Unique chlorophylls in picoplankton Prochlorococcus sp. "Physicochemical properties of divinyl chlorophylls, and the discovery of monovinyl chlorophyll b as well as divinyl chlorophyll b in the species Prochlorococcus NIES-2086".

In this review, we introduce our recent studies on divinyl chlorophylls functioning in unique marine picoplankton Prochlorococcus sp. (1) Essential physicochemical properties of divinyl chlorophylls are compared with those of monovinyl chlorophylls; separation by normal-phase and reversed-phase high-performance liquid chromatography with isocratic eluent mode, absorption spectra in four organic solvents, fluorescence information (emission spectra, quantum yields, and life time), circular dichroism spectra, mass spectra, nuclear magnetic resonance spectra, and redox potentials. The presence of a mass difference of 278 in the mass spectra between [M+H]+ and the ions indicates the presence of a phytyl tail in all the chlorophylls. (2) Precise high-performance liquid chromatography analyses show divinyl chlorophyll a' and divinyl pheophytin a as the minor key components in four kinds of Prochlorococcus sp.; neither monovinyl chlorophyll a' nor monovinyl pheophytin a is detected, suggesting that the special pair in photosystem I and the primary electron acceptor in photosystem II are not monovinyl but divinyl-type chlorophylls. (3) Only Prochlorococcus sp. NIES-2086 possesses both monovinyl chlorophyll b and divinyl chlorophyll b, while any other monovinyl-type chlorophylls are absent in this strain. Monovinyl chlorophyll b is not detected at all in the other three strains. Prochlorococcus sp. NIES-2086 is the first example that has both monovinyl chlorophyll b as well as divinyl chlorophylls a/b as major chlorophylls.

Randomized study of lafutidine vs lansoprazole in patients with mild gastroesophageal reflux disease.

AIM: To compare the clinical efficacy of the second-generation H2RA lafutidine with that of lansoprazole in Japanese patients with mild gastroesophageal reflux disease (GERD). METHODS: Patients with symptoms of GERD and a diagnosis of grade A reflux esophagitis (according to the Los Angeles classification) were randomized to receive lafutidine (10 mg, twice daily) or lansoprazole (30 mg, once daily) for an initial 8 wk, followed by maintenance treatment comprising half-doses of the assigned drug for 24 wk. The primary endpoint was the frequency and severity of heartburn during initial and maintenance treatment. The secondary endpoints were the sum score of questions 2 and 3 in the Gastrointestinal Symptom Rating Scale (GSRS), and the satisfaction score. RESULTS: Between April 2012 and March 2013, a total of 53 patients were enrolled, of whom 24 and 29 received lafutidine and lansoprazole, respectively. After 8 wk, the frequency and severity of heartburn was significantly reduced in both groups. However, lafutidine was significantly inferior to lansoprazole with regard to the severity of heartburn during initial and maintenance treatment (P = 0.016). The sum score of questions 2 and 3 in the GSRS, and satisfaction scores were also significantly worse in the lafutidine group than the lansoprazole group (P = 0.0068 and P = 0.0048, respectively). CONCLUSION: The clinical efficacy of lafutidine was inferior to that of lansoprazole, even in Japanese patients with mild GERD.

Harvesting Far-Red Light by Chlorophyll f in Photosystems I and II of Unicellular Cyanobacterium strain KC1.

