The light-independent biogenesis of photosystem in dark-grown lotus （Nelumbo nucifera Gaertn.）seedling,The light-independent biogenesis of photosystem in dark-grown lotus （Nelumbo nucifera Gaertn.）seedling

Abstract

It is well known that angiosperms need light to form chlorophyll. Photosystem biogenesis is not found in dark-grown angiosperm seedlings. Nelumbo nucifera, which has a unique position in the phylogeny of the angiosperm, is special in that its seeds contain chlorophyll and LHCII. In this report, it is showed that both PSII and PSI could be formed in lotus seedling during ten-day germination in dark. This can be proved by the following three evidences. First, with in situ fluorescence detection at 77K, lotus embryo had only single fluorescence emission peak at 678 nm before germination while this peak red shifted to 682 nm during the dark-grown process. At the same time, the peak at 691 nm belonging to PSII and the peak at 725nm emitted from PSI begin to appeared and increased gradually with prolong of the germination time. Second, with SDS-PAGE, PSI chlorophyll-protein complexes band could be showed clearly in lotus seedling grown in the dark for 10 days. Western Blots also demonstrated the existence of Lhca1 protein, which is part of the source of PSI fluorescence emission at 725nm; Third, measurement of electron transport activities showed that chloroplast isolated from dark-grown lotus seedling had PSI reduce activity, but no PSII oxygen evolving activity. After addition of electron donor DPC, the light-driven DCIP reduce activity could be detected. These results showed that even though the PSII and PSI formed in the dark-grown lotus seedling, the water-splitting system of PSII is underdeveloped.