Evaluation of expression stability of reference genes ovEF1alpha and 18S rRNA under GA3 treatments and temperature and light stresses in Thyme genus

Real-time PCR technique is available for determining changes of gene expression. However, normalizing gene expression data and obtaining reliable results depends on the selection of appropriate reference genes which are stably expressed under different experimental conditions. In this study, we investigated suitability of two commonly used reference genes [elongation factor 1 alpha (OvEF1alpha) and 18S ribosomal RNA (18S rRNA)] in seven Thyme populations and under exogenously applied gibberellic acid (GA3) hormone (control, 30, 60 and 90ppm), plant age (young plants and middle-aged plants and temperature/light stress. Results showed that expression levels of both genes in all populations were affected significantly. Plant age did not significantly effect on expression of the two genes. Also, ovEF1alpha unaffected by exogenously applied GA3. Under temperature/light stress, expression of OvEF1alpha increased in Babgorgy population but in Babzangy decreased. In contrast, expression of 18S rRNA in Babgorgy was significantly decreased but has stable expression in Thyme and Babzangy. Thus, these results showed that ovEF1alpha for comparison of gene expression between Thyme, Hanza, Sirch and Zarand and 18S rRNA for Babzangy, Sirch and Hanza or Zarand and Thyme populations are suitable as internal control gene. Also, for temperature/light stress both genes are suitable in Thymus vulgaris L. but only 18SrRNA is suitable in Thymus caramanicus Jalas.