Quantification of diatom gene expression in the sea by selecting uniformly transcribed mRNA as the basis for normalization.

To quantify gene expressions by quantitative reverse transcription-PCR (Q-RT-PCR) in natural diatom assemblages, it is necessary to seek a biomass reference specific to the target species. Two housekeeping genes, TBP (encoding the TATA box-binding protein) and EFL (encoding the translation elongation factor-like protein), were evaluated as candidates for reference genes in Q-RT-PCR assays. Transcript levels of TBP and EFL were relatively stable under various test conditions including growth stages, light-dark cycle phases, and nutrient stresses in Skeletonema costatum and Chaetoceros affinis, and TBP expression was more stable than that of EFL.