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Dark-germinated angiosperms develop the chloroplast precursors called etioplasts in cotyledon cells. Etioplasts develop lattice membrane structures called prolamellar bodies (PLBs), where the chlorophyll intermediate protochlorophyllide (Pchlide) forms a ternary complex with NADPH and light-dependent NADPH-Pchlide oxidoreductase (LPOR). The lipid bilayers of etioplast membranes are mainly composed of galactolipids, which play important roles in membrane-associated processes in etioplasts. Although etioplast membranes also contain two anionic lipids, phosphatidylglycerol (PG) and sulfoquinovosyldiacylglycerol (SQDG), the roles of these anionic lipids are unknown. To reveal the importance of PG and SQDG for the development of etioplasts, we characterized etiolated Arabidopsis mutants deficient in the biosynthesis of PG and SQDG. A partial deficiency in PG biosynthesis loosened the lattice structure of PLBs and impaired the insertion of Mg2+into protoporphyrin IX, leading to a significant decrease in Pchlide content. Although a complete lack of SQDG biosynthesis did not notably affect both PLB formation and Pchlide biosynthesis, the lack of SQDG in addition to the partial deficiency of PG caused strong impairments of these processes. The results suggested that PG is required for PLB formation and Pchlide biosynthesis, whereas SQDG plays an auxiliary role in these processes. Notably, the PG deficiency and the lack of SQDG oppositely affected the dynamics of LPOR complexes after photoconversion, suggesting different involvements of PG and SQDG in the organization of LPOR complexes. Our data demonstrate pleiotropic roles of anionic lipids in etioplast development.

DNA is organized into chromatin-like structures, which support the maintenance and regulation of genomes. A unique and poorly understood form of DNA packaging exists in chloroplasts, which are endosymbiotic organelles responsible for photosynthesis. Chloroplast genomes, together with associated proteins, form membraneless structures known as nucleoids. The internal arrangement of the nucleoid, molecular mechanisms of DNA packaging, and connections between nucleoid structure and gene expression remain mostly unknown. We show thatArabidopsis thalianachloroplast nucleoids have a unique organization driven by DNA binding to the thylakoid membranes. DNA associated with the membranes has high protein occupancy, reduced DNA accessibility, and is highly transcribed. In contrast, genes with low levels of transcription are further away from the membranes, have lower protein occupancy, and higher DNA accessibility. Disruption of transcription at specific genes in sigma factor mutants causes a corresponding reduction in membrane association, indicating that RNA polymerase activity causes DNA tethering to the membranes. We propose that transcription organizes the chloroplast nucleoid into a transcriptionally active membrane-associated core and a less active periphery.

Plastids contain their own genomes, which are transcribed by two types of RNA polymerases. One of those enzymes is a bacterial-type, multi-subunit polymerase encoded by the plastid genome. The plastid-encoded RNA polymerase (PEP) is required for efficient expression of genes encoding proteins involved in photosynthesis. Despite the importance of PEP, its DNA binding locations have not been studied on the genome-wide scale at high resolution. We established a highly specific approach to detect the genome-wide pattern of PEP binding to chloroplast DNA using plastid chromatin immunoprecipitation-sequencing (ptChIP-seq). We found that in mature Arabidopsis thaliana chloroplasts, PEP has a complex DNA binding pattern with preferential association at genes encoding rRNA, tRNA, and a subset of photosynthetic proteins. Sigma factors SIG2 and SIG6 strongly impact PEP binding to a subset of tRNA genes and have more moderate effects on PEP binding throughout the rest of the genome. PEP binding is commonly enriched on gene promoters, around transcription start sites. Finally, the levels of PEP binding to DNA are correlated with levels of RNA accumulation, which demonstrates the impact of PEP on chloroplast gene expression. Presented data are available through a publicly available Plastid Genome Visualization Tool (Plavisto) at https://plavisto.mcdb.lsa.umich.edu/.

With implication of developments of plasmonic biochips, we investigated laser trapping of cyanobacteria (CB) on a gold nanostructure, where a nanopyramidal dimer array was integrated. Upon near-inf...

