Molecular characterization of cDNA encoding oxygen evolving enhancer protein 1 increased by salt treatment in the mangrove Bruguiera gymnorrhiza

Young plants of the common Okinawa mangrove species Bruguiera gymnorrhiza w ere transferred from freshwater to a medium with seawater salt level (500 m M NaCl), Two-dimensional gel electrophoresis revealed in the leaf extract o f the plant a 33 kDa protein with pi 5.2, whose quantity increased as a res ult of NaCI treatment, The N-terminal amino acids sequence of this protein had a significant homology with mature region of oxygen evolving enhancer p rotein 1 (OEE1) precursor. The cloning of OEE1 precursor cDNA fragment was carried out by means of reverse transcription-PCR (RT-PCR) using degenerate d primers, Both 3'- and 5'-regions were isolated by rapid amplification of cDNA ends (RACE) method. The deduced amino acid sequence consisted of 322 a mino acids and was 87% identical to that of Nictiana tabacum. In B.gymnorrh iza, the predicted amino acid sequence of the mature protein starts at the residue number 85 of the open reading frame. The first 84-amino acid residu es correspond to a typical transit sequence for the signal directing OEE1 t o its appropriate compartment of chloroplast. The expression of OEE1,was an alyzed together with other OEE subunits and DI protein of photosystem II. T he transcript levels of all the three OEEs were enhanced by NaCI treatment, but the significant increase of D1 protein was not observed.