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This study aimed to develop an effective method for the expression and purification of the Dermatophagoides farinae serpin protein and to establish an experimental foundation for elucidating its role in the temperature stress response. The total RNA of D. farinae was extracted, and specific primers were designed for serpin amplification. Serpin was joined with pET32a vector and transformed into BL21 (DE3) cells. Expression of recombinant proteins was induced. Proteins were extracted by enzymatic lysis or enzymatic lysis combined with ultrasonication. Recombinant proteins were purified by Ni-NTA method. SDS-PAGE was conducted to evaluate protein expression, extraction, and purification efficiency. Agarose gel electrophoresis and sequencing analysis showed that the amplified serpin open reading frame was 1284 bp, encoding a hydrophilic and stable protein with a relative molecular weight of 48.30 kD. SDS-PAGE demonstrated that there was a specific band at 55-70 kD, which was consistent with the predicted size of the recombinant pET32a-Serpin protein. Enzymatic lysis combined with 30% ultrasonic power promoted the release of soluble protein more effectively than enzymatic lysis alone. 16 °C for 4 h was optimal for inducing expression. The optimal imidazole concentrations for washing non-His-tagged protein and eluting His-tagged protein were determined to be 20 mM and 200 mM, respectively. In this study, A prokaryotic expression and purification system for the D. farinae serpin protein was successfully established, providing a technical reference for functional gene research in mites at the protein level., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Dermatophagoides farinae, an important pathogen, has multiple allergens. However, their expression under physiological conditions are not understood. Our previous RNA-seq showed that allergens of D. farinae were up-regulated under temperature stress, implying that they may be involved in stress response. Here, we performed a comprehensive study. qRT-PCR detection indicated that 26 of the 34 allergens showed differential expression. Der f1 had the most abundant basic expression quantity. Der f 28.0201 (HSP70) and Der f3 had the same regulation pattern in 9 highly expressed transcripts, which only up-regulated at 41 °C and 43 °C, but Der f 28.0201 showed stronger regulation than Der f 3 (19.88-fold vs 6.02-fold). Whereas Der f 1, 2, 7, 21, 22, 27, and 30 were up-regulated under both heat and cold stress, and Der f 27 showed the strongest regulation ability among them. Der f 27 showed more significant up-regulation than Der f 28.0201 under heat stress (23.59-fold vs 19.88-fold), and Der f27 had more obvious up-regulation under cold than heat stress (30.70-fold vs 23.59-fold). The expression of Der f 27, 28.0201 and 1, and D. farinae survival rates significantly decreased following RNAi, indicating the upregulation of these allergens under temperature stress conferred thermo-tolerance or cold-tolerance to D. farinae. In this study, we described for the first time that these allergens have temperature-stress response functions. This new scientific discovery has important clinical value for revealing the more frequent and serious allergic diseases caused by D. farinae during the change of seasons., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Dermatophagoides farinae is an important source of indoor allergens that shows strong tolerance to external temperatures. However, the regularity and mechanism of tolerance are still unclear. Based on our previous RNA-seq and annotation of D. farinae under temperature stress, it is planned to identify differentially expressed genes (DEGs) involved in the temperature stress response by quantitative real-time PCR (qRT-PCR). However, the lack of reference genes directly limited the detection and confirmation of DEGs. Accordingly, in this study, we have selected six candidates as reference genes in D. farinae: 60S RP L11, 60S RP L21, α tubulin, GAPDH, Der f Mal f 6, and calreticulin, and evaluated their expression stabilities as affected by heat and cold stresses, using geNorm, NormFinder, BestKeeper, comparative ΔCt and RefFinder methods. Then the expression level of 15 DEGs were detected and verified. geNorm analysis showed that α tubulin and calreticulin were the most stable reference genes under heat stress and cold stress of D. farinae. Similar evaluation results were obtained by NormFinder and BestKeeper, in which 60S RP L21 and α tubulin were the most stable reference genes. By comparative ΔCt method and a comprehensive evaluation of RefFinder, α tubulin was identified as the most ideal reference gene of D. farinae under heat and cold stresses. Furthermore, qRT-PCR detection results of 15 DEGs were almost identical to the RNA-seq results, indicating that α tubulin is stable as a reference gene. This study provided technical support for DEGs expression studies in D. farinae using qRT-PCR., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Demodex is a type of parasitic mite which could cause serious dermatoses in 11 orders of mammals. However, due to the tiny body with thick chitin hard to be ruptured as well as the difficulty in obtaining a large number of mites, the quantity and quality of extracted RNA could hardly satisfied for transcriptome sequencing. This has hampered the research on functional genes and molecular pathogenesis of Demodex for a long time. To solve the problems above, the present study established a new RNA extraction method in combination Azanno method with liquid nitrogen grinding using 16 human and canine Demodex mite samples. The RNA quality detection results of Agilent 2100 Bioanalyzer showed that 8 of 16 RNA samples met the requirements for trace RNA-Seq, with RIN of 5.0-6.5 and RNA quantity of 1.1-16.0 ng. RNA quality was affected by grinding process and parasitic position of Demodex. Enough grinding number (≥2000) in moderate time (≤20 min) was significant for mites' complete rupture and RNA degradation prevention. D. brevis (100%, 3/3) parasitizing in human sebaceous glands had significantly higher RNA qualification rate than D. folliculorum (57.14%, 4/7) parasitizing in human hair follicles. Yet D. canis parasitizing in dog had lower RNA qualification rate (16.67%, 1/6) as mites were embedded in skin tissues and blood clots. It should be pointed out that microplate reader had defects with a lower RNA qualification rate of 6.25% (1/16) unmatched with 2100 Bioanalyzer, reminding that it could be only used as reference in RNA quality evaluation., (Copyright © 2019 Elsevier Inc. All rights reserved.)