We report the factors governing zero-magnetic-field splitting (zfs) in the lowest-energy electronically excited triplet (T1) states of cyclometalated platinum(II) complexes, whose zfs energies between the lowest- (φ1) and highest-energy spin-sublevels (φ3) in the T1 states (ΔEzfs) are already known: [Pt(bhq)(dpm)] (1Pt), [Pt(thpy)(acac)] (2Pt), [Pt(ppy)(acac)] (3Pt), cis-[Pt(thpy)2 (4Pt), and cis-[Pt(ppy)2] (5Pt), where bhq, dpm, thpy, acac, and ppy are benzo[h]quinoline, dipivaloylmethane, 2-(2-thienyl)pyridine, acetylacetone, and 2-phenylpyridine, respectively. As one of the important findings, we show the relationship between the ΔEzfs and 195Pt NMR chemical shifts of the five Pt(II) complexes. The implications of the ΔEzfs values on the emission properties of the Pt(II) complexes in acetonitrile at 293 K are also discussed. In particular, we demonstrate that the radiative rate constants of the Pt(II) complexes correlate with both ΔEzfs and 195Pt NMR chemical shifts.

Membrane fusion (MF) is one of the most important and ubiquitous processes in living organisms. In this study, we developed a novel method for MF of liposomes. Our method is based on laser-induced bubble generation on gold surfaces (a plasmonic nanostructure or a flat film). It is a simple and quick process that takes about 1 min. Upon bubble generation, liposomes not only collect and become trapped but also fuse to form long tubes beneath the bubble. Moreover, during laser irradiation, these long tubes remain stable and move with a waving motion while continuing to grow, resulting in the creation of ultralong tubes with lengths of about 50 μm. It should be noted that the morphology of these ultralong tubes is analogous to that of a sea anemone. The behavior of the tubes was also monitored by fluorescence microscopy. The generation of these ultralong tubes is discussed on the basis of Marangoni convection and thermophoresis.

Plastids are endosymbiotic organelles containing their own genomes, which are transcribed by two types of RNA polymerases. One of those enzymes is a bacterial-type, multi-subunit polymerase encoded by the plastid genome. The plastid encoded RNA polymerase (PEP) is required for efficient expression of genes encoding proteins involved in photosynthesis. Despite the importance of PEP, its DNA binding locations have not been studied on the genome-wide scale at high resolution. We established a highly specific approach to detect the genome-wide pattern of PEP binding to chloroplasts DNA using ptChIP-seq. We found that in mature Arabidopsis thaliana chloroplasts, PEP has a complex DNA binding pattern with preferential association at genes encoding rRNA, tRNA, and a subset of photosynthetic proteins. Sigma factors SIG2 and SIG6 strongly impact PEP binding to a subset of tRNA genes and have more moderate effects on PEP binding throughout the rest of the genome. PEP binding is commonly enriched on gene promoters, around transcription start sites. Finally, the levels of PEP binding to DNA are correlated with the levels of RNA accumulation, which allowed estimating the quantitative contribution of transcription to RNA accumulation.

Electrochemical reactions in a nano-space are different from those in bulk solutions due to structuring of the liquid molecules and peculiar ion behavior at the electric double layer and are important for applications involving sensors and energy devices. The electrochemical surface forces apparatus (EC-SFA) we developed enabled us to study the electrochemical reactions in a solution nano-confined between the electrodes with varying distance (

Phosphatidylglycerol (PG) is the only major phospholipid in the thylakoid membrane of chloroplasts. PG is essential for photosynthesis, and loss of PG in Arabidopsis thaliana results in severe defects of growth and chloroplast development, with decreased chlorophyll accumulation, impaired thylakoid formation, and down-regulation of photosynthesis-associated genes encoded in nuclear and plastid genomes. However, how the absence of PG affects gene expression and plant growth remains unclear. To elucidate this mechanism, we investigated transcriptional profiles of a PG-deficient Arabidopsis mutant pgp1-2 under various light conditions. Microarray analysis demonstrated that reactive oxygen species (ROS)-responsive genes were up-regulated in pgp1-2. However, ROS production was not enhanced in the mutant even under strong light, indicating limited impacts of photooxidative stress on the defects of pgp1-2. Illumination to dark-adapted pgp1-2 triggered down-regulation of photosynthesis-associated nuclear-encoded genes (PhANGs), while plastid-encoded genes were constantly suppressed. Overexpression of GOLDEN2-LIKE1 (GLK1), a transcription factor gene regulating chloroplast development, in pgp1-2 up-regulated PhANGs but not plastid-encoded genes along with chlorophyll accumulation. Our data suggest a broad impact of PG biosynthesis on nuclear-encoded genes partially via GLK1 and a specific involvement of this lipid in plastid gene expression and plant development.

