Abstract
Pratylenchus loosi 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: Pl-eng-2, Pl-eng-3 and Pl-eng-4. The gene structure of Pl-eng-2 was fully determined with the predicted signal peptide and devoid of the linker domain and carbohydrate-binding domain, while Pl-eng-3 and Pl-eng-4 were only partially sequenced. The transcription of Pl-eng-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 Pl-eng-2, Pl-eng-3 and Pl-eng-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 Pl-eng-3 showed sister relationships with the CelB cellulase of Bacillus subtilis. Silencing Pl-eng-2 by in vitro RNA interference produced a 60% decrease of the transcript level. The reproductive ability of silenced P. loosi 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.
Highlights
Root-lesion nematodes (RLN) belonging to the genus Pratylenchus Filipjev 1936 [1] consist of about 100 species identified so far and are considered as one of the most devastating migratory nematodes, along with root-knot and cyst nematodes [2,3,4]
All life stages can penetrate the root, freely move inside the root, feed and destroy tissues through the combination of mechanical action and secretion of cell wall-modifying enzymes (CWMPs). These nematode secreted proteins are present in plant parasitic nematodes and play an important role in plant-nematode interactions, allowing the penetration, migration and evasion of host defenses [6,7,8,9,10,11,12,13]. These enzymes have been acquired by horizontal gene transfer (HGT) from bacteria or fungi [14,15]
PCR amplification performed on the genomic DNA of P. loosi using ENG1 and ENG2degenerated primers [5] generated a product of about 460 bp
Summary
Root-lesion nematodes (RLN) belonging to the genus Pratylenchus Filipjev 1936 [1] consist of about 100 species identified so far and are considered as one of the most devastating migratory nematodes, along with root-knot and cyst nematodes [2,3,4]. All life stages can penetrate the root, freely move inside the root, feed and destroy tissues through the combination of mechanical action and secretion of cell wall-modifying enzymes (CWMPs). These nematode secreted proteins are present in plant parasitic nematodes and play an important role in plant-nematode interactions, allowing the penetration, migration and evasion of host defenses [6,7,8,9,10,11,12,13]. No information on the cell wall-modifying enzymes in the tea nematode Pratylenchus loosi Loof 1960 [18] is reported in the literature. Pratylenchus loosi is considered a serious nematode pest causing yield losses in tea plantations in Iran and all over the world [19]
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