Sequence Analysis and Gene Expression of Potential Components of Copper Transport and Homeostasis in Thalassiosira pseudonana

Genes involved with many Fe functions and some Cu functions are annotated in the Thalassiosira pseudonana Hasle et Heimdal genome. Using bioinformatics, we performed a systematic Blastp search to obtain all relevant sequences and to select the most complete gene models for putative components of Cu acquisition and distribution. We identified homologs of high-affinity Cu transporters (CTR), Cu transporting P1B-type ATPases, Cu chaperones and ZIP transporters. The putative CTRs in T. pseudonana have the conserved CTR Cu-binding motifs and transmembrane domains, and their gene expression was down-regulated by a Cu addition to low Cu acclimated cultures. The sequences of some putative TpZIPs were similar to those of well-known Zn and Fe transporters. Cu addition affected the expression of some TpZIP genes, suggesting an interaction between Cu metabolism and that of Zn and/or Fe. For intracellular Cu distribution, we identified putative Cu transporting P1B-type ATPases, proposed to deliver Cu to the trans-Golgi or the secretory compartment, as well as putative Cu chaperones, proposed to deliver Cu to the mitochondrion. Their gene expression was down-regulated by a Cu addition, indicating that these putative intracellular Cu transporters and chaperones might redistribute Cu, allowing T. pseudonana to meet key metabolic needs under Cu deficiency.