Abstract

Background Polygonum cuspidatum of the Polygonaceae family is a traditional medicinal plant with many bioactive compounds that play important roles in human health and stress responses. Research has attempted to identify biosynthesis genes and metabolic pathways in this species, and quantitative real-time PCR (RT-qPCR) has commonly been used to detect gene expression because of its speed, sensitivity, and specificity. However, no P. cuspidatum reference genes have been identified, which hinders gene expression studies. Here, we aimed to identify suitable reference genes for accurate and reliable normalization of P. cuspidatum RT-qPCR data. Results Twelve candidate reference genes, including nine common ( ACT , TUA , TUB , GAPDH , EF-1γ , UBQ , UBC , 60SrRNA , and eIF6A ) and three novel ( SKD1 , YLS8 , and NDUFA13 ), were analyzed in different tissues (root, stem, and leaf) without treatment and in leaves under abiotic stresses (salt, ultraviolet [UV], cold, heat, and drought) and hormone stimuli (abscisic acid [ABA], ethylene [ETH], gibberellin [GA 3 ], methyl jasmonate [MeJA], and salicylic acid [SA]). Expression stability in 65 samples was calculated using the △CT method, geNorm, NormFinder, BestKeeper, and RefFinder. Two reference genes ( NDUFA13 and EF-1γ ) were sufficient to normalize gene expression across all sample sets. They were also the two most stable genes for abiotic stresses and different tissues, whereas NDUFA13 and SKD1 were the top two choices for hormone stimuli. Considering individual experimental sets, GAPDH was the top-ranked gene under ABA, ETH, and GA 3 treatments, while 60SrRNA showed good stability under MeJA and cold treatments. ACT , UBC , and TUB were suitable genes for drought, UV, and ABA treatments, respectively. TUA was not suitable because of its considerable variation in expression under different con