THE GENE FAMILY ENCODING THE FUCOXANTHIN CHLOROPHYLL PROTEINS FROM THE BROWN ALGA MACROCYSTIS-PYRIFERA

Six members of a multigene family encoding polypeptide constituents of the fucoxanthin, chlorophyll a/c protein complex from female gametoph ytes of the brown alga Macrocystis pyrifera have been cloned and chara cterized. The deduced amino acid sequences are very similar to those o f fucoxanthin chlorophyll binding proteins (Fcp) from the diatom Phaeo dactylum tricornutum and exhibit limited homology to chlorophyll a/b b inding (Cab) polypeptides from higher plants. The primary translation products from the M. pyrifera fcp genes are synthesized as higher mole cular weight precursors that are processed prior to their assembly int o the Fcp complex. The presumed N-terminal 40-amino acid presequence o f the Fcp precursor polypeptide has features resembling that of a sign al sequence. This presequence may be required for the protein to trans verse the endoplasmic reticulum that surrounds the plastid in brown al gae. A subsequent targeting step would be required for the protein to cross the double membrane of the plastid envelope. M. pyrifera fcp tra nscripts are of two sizes, 1.2 and 1.6 kb. The size difference is acco unted for by the length of the 3' untranslated region, which can be up to 1000 bases. Transcript abundance's of members of the fcp gene fami ly are dependent on light quantity, light quality, or both. Transcript levels of one gene increased approximately five- to tenfold in thalli grown in low intensity relative to high intensity white or blue light . Transcripts from this gene also significantly increase in red light relative to blue light at equivalent light intensities.