Identification and Validation of Reference Genes for the Normalization of Gene Expression Data in qRT-PCR Analysis in Aphis gossypii (Hemiptera: Aphididae)

To obtain accurate and reliable results from quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis, it is necessary to select suitable reference genes as standards for normalizing target gene expression data. QRT-PCR is a popular analytical methodology for studying gene expression and it has been used widely in studies of Aphis gossypii Glover in recent years. However, there is absence of study on the stability of the expression of reference genes in A. gossypii. In this study, eight commonly used candidate reference genes, including 18S, 28S, beta-ACT, GAPDH, EF1 alpha, RPL7, alpha-TUB, and TBP, were evaluated under various experimental conditions to assess their suitability for use in the normalization of qRT-PCR data. The optimal number of reference genes was determined using the geNorm program, and the suitability of particular reference genes was empirically validated by performing normalizations of expression data for the HSP70 gene. The results showed the most suitable combinations of reference genes for the different experimental conditions. For experiments based on divergent developmental stages, EF1 alpha, beta-ACT, and RPL7 are the optimal reference gene combination, both EF1 alpha and beta-ACT are the optimal combination used in the experiments of different geographical populations, whereas for experiments of the temperature changes, the combination of GAPDH and RPL7 is optimal, both 18S and beta-ACT are an optimal combination for feeding assay experiments. These research results should be useful for the selection of the suitable reference genes to obtain reliable qRT-PCR data in the gene expression study of A. gossypii.