Etioplasts developed in angiosperm cotyledon cells in darkness rapidly differentiate into chloroplasts with illumination. This process involves dynamic transformation of internal membrane structures from the prolamellar bodies (PLBs) and prothylakoids (PTs) in etioplasts to thylakoid membranes in chloroplasts. Although two galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are predominant lipid constituents of membranes in both etioplasts and chloroplasts, their roles in the structural and functional transformation of internal membranes during etioplast-to-chloroplast differentiation are unknown. We previously reported that a 36% loss of MGDG by an artificial microRNA targeting major MGDG synthase (amiR-MGD1) only slightly affected PLB structures but strongly impaired PT formation and protochlorophyllide biosynthesis. Meanwhile, strong DGDG deficiency in a DGDG synthase mutant (dgd1) disordered the PLB lattice structure in addition to impaired PT development and protochlorophyllide biosynthesis. In this study, thylakoid biogenesis after PLB disassembly with illumination was strongly perturbed by amiR-MGD1. The amiR-MGD1 expression impaired the accumulation of Chl and the major light-harvesting complex II protein (LHCB1), which may inhibit rapid transformation from disassembled PLBs to the thylakoid membrane. As did amiR-MGD1 expression, dgd1 mutation impaired the accumulation of Chl and LHCB1 during etioplast-to-chloroplast differentiation. Furthermore, unlike in amiR-MGD1 seedlings, in dgd1 seedlings, disassembly of PLBs after illumination was retarded. Because DGDG but not MGDG prefers to form the bilayer lipid phase in membranes, the MGDG-to-DGDG ratio may strongly affect the transformation of PLBs to the thylakoid membrane during etioplast-to-chloroplast differentiation.

We report the emission properties of the octahedral hexamolybdenum(II) bromide-core ({Mo6Br8}4+) clusters having a series of terminal aromatic carboxylate ligands (RCOO), [{Mo6Br8}(RCOO)6]2–, in solution and crystalline phases. The acid dissociation constant of RCOOH (pKa(L)) was shown to govern the redox and emission properties of the clusters. Temperature (T)-controlled emission experiments (3–300 K) demonstrated that the clusters showed large T-dependent emission energies (νem) and lifetimes (τem) because of zero-magnetic-field splitting in the emissive excited triplet (T1) states. The spin sublevel (Φn, n = 1–4) model in the T1 state of the cluster explained very well the T-dependent emission characteristics (νem and τem), irrespective of the clusters studied. Furthermore, we revealed that the energy difference between the lowest-energy (Φ1) and energetically upper-lying third (Φ3) or fourth spin sublevels (Φ4), ΔE13 or ΔE14, respectively, correlated very well with pKa(L). The results are discussed ...

Oligothiophene derivatives, which are known as p-type materials, have been synthesized, and their ultrathin layer-by-layer films have been constructed on an electrode using a simple and convenient dipping method. The stepwise deposition behavior of quaterthiophene and sexithiophene derivatives on the electrode via hydrogen bonding was monitored by electronic spectra measurement, and the constructed films were evaluated by X-ray photoelectron spectroscopy, grazing-incidence small-angle X-ray scattering, and cyclic voltammetry. It has been clarified that the constructed layer-by-layer films were electroactive and photoelectroactive.

Porous molecular crystals (PMCs) should function as new-generation functional porous materials, but the selective crystallisation of PMCs is still difficult. Herein we demonstrate that the liquid-liquid interface between the MeOH/H2O mixture and alkanes promotes the crystallisation of a Pt(ii)-based PMC, rather than the nonporous form. This new crystallisation method allows control of not only the porosity but also the luminescence of the Pt(ii) complex crystal.

2,2'-Bipyridine ligands (dsbpys) with dumbbell-like shapes and differently substituted triarylmethyl groups at the C5 and C5' positions showed high ligand performance in the Ni-catalyzed cross-electrophile coupling and the Ni/photoredox-synergistically catalyzed decarboxylative coupling reactions. The superior ligand effects of dsbpys compared to the conventional bpy ligands were attributed to the monochelating nature of dsbpys.

We report the factors governing zero-magnetic-field splitting (zfs) in the lowest-energy electronically excited triplet (T1) states of cyclometalated platinum(ii) complexes, whose zfs energies between the lowest- (φ1) and highest-energy spin-sublevels (φ3) in the T1 states (ΔEzfs) are already known: [Pt(bhq)(dpm)] (1Pt), [Pt(thpy)(acac)] (2Pt), [Pt(ppy)(acac)] (3Pt), cis-[Pt(thpy)2 (4Pt), and cis-[Pt(ppy)2] (5Pt), where bhq, dpm, thpy, acac, and ppy are benzo[h]quinoline, dipivaloylmethane, 2-(2-thienyl)pyridine, acetylacetone, and 2-phenylpyridine, respectively. As one of the important findings, we show the relationship between the ΔEzfs and 195Pt NMR chemical shifts of the five Pt(ii) complexes. The implications of the ΔEzfs values on the emission properties of the Pt(ii) complexes in acetonitrile at 293 K are also discussed. In particular, we demonstrate that the radiative rate constants of the Pt(ii) complexes correlate with both ΔEzfs and 195Pt NMR chemical shifts.

