Honoring Bacon Ke at 100: a legend among the many luminaries and a highly collaborative scientist in photosynthesis research.

Bacon Ke, who did pioneering research on the primary photochemistry of photosynthesis, was born in China on July 26, 1920, and currently, he is living in a senior home in San Francisco, California, and is a centenarian. To us, this is a very happy and unique occasion to honor him. After providing a brief account of his life, and a glimpse of his research in photosynthesis, we present here "messages" for Bacon Ke@ 100 from: Robert Alfano (USA), Charles Arntzen (USA), Sandor Demeter (Hungary), Richard A. Dilley (USA), John Golbeck (USA), Isamu Ikegami (Japan), Ting-Yun Kuang (China), Richard Malkin (USA), Hualing Mi (China), Teruo Ogawa (Japan), Yasusi Yamamoto (Japan), and Xin-Guang Zhu (China).

Influence of state-2 transition on the proton motive force across the thylakoid membrane in spinach chloroplasts.

The proton motive force (pmf) across the thylakoid membrane is composed of the proton gradient and the membrane potential, which promotes millisecond-delayed light emission (ms-DLE). In this study, the time courses of LHC II phosphorylation and ms-DLE were investigated in spinach chloroplast during State-2 transition. Red light illumination resulted in an exponential rise in LHC II phosphorylation and a biphasic time course of ms-DLE. The phospho-LHC II appeared upon approximately 1 min illumination. The phosphorylation level increased exponentially when illumination was elongated to 20 min. The t((1/2) )of saturated LHC II phosphorylation was estimated 4-5 min under present illumination. During this process, the amplitudes of ms-DLE increased transiently to a maximal amplitude within 0.5 min illumination, and the reached maximum of the fast phase of ms-DLE was approximately 140% of the dark control. Then, ms-DLE decreased from the maximum. After > or =3 min illumination, ms-DLE decreased to a lower level than the dark control. In the presence of uncouplers and inhibitors, the transient increase in the biphasic time course of ms-DLE was removed by nigericin and DCMU, and the sequential decrease was delayed by DCCD. The time course was not affected significantly by valinomycin and DBMIB. Moreover, the level of LHC II phosphorylation was enhanced by nigericin, valinomycin and DCCD, and was inhibited completely by DCMU and partially by DBMIB. Taken together, we proposed that the PS II photochemical activity remained unaffected even with a higher level of LHC II phosphorylation, which was reflected by the effect of DCCD on the time course of ms-DLE. Probably, the evidence of LHC II phosphorylation is the rearrangement of LHC II-PS II complex and the thylakoid, a feedback to light-exposure, rather than the redistribution of excitation energy from PS II to PS I.

Photosynthesis research in the People's Republic of China.

The first research paper on photosynthesis in China was published by T.T. Li(2) in 1929. Two photosynthesis laboratories were established in Shanghai and Beijing in the 1950s and the 1960s, respectively. A photophosphorylation 'intermediate' was discovered after the energy conversion process was separated into light and dark phases in the 1960s. Since the 1980s, research has accelerated at several different levels through efforts of a large number of scientists in China.

Low concentrations of NaHSO(3) increase cyclic photophosphorylation and photosynthesis in cyanobacterium Synechocystis PCC6803.

Application of NaHSO(3) solution at low concentrations (20-200 muM) to the culture medium enhanced photosynthetic oxygen evolution in cyanobacterium Synechocystis PCC6803 by more than 10%. The slow phase of ms-DLE was strengthened, showing that the transmembrane proton motive force related to photophosphorylation was enhanced. It was also observed that dry weight as well as ATP content under illuminated conditions were both increased after the treatment, indicating that low concentrations of NaHSO(3) could enhance the supply of ATP and thus increase biomass accumulation. In accord with the promotion in the photosynthetic oxygen evolution and ATP content, the transient increase in chlorophyll fluorescence after the termination of actinic light was increased; and meanwhile, the half-time of re-reduction of P700(+) in the presence of DCMU after a pulse light under background far-red light was shortened by approximately 30%, indicating that cyclic electron flow around PS I was accelerated by the treatment. Based on these results it is suggested that the increase in photosynthesis in Synechocystis PCC6803 caused by low concentrations of NaHSO(3) solution might be due to the stimulation of the cyclic electron flow around PS I and thus the increase in photophosphorylation.

Site-directed Mutagenesis of epsilon Subunit of ATP Synthase of Maize Chloroplast.

The effects of some residues in maize chloroplast epsilon subunit on its activity have been studied by site-directed mutagenesis. After replacing Thr-42 of epsilon subunit with Cys, Arg, Ile or Pro, and forming the mutant epsilonT42C, mutant epsilonT42R, mutant epsilonT42I and mutant epsilonT42P respectively, it was found that the mutant epsilonT42P protein could no longer be expressed, but expression of other epsilon subunit mutants was similar to that of wild type. Comparing the inhibitory potency of different mutants of epsilon subunit with that of the wild type, it was found that the inhibitory effects of epsilon subunit mutants epsilonT42C and epsilonT42R on ATPase activity were slightly higher than that of wild type, but the epsilonT42I protein strongly inhibited the Ca(2+)-ATPase activity.