Human lipoproteins comprise at least 12 different classes that are lognormally distributed.

This study presents the results of HPLC, a gentler and rapid separation method in comparison with the conventional ultracentrifugation, for 55 human serum samples. The elution patterns were analysed parametrically, and the attribute of each class was confirmed biochemically. Human samples contained 12 classes of lipoproteins, each of which may consist primarily of proteins. There are three classes of VLDLs. The level of each class was distributed lognormally, and the standard amount and the 95% range were estimated. Some lipoprotein classes with a narrow range could become ideal indicators of specific diseases. This lognormal character suggests that the levels are controlled by the synergy of multiple factors; multiple undesirable lifestyle habits may drastically increase the levels of specific lipoprotein classes. Lipoproteins in medical samples have been measured by enzymatic methods that coincide with conventional ultracentrifugation; however, the high gravity and time required for ultracentrifugation can cause sample degradation. Actually, the enzymatic methods measured the levels of several mixed classes. The targets of enzymatic methods have to be revised.

Water and CO2 permeability of SsAqpZ, the cyanobacterium Synechococcus sp. PCC7942 aquaporin.

BACKGROUND INFORMATION: Cyanobacteria possess Aquaporin-Z (AqpZ) membrane channels which have been suggested to mediate the water efflux underlying osmostress-inducible gene expression and to be essential for glucose metabolism under photomixotrophic growth. However, preliminary observations suggest that the biophy-sical properties of transport and physiological meaning of AqpZ in such photosynthetic microorganisms are not yet completely assessed. RESULTS: In this study, we used Xenopus laevis oocyte and proteoliposome systems to directly demonstrate the water permeability of the cyanobacterium Synechococcus sp. PCC7942 aquaporin, SsAqpZ. By an in vitro assay of intracellular acidification in yeast cells, SsAqpZ was found to transport also CO2 . Consistent with this result, during the entire exponential phase of growth, Synechococcus SsAqpZ-null-mutant cells grew slower than the corresponding wild-type cells. This phenotype was stronger with higher levels of extracellular CO2 . In line with the conversion of CO2 gas into HCO3(-) ions under alkaline conditions, the impairment in growth of the SsAqpZ-null strain was weaker in more alkaline culture medium. CONCLUSIONS: Cyanobacterial SsAqpZ may exert a pleiotropic function in addition to the already reported roles in macronutrient homeostasis and osmotic-stress response as it appears to constitute an important pathway in CO2 uptake, a fundamental step in photosynthesis.

New Compounds Induce Brassinosteroid Deficient-like Phenotypes in Rice.

Brassinosteroids (BRs) are steroidal plant hormones with potent plant growth promoting activity. Because BR-deficient mutants of rice exhibit altered plant architecture and important agronomic traits, we conducted a systemic search for specific inhibitors of BR biosynthesis to manipulate the BR levels in plant tissues. Although previous studies have been conducted with BR biosynthesis inhibitors in dicots, little is known regarding the effects of BR biosynthesis inhibition in monocot plants. In this work, we used potent inhibitors of BR biosynthesis in Arabidopsis, and we performed a hydroponic culture of rice seedlings to evaluate the effects of BR biosynthesis inhibition. Among the test compounds, we found that 1-[[2-(4-Chlorophenyl)-4-(phenoxymethyl)-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole (1) is a potent inhibitor that could induce phenotypes in rice seedlings that were similar to those observed in brassinosteroid deficient plants. The IC50 value for the retardation of plant growth in rice seedlings was approximately 1.27 ± 0.43 µM. The IC50 value for reducing the bending angle of the lamina joint was approximately 0.55 ± 0.15 µM.

Aquaporin OsPIP1;1 promotes rice salt resistance and seed germination.

