Selection of Stable Reference Genes for Quantitative Real-Time PCR on Herbaceous Peony (Paeonia lactiflora Pall.) in Response to Drought Stress

Herbaceous peony (Paeonia lactiflora Pall.), as a high-end cut flower in the international market, has high orna-mental and medicinal values. But in Northern China, drought is a major environmental factor influencing the growth and development of P. lactiflora. Quantitative real-time polymerase chain reaction (qRT-PCR) can eval-uate gene expression levels under different stress conditions, and stable internal reference is the key for qRT-PCR. At present, there is no systematic screening of internal reference for correcting gene expressions of P. lactiflora in response to drought stress. In this study, 10 candidate genes [ubiquitin (UBQ2), UBQ1, elongation factor 1-alpha (EF-1 alpha), Histidine (His), eukaryotic initiation factor (eIF), tubulin (TUB), actin (ACT), UBQ3, ACT2, RNA poly-merase II (RNA Pol II)] were chosen, and 4 analysis methods were used to compare the stabilities for these 10 genes coping with drought stress. Due to the difference of operation methods, the results of different analysis were distinct, and the final comprehensive analysis indicated that EF-1 alpha was a relatively stable internal reference gene for P. lactiflora under drought stress. Also, UBQ1 and UBQ2 were the best reference gene combination according to GeNorm analysis. This study will lay a foundation for screening the key genes of P. lactiflora in response to drought stress.