A 3.0 µm Pixels and 1.5 µm Pixels Combined Complementary Metal-Oxide Semiconductor Image Sensor for High Dynamic Range Vision beyond 106 dB.

We propose a new concept image sensor suitable for viewing and sensing applications. This is a report of a CMOS image sensor with a pixel architecture consisting of a 1.5 µm pixel with four-floating-diffusions-shared pixel structures and a 3.0 µm pixel with an in-pixel capacitor. These pixels are four small quadrate pixels and one big square pixel, also called quadrate-square pixels. They are arranged in a staggered pitch array. The 1.5 µm pixel pitch allows for a resolution high enough to recognize distant road signs. The 3 µm pixel with intra-pixel capacitance provides two types of signal outputs: a low-noise signal with high conversion efficiency and a highly saturated signal output, resulting in a high dynamic range (HDR). Two types of signals with long exposure times are read out from the vertical pixel, and four types of signals are read out from the horizontal pixel. In addition, two signals with short exposure times are read out again from the square pixel. A total of eight different signals are read out. This allows two rows to be read out simultaneously while reducing motion blur. This architecture achieves both an HDR of 106 dB and LED flicker mitigation (LFM), as well as being motion-artifact-free and motion-blur-less. As a result, moving subjects can be accurately recognized and detected with good color reproducibility in any lighting environment. This allows a single sensor to deliver the performance required for viewing and sensing applications.

Loss of heterophylly in aquatic plants: not ABA-mediated stress but exogenous ABA treatment induces stomatal leaves in Potamogeton perfoliatus.

Heterophyllous aquatic plants produce aerial (i.e., floating and terrestrial) and submerged leaves-the latter lack stomata-while homophyllous plants contain only submerged leaves, and cannot survive on land. To identify whether differences in morphogenetic potential and/or physiological stress responses are responsible for variation in phenotypic plasticity between two plants types, responses to abscisic acid (ABA) and salinity stress were compared between the closely related, but ecologically diverse pondweeds, Potamogeton wrightii (heterophyllous) and P. perfoliatus (homophyllous). The ABA-treated (1 or 10 µM) P. wrightii plants exhibited heterophylly and produced leaves with stomata. The obligate submerged P. perfoliatus plants were able to produce stomata on their leaves, but there were no changes to leaf shape, and stomatal production occurred only at a high ABA concentration (10 µM). Under salinity stress conditions, only P. wrightii leaves formed stomata. Additionally, the expression of stress-responsive NCED genes, which encode a key enzyme in ABA biosynthesis, was consistently up-regulated in P. wrightii, but only temporarily in P. perfoliatus. The observed species-specific gene expression patterns may be responsible for the induction or suppression of stomatal production during exposure to salinity stress. These results suggest that the two Potamogeton species have an innate morphogenetic ability to form stomata, but the actual production of stomata depends on ABA-mediated stress responses specific to each species and habitat.

Excitation relaxation dynamics and energy transfer in pigment-protein complexes of a dinoflagellate, revealed by ultrafast fluorescence spectroscopy.

Photosynthetic light-harvesting complexes, found in aquatic photosynthetic organisms, contain a variety of carotenoids and chlorophylls. Most of the photosynthetic dinoflagellates possess two types of light-harvesting antenna complexes: peridinin (Peri)-chlorophyll (Chl) a/c-protein, as an intrinsic thylakoid membrane complex protein (iPCP), and water-soluble Peri-Chl a-protein, as an extrinsic membrane protein (sPCP) on the inner surface of the thylakoid. Peri is a unique carotenoid that has eight C=C bonds and one C=O bond, which results in a characteristic absorption band in the green wavelength region. In the present study, excitation relaxation dynamics of Peri in solution and excitation energy transfer processes of sPCP and the thylakoid membranes, prepared from the photosynthetic dinoflagellate, Symbiodinium sp., are investigated by ultrafast time-resolved fluorescence spectroscopy. We found that Peri-to-Chl a energy transfer occurs via the Peri S1 state with a time constant of 1.5 ps or 400 fs in sPCP or iPCP, respectively, and that Chl c-to-Chl a energy transfer occurs in the time regions of 350-400 fs and 1.8-2.6 ps.