OsPIP1;1 is one of the most abundant aquaporins in rice leaves and roots and is highly responsible to environmental stresses. However, its biochemical and physiological functions are still largely unknown. The oocyte assay data showed OsPIP1;1 had lower water channel activity in contrast to OsPIP2;1. EGFP and immunoelectron microscopy studies revealed OsPIP1;1 was predominantly localized in not only plasma membrane but also in some ER-like intracellular compartments in the cells. OsPIP1;1 exhibited low water channel activity in Xenopus oocytes but coexpression of OsPIP2;1 significantly enhanced its water permeability. Stop-flow assay indicated that 10His-OsPIP1;1-reconstituted proteoliposomes had significantly higher water permeability than the control liposomes. Overexpression of OsPIP1;1 greatly altered many physiological features of transgenic plants in a dosage-dependent manner. Moderate expression of OsPIP1;1 increased rice seed yield, salt resistance, root hydraulic conductivity, and seed germination rate. This work suggests OsPIP1;1 functions as an active water channel and plays important physiological roles.

Carbohydrate metabolism in mutants of the cyanobacterium Synechococcus elongatus PCC 7942 defective in glycogen synthesis.

ADP-glucose pyrophosphorylase (AGPase) and glycogen synthase (GS) catalyze the first two reactions of glycogen synthesis in cyanobacteria. Mutants defective in each of these enzymes in Synechococcus elongatus PCC 7942 were constructed and characterized. Activities of the corresponding enzymes in the selected mutants were virtually undetectable, and their ability to synthesize glycogen was entirely abolished. The maximal activities of photosynthetic O(2) evolution and the rates of respiration in the dark were significantly decreased in the mutants compared to those in wild-type cells. Addition of 0.2 M NaCl or 3 mM H(2)O(2) to liquid cultures markedly inhibited the growth of the AGPase and GS mutants, while the same treatment had only marginal effects on the wild type. These results suggest a significant role for storage polysaccharides in tolerance to salt or oxidative stress.

Mechanism of strong quenching of photosystem II chlorophyll fluorescence under drought stress in a lichen, Physciella melanchla, studied by subpicosecond fluorescence spectroscopy.

The mechanism of the severe quenching of chlorophyll (Chl) fluorescence under drought stress was studied in a lichen Physciella melanchla, which contains a photobiont green alga, Trebouxia sp., using a streak camera and a reflection-mode fluorescence up-conversion system. We detected a large 0.31 ps rise of fluorescence at 715 and 740 nm in the dry lichen suggesting the rapid energy influx to the 715-740 nm bands from the shorter-wavelength Chls with a small contribution from the internal conversion from Soret bands. The fluorescence, then, decayed with time constants of 23 and 112 ps, suggesting the rapid dissipation into heat through the quencher. The result confirms the accelerated 40 ps decay of fluorescence reported in another lichen (Veerman et al., 2007 [36]) and gives a direct evidence for the rapid energy transfer from bulk Chls to the longer-wavelength quencher. We simulated the entire PS II fluorescence kinetics by a global analysis and estimated the 20.2 ns(-1) or 55.0 ns(-1) energy transfer rate to the quencher that is connected either to the LHC II or to the PS II core antenna. The strong quenching with the 3-12 times higher rate compared to the reported NPQ rate, suggests the operation of a new type of quenching, such as the extreme case of Chl-aggregation in LHCII or a new type of quenching in PS II core antenna in dry lichens.

Role of the aquaporin PIP1 subfamily in the chilling tolerance of rice.

Although an association between chilling tolerance and aquaporins has been reported, the exact mechanisms involved in this relationship remain unclear. We compared the expression profiles of aquaporin genes between a chilling-tolerant and a low temperature-sensitive rice variety using real-time PCR and identified seven genes that closely correlated with chilling tolerance. Chemical treatment experiments, by which rice plants were induced to lose their chilling tolerance, implicated the PIP1 (plasma membrane intrinsic protein 1) subfamily member genes in chilling tolerance. Of these members, changes in expression of the OsPIP1;3 gene suggested this to be the most closely related to chilling tolerance. Although OsPIP1;3 showed a much lower water permeability than members of the OsPIP2 family, OsPIP1;3 enhanced the water permeability of OsPIP2;2 and OsPIP2;4 when co-expressed with either of these proteins in oocytes. Transgenic rice plants (OE1) overexpressing OsPIP1;3 showed an enhanced level of chilling tolerance and the ability to maintain high OsPIP1;3 expression levels under low temperature treatment, similar to that of chilling-tolerant rice plants. We assume that OsPIP1;3, constitutively overexpressed in the leaf and root of transgenic OE1 plants, interacts with members of the OsPIP2 subfamily, thereby improving the plants' water balance under low temperatures and resulting in the observed chilling tolerance of the plants.

