Selection of Reference Genes for qRT-PCR in Bletilla striata under Heat Stress

Abstract

Bletilla striata (Thunb.) Reihb.f., a traditional Chinese herbal medicine, has attracted increasing attention because of its wide range of applicability to the medical field and chemical industry. B. striata has been identified to be particularly sensitive to high temperatures. Thus, the study of temperature stress on gene transcription is of interest in the field. Use of reliable reference genes is essential for qRT-PCR analysis of genes. However, little information regarding suitable reference genes for the genus Bletilla has been published. In this study, the sequences of seven potential reference genes in B. striata were obtained via a homology cloning strategy. These genes were as follows: glyceraldehydes-3-phosphate dehydrogenase (GAPDH), 18S ribosomal RNA (18S), elongation factor 1 alpha (EF1α), α-tubulin (TUA), β-tubulin (TUB), ubiquitin (UBI), and NAC domain protein (NAC). We then evaluated the stability levels of these transcripts in different tissues (root, tuber, and leaf) exposed to high temperature using three conventional software and comprehensive RefFinder algorithms. The results indicated that 18S and TUB were the best internal control genes among different periods of heat treatment and that a combination of 18S and UBI was the best in different tissues. Altogether, 18S and UBI were identified to be the best reference genes for all the samples, while NAC and TUA were the least stable reference genes. The results will be useful for studies on target gene expression in plants of the Bletilla genus.