Characterization of fcp4 and fcp12, two additional genes encoding light harvesting proteins of Cyclotella cryptica (Bacillariophyceae) and phylogenetic analysis of this complex gene family

Two additional cDNA clones containing genes which encode fucoxanthin chlorophyll a/c binding proteins (Fcps) of the centric diatom Cyclotella cryptica have been sequenced. The first cDNA clone containing fcp12 had an insert size of 871 base pairs (bp). The open reading frame (ORF) of 693 bp corresponds to a precursor protein of 231 amino acids with a molecular weight (Mr) of 25 200. For the mature Fcp12, a protein of 196 amino acids with a Mr of 21 700 is proposed. The second cDNA clone contained the fragmentary fcp4 with an insert of 805 bp. The ORF of 492 bp corresponds to a polypeptide of 164 amino acids with a Mr of 18 050. Phylogenetic analyses revealed that the proteins Fcp1, Fcp2, Fcp3 and Fcp5 are closely related to the Fcps of other diatoms, whereas Fcp6, Fcp7 and Fcp12 share the highest homology to the Fcp of the haptophyte Isochrysis galbana and to the light inducible proteins LI818r3 and LI818 of Chlamydomonas reinhardtii and Chlamydomonas eugametos. The subunit Fcp4 revealed some homology with the red algal LH subunits LhcaR1 and LhcaR2 of Porphyridium cruentum.