CLONING, SEQUENCING AND FUNCTIONAL ASSIGNMENT OF THE CHLOROPHYLL BIOSYNTHESIS GENE, CHLP, OF SYNECHOCYSTIS SP PCC-6803

A gene from the cyanobacterium Synechocystis sp, PCC 6803 has been clo ned and sequenced, and subsequently used to partially complement a bch P mutant of the purple photosynthetic bacterium Rhodobacter sphaeroide s. This mutant is blocked in the terminal hydrogenation steps of bchIa biosynthesis and possesses only bchI esterified with geranylgeraniol. It also has a reduced cellular level of the light-harvesting LH2 comp lex, and the 850 nm absorbance maximum of LH2 is red-shifted by approx imately 6 nm. Upon heterologous expression of the Synechocystis bchP h omologue, not only are hydrogenated forms of bchIaGG detectable, but t he level of LH2 is increased and the red-shift reversed by several nm, We conclude that this gene, which rye term chlP, encodes the enzyme c atalysing the stepwise hydrogenation of geranylgeraniol to phytol duri ng chla biosynthesis.