LSU rDNA D5 region: the DNA barcode for molecular classification and identification of Demodex

Whether ribosomal genes can be used as DNA barcodes for molecular identification of Demodex (Acariformes: Demodicidae) is unclear. To examine this, Demodex folliculorum, D. brevis, D. canis, and D. caprae were collected for DNA extraction, rDNA fragments amplification, sequencing, and analysis. The V2 and V4 regions of SSU rDNA; D5, D6, and D8 regions of LSU rDNA; and ITS region were obtained from the four morphospecies. BLAST analysis showed that the obtained sequences matched those of Demodex or Aplonobia (Acariformes: Tetranychidae) in Raphignathae. Phylogenetic trees derived from V2, V4, D5, D6, and D8 regions, but not from ITS region, showed that the four species of Demodex clustered independently. Sequence divergence analysis further demonstrated that D5, D6, and D8 regions had obvious barcoding gap between intraspecific and interspecific divergences, with the gap of D5 (16.91%) larger than that of D6 (11.82%) and D8 (4.66%). The V2 and V4 regions did not have a barcoding gap, as the intraspecific and interspecific divergences partially overlapped. For the ITS region, intraspecific and interspecific divergences completely overlapped. These results suggest that the D5, D6, and D8 regions of LSU rDNA, especially D5, are suitable DNA barcodes for Demodex. Key words: Demodex, rDNA fragments, sequence analysis, DNA barcode. Il demeure incertain si les genes ribosomiques peuvent servir de codes a barres de l'ADN pour l'identification moleculaire chez le genre Demodex (Acariformes : Demodicidae). A cette fin, des echantillons de Demodex folliculorum, D. brevis, D. canis et D. caprae ont ete collectes en vue de l'extraction d'ADN, d'amplification de fragments de l'ADNr, de sequencage et d'analyse. Les regions V2 et V4 de l'ADNr de la petite sous-unite, les regions D5, D6 et D8 de l'ADNr de la grande sous-unite, ainsi que l'ITS ont ete obtenues pour les quatre morpho-especes. Des analyses BLAST ont revele que les sequences obtenues correspondaient a celles des genres Demodex ou Aplonobia (Acariformes : Tetranychidae) au sein des Raphignathae. Les arbres phylogenetiques derives des regions V2, V4, D5, D6 et D8, mais non ITS, ont montre que les quatre especes de Demodex formaient des groupes distincts. Une analyse de la divergence des sequences a montre que les regions D5, D6 et D8 presentaient un fosse clair entre les degres de divergence rencontres aux niveaux intra- et interspecifiques, cet ecart etant plus grand chez D5 (a 16,91 %) que chez D6 (11,82 %) et D8 (4,66 %). Les regions V2 et V4 n'ont pas produit de tel fosse du fait que les divergences intra- et interspecifiques se chevauchaient completement. Ces resultats suggerent que les regions D5, D6 et D8 de l'ADNr de la grande sous-unite, particulierement D5, sont aptes a servir de codes a barres chez le genre Demodex. [Traduit par la Redaction] Mots-cles : Demodex, fragments d'ADNr, analyse de sequences, code a barres de l'ADN.
Introduction Mites of the genus Demodex are important pathogens that cause demodicidosis, such as rosacea, blepharitis, and acne in humans, laipi disease in dogs, and skin nodules in goats (Hsu [...]