Circumnutation on the water surface: female flowers of Vallisneria.

Circumnutation, the helical movement of growing organ tips, is ubiquitous in land plants. The mechanisms underlying circumnutation have been debated since Darwin's time. Experiments in space and mutant analyses have revealed that internal oscillatory (tropism-independent) movement and gravitropic response are involved in circumnutation. Female flower buds of tape grass (Vallisneria asiatica var. biwaensis) circumnutate on the water surface. Our observations and experiments with an artificial model indicated that gravitropism is barely involved in circumnutation. Instead, we show that helical intercalary growth at the base of peduncle plays the primary role in all movements in Vallisneria. This growth pattern produces torsional bud rotation, and gravity and buoyancy forces have a physical effect on the direction of peduncle elongation, resulting in bud circumnutation on the water surface. In contrast to other water-pollinated hydrophilous plants, circumnutation in Vallisneria enables female flowers to actively collect male flowers from a larger surface area of water.

Comparative studies of thermotolerance: different modes of heat acclimation between tolerant and intolerant aquatic plants of the genus Potamogeton.

BACKGROUND AND AIMS: Molecular-based studies of thermotolerance have rarely been performed on wild plants, although this trait is critical for summer survival. Here, we focused on thermotolerance and expression of heat shock transcription factor A2 (HSFA2) and its putative target gene (chloroplast-localized small heat shock protein, CP-sHSP) in two allied aquatic species of the genus Potamogeton (pondweeds) that differ in survival on land. METHODS: The degree of thermotolerance was examined using a chlorophyll bioassay to assess heat injury in plants cultivated under non- and heat-acclimation conditions. Potamogeton HSFA2 and CP-sHSP genes were identified and their heat-induction was quantified by real-time PCR. KEY RESULTS: The inhibition of chlorophyll accumulation after heat stress showed that Potamogeton malaianus had a higher basal thermotolerance and developed acquired thermotolerance, whereas Potamogeton perfoliatus was heat sensitive and unable to acquire thermotolerance. We found two duplicated HSFA2 and CP-sHSP genes in each species. These genes were induced by heat shock in P. malaianus, while one HSFA2a gene was not induced in P. perfoliatus. In non-heat-acclimated plants, transcript levels of HSFA2 and CP-sHSP were transiently elevated after heat shock. In heat-acclimated plants, transcripts were continuously induced during sublethal heat shock in P. malaianus, but not in P. perfoliatus. Instead, the minimum threshold temperature for heat induction of the CP-sHSP genes was elevated in P. perfoliatus. CONCLUSIONS: Our comparative study of thermotolerance showed that heat acclimation leads to species-specific changes in heat response. The development of acquired thermotolerance is beneficial for survival at extreme temperatures. However, the loss of acquired thermotolerance and plasticity in the minimum threshold temperature of heat response may be favourable for plants growing in moderate habitats with limited daily and seasonal temperature fluctuations.

Differential DNA rearrangements of plastid genes, psbA and psbD, in two species of the dinoflagellate Alexandrium.

Plastomes of the peridinin-containing dinoflagellates are composed of a limited number of genes, which are carried individually on small circular molecules, termed 'minicircles'. Although the prevalent plastid chromosome of most algae and plants has only a single copy of each gene, our previous study showed that low copy numbers of multiple variants of the gene psbA co-exist with the 'ordinary' gene encoding the D1 protein in minicircles of Alexandrium tamarense. Although none of the psbA variants encoded the entire protein, they persisted in culture. In this study, we compared the distribution and structure of psbA and psbD variants in two species of Alexandrium to characterize DNA rearrangement within these genes. In addition to four previously reported psbA variants, three psbD variants were found in A. tamarense minicircles. The ordinary psbA and psbD genes also co-existed with variants in another species, A. catenella. The sequences of the ordinary genes were virtually identical in the two species. All the variants comprised insertion or deletion mutations, with no base substitutions being identified. Duplicated parts of the coding sequences were contained in most of the insertions. Short direct repeats (4-14 bp) and/or adenine + thymine-rich motifs were present in all mutation regions, although the position and/or the sequence of each DNA rearrangement was unique to each variant. The results indicated that replication-based repeat-mediated recombination was responsible for generation of the variants.