Tricyanidonitridorhenium(V) complexes with 2,2'-bipyridine (bpy) derivatives in which the 4 and 4' positions were substituted by X, [ReN(CN)3(X2bpy)]- (X = NMe2, NH2, OMe, Me, Cl, and Br), were newly synthesized and characterized. The structures of the new complexes were determined by single-crystal X-ray analysis. UV-vis spectra of the complexes in dimethyl sulfoxide (DMSO) showed that the peak maximum wavelengths of rhenium-to-π* bpy-type-ligand charge transfer were in the range of 474-542 nm. Cyclic voltammograms in n-(C4H9)4NPF6-DMSO showed one-electron oxidation and reduction waves corresponding to the Re(VI/V) and X2bpy0/- processes, respectively. The new complexes and [ReN(CN)3bpy]- showed photoluminescence in the crystalline phase at 295 and 80 K and in DMSO at 295 K. The origin of the emission in DMSO was attributed to the triplet nature of the rhenium-to-π* bpy-type-ligand charge-transfer transition. Density functional theory calculations showed that the highest occupied and lowest unoccupied molecular orbitals were primarily localized on the dxy orbital of the rhenium and π* orbitals of the bpy-type ligand, respectively.

RNase H1 is an endonuclease specific toward the RNA strand of RNA:DNA hybrids. Members of this protein family are present in most living organisms and are essential for removing RNA that base pairs with DNA. It prevents detrimental effects of RNA:DNA hybrids and is involved in several biological processes. Arabidopsis thaliana has been previously shown to contain three genes encoding RNase H1 proteins that localize to three distinct cellular compartments. We show that these genes originate from two gene duplication events. One occurred in the common ancestor of dicots and produced nuclear and organellar RNase H1 paralogs. Second duplication occurred in the common ancestor of Brassicaceae and produced mitochondrial- and plastid-localized proteins. These proteins have the canonical RNase H1 activity, which requires at least four ribonucleotides for endonucleolytic digestion. Analysis of mutants in the RNase H1 genes revealed that the nuclear RNH1A and mitochondrial RNH1B are dispensable for development under normal growth conditions. However, the presence of at least one organellar RNase H1 (RNH1B or RNH1C) is required for embryonic development. The plastid-localized RNH1C affects plastid DNA copy number and sensitivity to replicative stress. Our results present the evolutionary history of RNH1 proteins in A. thaliana, demonstrate their canonical RNase H1 activity and indicate their role in early embryonic development.

The temperature (T) dependences of the emissions from the tetra-n-butylammonium salts of [{Mo6X8}Y6]2– (X, Y = Cl, Br, and I) in optically transparent polyethylene glycol dimethacrylate matrixes were studied in the T range of 3–300 K. [{Mo6Cl8}Y6]2–, [{Mo6Br8}Y6]2–, and [{Mo6I8}I6]2– showed the T-dependent emission characteristics similar to those of other hexanuclear Mo(II), Re(III), and W(II) clusters reported previously, while [{Mo6I8}Br6]2– and [{Mo6I8}Cl6]2– exhibited the emission properties different from those of other [{Mo6X8}Y6]2– clusters. The photophysical behavior of these clusters was explained by the excited triplet state spin-sublevel (Φn, n = 1–4) model irrespective of the nature of X and Y. The zero-magnetic-field splitting energies between the lowest energy (Φ1) and the higher energy spin sublevels (Φ4 or Φ3) caused by the first- or second-order spin–orbit coupling, ΔE14 or ΔE13, were evaluated to be 620–870 or 50–99 cm–1, respectively. We found the linear correlation between the ΔE14 or...

