Figure 3

Chloroplast Retargeting of Ferredoxin. The T. oceanica nuclear ferredoxin protein sequence is aligned to its chloroplast counterparts from T. pseudonana and P. tricornutum. The PETF gene is composed of two exons, the second of which encodes the complete conserved part of the protein and is clearly of chloroplast origin, while the first exon contributes the chloroplast retargeting part and is of nuclear origin. Such a modular gene structure is not uncommon in genes encoding chloroplast targeted products as can be seen at the T. oceanica LI818 gene belonging to the large group of nuclear FCP genes. The LI818 gene encodes a cp transit peptide in a structurally separated exon and is presented as a potential donor gene candidate to provide the freshly transferred PETF DNA segment with the required targeting module.