Cells of a unicellular cyanobacterium strain KC1, which were collected from Japanese fresh water Lake Biwa, formed chlorophyll (Chl) f at 6.7%, Chl a' at 2.0% and pheophytin a at 0.96% with respect to Chl a after growth under 740 nm light. The far-red-acclimated cells (Fr cells) formed extra absorption bands of Chl f at 715 nm in addition to the major Chl a band. Fluorescence lifetimes were measured. The 405-nm laser flash, which excites mainly Chl a in photosystem I (PSI), induced a fast energy transfer to multiple fluorescence bands at 720-760 and 805 nm of Chl f at 77 K in Fr cells with almost no PSI-red-Chl a band. The 630-nm laser flash, which mainly excited photosystem II (PSII) through phycocyanin, revealed fast energy transfer to another set of Chl f bands at 720-770 and 810 nm as well as to the 694-nm Chl a fluorescence band. The 694-nm band did not transfer excitation energy to Chl f. Therefore, Chl a in PSI, and phycocyanin in PSII of Fr cells transferred excitation energy to different sets of Chl f molecules. Multiple Chl f forms, thus, seem to work as the far-red antenna both in PSI and PSII. A variety of cyanobacterial species, phylogenically distant from each other, seems to use a Chl f antenna in far-red environments, such as under dense biomats, in colonies, or under far-red LED light.

Site-directed mutagenesis of amino acid residues of D1 protein interacting with phosphatidylglycerol affects the function of plastoquinone QB in photosystem II.

Recent X-ray crystallographic analysis of photosystem (PS) II at 1.9-Å resolution identified 20 lipid molecules in the complex, five of which are phosphatidylglycerol (PG). In this study, we mutagenized amino acid residues S232 and N234 of D1, which interact with two of the PG molecules (PG664 and PG694), by site-directed mutagenesis in Synechocystis sp. PCC 6803 to investigate the role of the interaction in PSII. The serine and asparagine residues at positions 232 and 234 from the N-terminus were mutagenized to alanine and aspartic acid, respectively, and a mutant carrying both amino acid substitutions was also produced. Although the obtained mutants, S232A, N234D, and S232AN234D, exhibited normal growth, they showed decreased photosynthetic activities and slower electron transport from QA to QB than the control strain. Thermoluminescence analysis suggested that this slower electron transfer in the mutants was caused by more negative redox potential of QB, but not in those of QA and S2. In addition, the levels of extrinsic proteins, PsbV and PsbU, were decreased in PSII monomer purified from the S232AN234D mutant, while that of Psb28 was increased. In the S232AN234D mutant, the content of PG in PSII was slightly decreased, whereas that of monogalactosyldiacylglycerol was increased compared with the control strain. These results suggest that the interactions of S232 and N234 with PG664 and PG694 are important to maintain the function of QB and to stabilize the binding of extrinsic proteins to PSII.

Photosynthesis of root chloroplasts developed in Arabidopsis lines overexpressing GOLDEN2-LIKE transcription factors.

In plants, genes involved in photosynthesis are encoded separately in nuclei and plastids, and tight cooperation between these two genomes is therefore required for the development of functional chloroplasts. Golden2-like (GLK) transcription factors are involved in chloroplast development, directly targeting photosynthesis-associated nuclear genes for up-regulation. Although overexpression of GLKs leads to chloroplast development in non-photosynthetic organs, the mechanisms of coordination between the nuclear gene expression influenced by GLKs and the photosynthetic processes inside chloroplasts are largely unknown. To elucidate the impact of GLK-induced expression of photosynthesis-associated nuclear genes on the construction of photosynthetic systems, chloroplast morphology and photosynthetic characteristics in greenish roots of Arabidopsis thaliana lines overexpressing GLKs were compared with those in wild-type roots and leaves. Overexpression of GLKs caused up-regulation of not only their direct targets but also non-target nuclear and plastid genes, leading to global induction of chloroplast biogenesis in the root. Large antennae relative to reaction centers were observed in wild-type roots and were further enhanced by GLK overexpression due to the increased expression of target genes associated with peripheral light-harvesting antennae. Photochemical efficiency was lower in the root chloroplasts than in leaf chloroplasts, suggesting that the imbalance in the photosynthetic machinery decreases the efficiency of light utilization in root chloroplasts. Despite the low photochemical efficiency, root photosynthesis contributed to carbon assimilation in Arabidopsis. Moreover, GLK overexpression increased CO2 fixation and promoted phototrophic performance of the root, showing the potential of root photosynthesis to improve effective carbon utilization in plants.