Chlorophyll Formation in the YG-6 Mutant of Chlorella regularis : Spectral Characterization of Protochlorophyllide Phototransformation

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Dark-grown YG-6 mutant cells of Chlorella regularis accumulate at least two forms of phototransformable protochlorophyllide (Pchlide) with in vivo absorption maxima at 634 nm (Pchlide 634) and 650 nm (Pchlidc 650). Difference spectrophotometric analyses and the action spectra showed that Pchlide 634 is first transformed into the 648 nm form and then phototransformed into chlorophyllide (Chlide) 672 nm. Pchlide 650 is phototransformed into Chlide 685 which then shifts towards short wavelength-forming Chlidc 667 in the subsequent dark stage (Shibata shift). Pchlide 650 is regenerated at the expense of photoinactive Pchlide 632. In washed. cells after the phototransformation, the Shibata shift was accelerated. Freezing/thawing treatment in the dark caused conversion of phototransformable Pchlide 650 into photoinactive Pchlide 633, but phototransformation activity of Pchlide 634 still partly remained. These results suggest that in the final step of light-dependent chlorophyll formation in the YG-6 mutant of C. regularis, two sequentially and functionally separate routes are present: (1) Pchlide 634 → Pchlide 648 → Chlide 672 → Chlorophyll a. (2) Pchlide 650 → Chlide 685 → Chlide 667 → Chlorophyll a.
日本植物生理学会の論文