Chlorophyll a Synthesis in Rhodobacter sphaeroides by Chlorophyll Synthase of Nicotiana tabacum .

The production of phytylated chlorophyll a (Chl a P ) in Rhodobacter sphaeroides , which uses phytylated bacteriochlorophyll a (BChl a P ), is the first step in expanding the light absorption spectra. Unlike the chlorophyll synthase (ChlG) of the Synechocystis sp. PCC6803, ChlGs of angiosperms, including Arabidopsis thaliana , Nicotiana tabacum , Avena sativa , and Oryza sativa , showed bacteriochlorophyll synthase activity and resistance to inhibition by bacteriochlorophyllide a (BChlide a ), geranylgeranylated BChl a (BChl a GG ), and BChl a P , collectively called bacteriochlorins. Among the angiosperm ChlGs, N. tabacum ChlG had the highest bacteriochlorophyll synthase activity and resistance to inhibition by bacteriochlorins. Expression of N. tabacum chlG in R. sphaeroides resulted in the formation of free Chl a P in the presence of BChl a P during photoheterotrophic growth, even though reactive oxygen species were generated.