Functional expression and characterization of an archaeal aquaporin. AqpM from methanothermobacter marburgensis.

Researchers have described aquaporin water channels from diverse eubacterial and eukaryotic species but not from the third division of life, Archaea. Methanothermobacter marburgensis is a methanogenic archaeon that thrives under anaerobic conditions at 65 degrees C. After transfer to hypertonic media, M. marburgensis sustained cytoplasmic shrinkage that could be prevented with HgCl(2). We amplified aqpM by PCR from M. marburgensis DNA. Like known aquaporins, the open reading frame of aqpM encodes two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Unlike other known homologs, the putative Hg(2+)-sensitive cysteine was found proximal to the first NPA motif in AqpM, rather than the second. Moreover, amino acids distinguishing water-selective homologs from glycerol-transporting homologs were not conserved in AqpM. A fusion protein, 10-His-AqpM, was expressed and purified from Escherichia coli. AqpM reconstituted into proteoliposomes was shown by stopped-flow light scattering assays to have elevated osmotic water permeability (P(f) = 57 microm x s(-1) versus 12 microm x s(-1) of control liposomes) that was reversibly inhibited with HgCl(2). Transient, initial glycerol permeability was also detected. AqpM remained functional after incubations at temperatures above 80 degrees C and formed SDS-stable tetramers. Our studies of archaeal AqpM demonstrate the ubiquity of aquaporins in nature and provide new insight into protein structure and transport selectivity.

Historical perspective on microalgal and cyanobacterial acclimation to low- and extremely high-CO(2) conditions.

Reports in the 1970s from several laboratories revealed that the affinity of photosynthetic machinery for dissolved inorganic carbon (DIC) was greatly increased when unicellular green microalgae were transferred from high to low-CO(2) conditions. This increase was due to the induction of carbonic anhydrase (CA) and the active transport of CO(2) and/or HCO(3) (-) which increased the internal DIC concentration. The feature is referred to as the 'CO(2)-concentrating mechanism (CCM)'. It was revealed that CA facilitates the supply of DIC from outside to inside the algal cells. It was also found that the active species of DIC absorbed by the algal cells and chloroplasts were CO(2) and/or HCO(3) (-), depending on the species. In the 1990s, gene technology started to throw light on the molecular aspects of CCM and identified the genes involved. The identification of the active HCO(3) (-) transporter, of the molecules functioning for the energization of cyanobacteria and of CAs with different cellular localizations in eukaryotes are examples of such successes. The first X-ray structural analysis of CA in a photosynthetic organism was carried out with a red alga. The results showed that the red alga possessed a homodimeric beta-type of CA composed of two internally repeating structures. An increase in the CO(2) concentration to several percent results in the loss of CCM and any further increase is often disadvantageous to cellular growth. It has recently been found that some microalgae and cyanobacteria can grow rapidly even under CO(2) concentrations higher than 40%. Studies on the mechanism underlying the resistance to extremely high CO(2) concentrations have indicated that only algae that can adopt the state transition in favor of PS I could adapt to and survive under such conditions. It was concluded that extra ATP produced by enhanced PS I cyclic electron flow is used as an energy source of H(+)-transport in extremely high-CO(2) conditions. This same state transition has also been observed when high-CO(2) cells were transferred to low CO(2) conditions, indicating that ATP produced by cyclic electron transfer was necessary to accumulate DIC in low-CO(2) conditions.