Selection of reference genes for gene expression normalization in Pyropia yezoensis using quantitative real-time PCR

Quantitative real-time PCR (qRT-PCR) is frequently used for gene expression analysis. The selection of reference genes is required for normalization of the variation to avoid misinterpretation of experimental results and erroneous analyses. Pyropia yezoensis, growing in the intertidal zone, is an economically important seaweed. Although this intertidal seaweed has been an experimental system for understanding stress tolerance and developmental mechanisms, reference genes suitable for the normalization of qRT-PCR data have not previously been identified. In this study, expression stability of six candidate reference genes, including ACT, eIF4A, EF1 alpha, GAPDH, TUA, and UBQ (traditional housekeeping genes), has been validated in a diverse set of samples representing different developmental stages and stress conditions of P. yezoensis. Three qRT-PCR analysis methods, geNorm, NormFinder, and BestKeeper, were evaluated systematically. The results indicated that ACT3, eIF4A, and EF1 alpha were the optimal reference genes for P. yezoensis under stress conditions; UBQ, EF1 alpha, and eIF4A were suitable for studying the expression of genes related to P. yezoensis development. TUA showed the lowest expression stability both under stress conditions and over developmental stages. Our results have provided a reference gene application guideline for P. yezoensis gene expression characterization using the qRT-PCR system.