Abstract
In High-Nutrient, Low-Chlorophyll area in the oceans, it has been strongly suggested that the growth and photosynthesis of phytoplankton are limited by iron starvations. However, molecular mechanisms to respond to iron starvation are not known in diatoms. In this study, we investigated iron-responsive promoters in 2 marine diatoms, Thalassiosira pseudonana and Phaeodactylum tricornutum. In our preliminary study, it was demonstrated that diatoms cells alter their photosynthetic affinity to dissolved-inorganic carbon upon iron limitations. Semi-quantitative RT-PCR analysis revealed that mRNA accumulations of 2 genes in T. pseudonana and 11 genes in P. tricornutum increased upon iron starvations. DNA sequences upstream the regions of iron permease1 (FTR1) in T. pseudonana, ferrichrome binding protein1 (FBP1), flavodoxin (Fld) and iron starvation induced protein1 (Isi1) in P. tricornutum were isolated and characterized by GFP or GUS reporter assays. As a result, all putative promoters were upregulated upon iron starvation, indicated that they include iron-responsive elements.