Identification of transcribed and persistent variants of the psbA gene carried by plastid minicircles in a dinoflagellate.

Plastid genomes of the peridinin-containing dinoflagellates are composed of a limited number of genes that are contained separately on small circular molecules (minicircles). It has been shown that occasionally aberrant minicircles are generated, but they are usually small and contain little coding information. In this study, we discovered multiple variants, a putative "gene family", of the gene psbA in the plastid minicircles of the dinoflagellate Alexandrium tamarense, which have persisted for almost 3 years in culture. Each variant, like the ordinary psbA, existed on distinct minicircles of similar size (5-6 kb). These psbA variants retained all, or almost all, the coding sequence of the ordinary gene, and all four were transcribed and edited after transcription, even though they could not encode the entire protein due to intervening or translocated sequences. Repeat elements were generally found in the relatively large non-coding region of these minicircles. Each psbA variant might have been generated by DNA recombination and/or replication slippage, as for previously reported aberrant minicircles. The fact that these minicircles are transcribed, individually edited and maintained in the genome suggests that they are functionally important, although their precise roles remain unclear.

Molecular adaptation of rbcL in the heterophyllous aquatic plant Potamogeton.

BACKGROUND: Heterophyllous aquatic plants show marked phenotypic plasticity. They adapt to environmental changes by producing different leaf types: submerged, floating and terrestrial leaves. By contrast, homophyllous plants produce only submerged leaves and grow entirely underwater. Heterophylly and submerged homophylly evolved under selective pressure modifying the species-specific optima for photosynthesis, but little is known about the evolutionary outcome of habit. Recent evolutionary analyses suggested that rbcL, a chloroplast gene that encodes a catalytic subunit of RuBisCO, evolves under positive selection in most land plant lineages. To examine the adaptive evolutionary process linked to heterophylly or homophylly, we analyzed positive selection in the rbcL sequences of ecologically diverse aquatic plants, Japanese Potamogeton. PRINCIPAL FINDINGS: Phylogenetic and maximum likelihood analyses of codon substitution models indicated that Potamogeton rbcL has evolved under positive Darwinian selection. The positive selection has operated specifically in heterophyllous lineages but not in homophyllous ones in the branch-site models. This suggests that the selective pressure on this chloroplast gene was higher for heterophyllous lineages than for homophyllous lineages. The replacement of 12 amino acids occurred at structurally important sites in the quaternary structure of RbcL, two of which (residue 225 and 281) were identified as potentially under positive selection. CONCLUSIONS/SIGNIFICANCE: Our analysis did not show an exact relationship between the amino acid replacements and heterophylly or homophylly but revealed that lineage-specific positive selection acted on the Potamogeton rbcL. The contrasting ecological conditions between heterophyllous and homophyllous plants have imposed different selective pressures on the photosynthetic system. The increased amino acid replacement in RbcL may reflect the continuous fine-tuning of RuBisCO under varying ecological conditions.

GENETIC DIVERSITY AND INTROGRESSION IN TWO CULTIVATED SPECIES (PORPHYRA YEZOENSIS AND PORPHYRA TENERA) AND CLOSELY RELATED WILD SPECIES OF PORPHYRA (BANGIALES, RHODOPHYTA)(1).

We investigated the genetic variations of the samples that were tentatively identified as two cultivated Porphyra species (Porphyra yezoensis Ueda and Porphyra tenera Kjellm.) from various natural populations in Japan using molecular analyses of plastid and nuclear DNA. From PCR-RFLP analyses using nuclear internal transcribed spacer (ITS) rDNA and plastid RUBISCO spacer regions and phylogenetic analyses using plastid rbcL and nuclear ITS-1 rDNA sequences, our samples from natural populations of P. yezoensis and P. tenera showed remarkably higher genetic variations than found in strains that are currently used for cultivation. In addition, it is inferred that our samples contain four wild Porphyra species, and that three of the four species, containing Porphyra kinositae, are closely related to cultivated Porphyra species. Furthermore, our PCR-RFLP and molecular phylogenetic analyses using both the nuclear and plastid DNA demonstrated the occurrence of plastid introgression from P. yezoensis to P. tenera and suggested the possibility of plastid introgression from cultivated P. yezoensis to wild P. yezoensis. These results imply the importance of collecting and establishing more strains of cultivated Porphyra species and related wild species from natural populations as genetic resources for further improvement of cultivated Porphyra strains.

