed by sequence and gene structure diversification with loss of the linker domain and carbohydrate-binding domain during evolution. A phylogenetic analysis further confirmed that nematode endoglucanases resulted from the horizontal gene transfer of a bacterial gene, as <i>Pl-eng</i>-3 showed sister relationships with the <i>Cel</i>B cellulase of <i>Bacillus subtilis</i>. Silencing <i>Pl-eng</i>-2 by in vitro RNA interference produced a 60% decrease of the transcript level. The reproductive ability of silenced <i>P. loosi</i> showed a 35% reduction of eggs and larval stages compared to untreated nematodes, suggesting that this gene is involved in the early steps of invasion.
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