Reference Gene Selection in the Desert Plant Eremosparton songoricum

The drought-tolerant plant Eremosparton songoricum (Litv.) Vass. is a leafless perennial clone-forming semi-shrub. It is a rare endemic plant of central Asia and is the only species of the genus in China, where it is found only in the Gurbantunggut desert. As a rare and extremely drought-tolerant Leguminosae shrub, E. songoricum is being developed as a model organism for investigating the morphological, biochemical, physiological and molecular adaptations and responses to water deficit. The ability to identify and compare the expression profiles of key genes involved in these mechanisms would provide a powerful tool for evaluating the molecular changes in plants adapted to the desert environment.

Quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) technology has been widely used in gene expression analysis. Many qRT-PCR expression studies have focused on humans and other animal model organisms. In plants, stable reference genes have been identified for grasses, fruits, vegetables and commercial agricultural crops. However, few studies have been conducted using legumes, and almost all of the reports published have utilized herbaceous plants and have not included E. songoricum.

In order to clone and evaluate candidate reference genes for expression studies in the Leguminosae shrubby plant E. songoricum, samples were collected from different E. songoricum tissues at different developmental stages and exposed to different stress treatments. Researchers conducted detailed expression analysis of the transcription factor EsDREB2 in E. songoricum to illustrate the utility of the characterized reference genes.

GeNorm analysis indicated that expression stability varied between the reference genes in the different experimental conditions, but the two most stable reference genes were sufficient for normalization in most conditions. EsEF and Esα-TUB were sufficient for various stress conditions, EsEF and EsACT were suitable for samples of differing germination stages, and EsGAPDH and EsUBQ were most stable across multiple adult tissue samples. The Es18S gene was unsuitable as a reference gene in the analysis. In addition, the expression level of the drought-stress related transcription factor EsDREB2 verified the utility of E. songoricum reference genes and indicated that no single gene was adequate for normalization on its own. This is the first systematic report on the selection of reference genes in E. songoricum, and these data will facilitate future work on gene expression in this species.

The result has been published on International Journal of Molecular Sciences, 2012, 13: 6944-6963. The paper can be downloaded from http://www.mdpi.com/1422-0067/13/6/6944/htm.