The D1 and D2 proteins of dinoflagellates: unusually accumulated mutations which influence on PSII photoreaction.

Plastid encoded genes of the dinoflagellates are rapidly evolving and most divergent. The importance of unusually accumulated mutations on structure of PSII core protein and photosynthetic function was examined in the dinoflagellates, Symbiodinium sp. and Alexandrium tamarense. Full-length cDNA sequences of psbA (D1 protein) and psbD (D2 protein) were obtained and compared with the other oxygen-evolving photoautotrophs. Twenty-three amino acid positions (7%) for the D1 protein and 34 positions (10%) for the D2 were mutated in the dinoflagellates, although amino acid residues at these positions were conserved in cyanobacteria, the other algae, and plant. Many mutations were likely to distribute in the N-terminus and the D-E interhelical loop of the D1 protein and helix B of D2 protein, while the remaining regions were well conserved. The different structural properties in these mutated regions were supported by hydropathy profiles. The chlorophyll fluorescence kinetics of the dinoflagellates was compared with Synechocystis sp. PCC6803 in relation to the altered protein structure.

Inherited maternal effects on the drought tolerance of a natural hybrid aquatic plant, Potamogeton anguillanus.

We tested whether maternal effects have led to the adaptive divergence of strains of the natural hybrid Potamogeton anguillanus, whose putative parents show contrastingly divergent ecologies. To examine the correlation between phenotypic characters and maternal types, we conducted drought experiments and DNA typing using nuclear and chloroplast genes. In the field, we investigated the distribution of the maternal type along the depth and the inshore-offshore gradient. Hybrids of P. malaianus mothers (M-hybrids) and those of P. perfoliatus mothers (P-hybrids) could not be distinguished morphologically under submerged conditions, but differed in drought tolerance. M-hybrids and P. malaianus formed more terrestrial shoots and exhibited higher survival than P-hybrids and P. perfoliatus in drought experiments. The distribution survey clarified that M-hybrids were dominant in shallow and inshore areas, whereas they were almost absent in deeper and offshore areas. These results indicate that the natural hybrid P. anguillanus differs in adaptive values depending on the maternal type. Bidirectional hybridization and heritable maternal effects may have played important roles in its phenotypic adaptation to local environmental conditions.

Ictal and interictal single photon emission computed tomography in a patient with benign familial infantile convulsions.

Ictal and interictal single photon emission computed tomography (SPECT) and ictal electroencephalography (EEG) were studied in a 3-month-old girl with benign familial infantile convulsions (BFIC) to reveal the epileptic focus. There was bilateral diffuse propagation from a left frontal lobe focus on the ictal EEG. Perfusion in the left frontal region was increased on ictal SPECT and decreased on interictal SPECT. Epileptic foci of BFIC showed the same characteristics as foci of symptomatic partial epilepsy.

Genetic diversity and origin of Potamogeton anguillanus (Potamogetonaceae) in Lake Biwa, Japan.

We analyzed the genetic variation in Potamogeton anguillanus Koidz. and its putative parents, P. malaianus Miq. and P. perfoliatus L., at five allozyme loci of four enzymes to test the hypothesis of a hybrid origin for P. anguillanus, collected in Lake Biwa, Japan. Alleles diagnostic for either P. malaianus or P. perfoliatus were present at four loci. Of 13 single locus phenotypes (SLPs) of P. anguillanus, eight were phenotypes that were expected in F(1) hybrids between P. malaianus and P. perfoliatus. Two SLPs were different from those expected in F(1) hybrids but could have resulted from segregation of parental alleles in later generation hybrids. Each of the remaining three SLPs possessed one allele unique to P. anguillanus. Allozyme analyses thus supported the view that P. anguillanus was derived from hybridization between P. malaianus and P. perfoliatus. It seems likely that the genetic diversity of P. anguillanus found previously originated through multiple hybridizations and sexual processes in P. anguillanus. Other processes such as intragenic recombination, mutation, or hybridization with another lineage are also discussed with reference to the origin of unique alleles.