Reference gene selection for qRT-PCR analysis of flower development in Lagerstroemia indica and L. speciosa

Quantitative real-time polymerase chain reaction (qRT-PCR) is a prevalent method for gene expression analysis, depending on the stability of the reference genes for data normalization. Lagerstroemia indica and L. speciosa are popular ornamental plants which are famous for the long flowering period. However, no systematic studies on reference genes in Lagerstroemia have yet been conducted. In the present study, we selected nine candidate reference genes (GAPDH, TUA, TUB, 18S, RPII, EF-1α, ATC, EIF5A and CYP) and evaluated their expression stability in different tissues during floral development of L. indica and L. speciosa using four algorithms (geNorm, NormFinder, BestKeeper and, RefFinder). Results showed that RPII and EF-1α were the most stably expressed and suitable reference genes for both of Lagerstroemia species. Moreover, ACT exhibited high expression stability in L. indica and GAPDH was a suitable reference gene for L. speciosa in different flower development stages. TUB was an unsuitable reference gene for gene expression normalization due to significant variations in expression across all samples. Finally, we verified the reliability of the selected candidate reference genes by amplifying an AGAMOUS homolog (LsAG1) of Arabidopsis thaliana. This study provides a list of suitable reference genes, thereby broadening the genetic basis of the gene expression patterns in Lagerstroemia species.