Molecular Characterization of Chitin Synthase Gene of Demodex canis from Mizoram, India.

AIMS: Canine demodicosis is a parasitic condition affecting the skin of dogs. The present study was designed to characterize chitin synthase gene of Demodex canis. The molecular technique was used for better understanding of this gene. METHODS: A total of 75 dogs which are reared as pets with or without showing any skin lesions were examined during the study period. Skin scrapings were examined by indirect method using 10% potassium hydroxide solution under 10 × microscope. DNA samples were extracted from positive skin samples and were subjected to PCR for molecular identification. RESULTS: A total of 25 dogs irrespective of age, sex, breed or coat showed positive result for D. canis. The PCR revealed a single amplified product of 339 bp length which exactly matched with D. canis. The chitin synthase gene was amplified by PCR, subsequently cloned, sequenced, and compared with available data in GenBank for the particular gene of D. canis. Only one single nucleotide polymorphism (SNP) was noticed at 231 position of the chitin synthase gene sequence when compared to other isolates. CONCLUSION: The molecular technique confirms with the morphological identity of D. canis. This report signifies the value of peculiar tool to identify 'follicular mite' even from apparently healthy skin.

Silencing NADPH-cytochrome P450 reductase results in reduced acaricide resistance in Tetranychus cinnabarinus (Boisduval).

Cytochrome P450 monooxygenases (P450s) are involved in metabolic resistance to insecticides and require NADPH cytochrome P450 reductase (CPR) to transfer electrons when they catalyze oxidation reactions. The carmine spider mite, Tetranychus cinnabarinus is an important pest mite of crop and vegetable plants worldwide, and its resistance to acaricides has quickly developed. However, the role of CPR on the formation of acaricide-resistance in T. cinnabarinus is still unclear. In this study, a full-length cDNA encoding CPR was cloned and characterized from T. cinnabarinus (designated TcCPR). TcCPR expression was detectable in all developmental stages of T. cinnabarinus, but it's much lower in eggs. TcCPR was up-regulated and more inducible with fenpropathrin treatment in the fenpropathrin-resistant (FeR) strain compared with the susceptible SS strain. Feeding of double-strand RNA was effective in silencing the transcription of TcCPR in T. cinnabarinus, which resulted in decreasing the activity of P450s and increasing the susceptibility to fenpropathrin in the FeR strain but not in the susceptible strain. The current results provide first evidence that the down-regulation of TcCPR contributed to an increase of the susceptibility to fenpropathrin in resistant mites. TcCPR could be considered as a novel target for the development of new pesticides.

[Why are some allergens enzymes?]. / Pourquoi certains allergènes sont-ils des enzymes?

In the last ten years, progress in the field of allergy research has led to the purification of some of the major allergens and to a better knowledge of their physico-chemical properties. A number of studies have shown that some allergens have enzymatic activities. Molecular biology has provided the means to clone and sequence genes encoding these allergens and to produce recombinant allergens in yeast and bacteria. Epitope mapping of natural and synthetic allergens, using polyclonal or monoclonal antibodies and cell-stimulation tests, has also contributed greatly to the understanding of their immunogenicity and allergenicity. Analysis of these new data allow us to explain why some allergens are enzymes.