Experimental analysis of origin and phylogeny of chloroplasts in algae

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On the origin of chloroplasts, there are two alternative hypotheses ; that is monophyletic and multiphyletic.Based on the gene sequence in chloroplasts, monophyletic hypothesis is rather favorable, however this should be confirmed by other methods.Thus, we investigated the phylogeny of two kinds of polypeptides which are functioning in chloroplasts, (1) antenna pigment-protein complexes and (2) electron transport components.1.Mimuro and Gantt isolated a light harvesting complex I (LHC I) from the red alga Porphyridium cruentum, and characterized the specttoscopic properties.The energy transfer from carotenoid (beta-carotene or zeaxanthin) to chlorophyll alpha was clearly shown for the first time by the low temperature spectra.2.Ikeuchi and Plumley isolated a highly purified photosystem I complex from a diatom Cylindrotheca sp.for the first time and determined the N-terminal sequence of several polypeptides.Among them, they identified psaD and also obtained several new components.3.Presence of cytochrome c55 was investigated in several algal species.This component is known to be present in cyanobacteria and function as a water oxidizing component.Since heme is not necessary for that function, its real function has been controversial.Mimuro and Gantt tried to identify cyt c550 in P.cruentum, however they failed to do in USA.Thus, they again tried in Japan using a highly sensitive photometer, and finally identified cyt c550 together with the other cytochromes (cyt b6, cyt559 and cyt c553).Mimuro and Gantt agreed to analyze the stoichiometry between cyt c550 and photosystem II reaction center near in future.4.Ikeuchi and Plumley started to grow Heterosigma sp, Raphidophyceae, to analyze the diversity of components in photosynthesis.5.We four agreed to continue the research for the next few years by applying again to this program.