Gene expression assays for actin, ubiquitin, and three microsatellite-encoding genes in Helianthus annuus (Asteraceae).

PREMISE OF THE STUDY

The "tuning knob" model of King et al. (Endeavor 21: 36-40, 1997) postulates that microsatellite mutations can alter phenotypes in a stepwise fashion. Some proposed mechanisms involve regulation of gene expression. To study the effect of microsatellites harbored in untranslated regions on gene expression in Helianthus annuus, we have developed TaqMan assays for three microsatellite-encoding genes, and two constitutively expressed genes, actin and ubiquitin, to serve as standards.

METHODS AND RESULTS

All five TaqMan assays yielded strong log-linear relationships between cycle threshold (C(T)) values and cDNA concentrations (R(2) = 0.98-0.99). Standard curves were based on five concentrations for each of five individuals. Efficiencies ranged from 0.83 to 1.03.

CONCLUSIONS

The developed tools will allow for relative quantification of gene expression across individuals. Genotyping these loci will allow for testing the "tuning knob" hypothesis. Further, the actin and ubiquitin assays should be generally applicable to gene expression studies in H. annuus.