Novel heteroleptic arylborane–ruthenium(II) complexes having a series of ancillary ligands L′ ([Ru(B2bpy)L′2]2+) in CH3CN showed low-energy/intense metal-to-ligand charge transfer (MLCT)-type absorption and intense/long-lived emission compared to the reference complexes. The spectroscopic and photophysical properties of [Ru(B2bpy)L′2]2+ were shown to be manipulated synthetically by the electron-donating ability of the ancillary ligand(s). The intense and long-lived emission observed for [Ru(B2bpy)L′2]2+ in CH3CN at 298 K is responsible for the accelerated radiative and decelerated nonradiative decay processes, which are controllable through the electronic structures of the ancillary ligand(s). On the basis of the present systematic study, furthermore, we succeeded in demonstrating the Strickler–Berg-type relation between the molar absorption coefficients of the MLCT bands and the radiative rate constants of the complexes.

We report a systematic study on the redox, spectroscopic, and photophysical properties of a series of [{Mo6X8}Y6]2- (X, Y = Cl, Br, or I. 1-9). All of the [{Mo6X8}Y6]2- clusters show intense and long-lived phosphorescence in both CH3CN and crystalline phases at 298 K. We found that the emission quantum yields (Φem) of 1-9 increase in the sequences X = Cl < Br < I and Y = I < Br < Cl for given Y and X, respectively. The emission lifetimes (τem) of the clusters also increase in the sequence Y = I < Br < Cl for given {Mo6X8}4+-core clusters. The present data demonstrate that arbitrary combinations of X and Y in [{Mo6X8}Y6]2- could tune τem and Φem in the ranges of 85-300 μs and 0.09-0.47, respectively. Both capping (X) and terminal ligand (Y) effects on the photophysical properties of the clusters are discussed on the basis of the energy gap (i.e., emission energy) dependence of the nonradiative decay rate constant.

The starburst-type arylborane-appended polypyridyl RuII complex [Ru{4,7-bis({dimesityl}boryldurylethynyl)-1,10-phenanthroline}3]2+ (1) was synthesized, and its spectroscopic and photophysical properties were evaluated. In the excited state of the complex, intramolecular charge transfer (CT) between the π orbital of the aryl group and the vacant p orbital of the boron atom [π(aryl)–p(B) CT] interacts synergistically with metal-to-ligand charge transfer (MLCT). The synergistic CT interactions in 1 are more effective than those in previously reported arylborane-appended polypyridyl RuII complexes and lead to bright (molar absorption coefficient of the MLCT band = 7.2 × 104 m–1 cm–1, emission quantum yield = 0.29) and long-lived emission (8.7 µs) of 1 in CH3CN at 298 K. The unique emission characteristics of 1 are discussed in detail together with its electrochemical properties and time-dependent DFT (TD-DFT) calculations.

Cotyledon cells of dark-germinated angiosperms develop etioplasts that are plastids containing unique internal membranes called prolamellar bodies (PLBs). Protochlorophyllide (Pchlide), a precursor of chlorophyll, accumulates in PLBs and forms a ternary complex with NADPH and light-dependent NADPH:protochlorophyllide oxidoreductase (LPOR), which allows for the rapid formation of chlorophyll after illumination while avoiding photodamage. PLBs are 3D lattice structures formed by the lipid bilayer rich in monogalactosyldiacylglycerol (MGDG). Although MGDG was found to be required for the formation and function of the thylakoid membrane in chloroplasts in various plants, the roles of MGDG in PLB formation and etioplast development are largely unknown. To analyze the roles of MGDG in etioplast development, we suppressed MGD1 encoding the major isoform of MGDG synthase by using a dexamethasone-inducible artificial microRNA in etiolated Arabidopsis (Arabidopsis thaliana) seedlings. Strong MGD1 suppression caused a 36% loss of MGDG in etiolated seedlings, together with a 41% decrease in total Pchlide content. The loss of MGDG perturbed etioplast membrane structures and impaired the formation of the photoactive Pchlide-LPOR-NADPH complex and its oligomerization, without affecting LPOR accumulation. The MGD1 suppression also impaired the formation of Pchlide from protoporphyrin IX via multiple enzymatic reactions in etioplast membranes, which suggests that MGDG is required for the membrane-associated processes in the Pchlide biosynthesis pathway. Suppressing MGD1 at several germination stages revealed that MGDG biosynthesis at an early germination stage is particularly important for Pchlide accumulation. MGDG biosynthesis may provide a lipid matrix for Pchlide biosynthesis and the formation of Pchlide-LPOR complexes as an initial step of etioplast development.

We demonstrate the simultaneous formation and spatial patterning of ZnO nanocrystals on an indium–tin oxide (ITO) surface upon local heating using a laser (1064 nm) and subsequent formation of microbubbles. Laser irradiation of an ITO surface in aqueous [Zn(NH3)4]2+ solution (1.0 × 10–2 M at pH 12.0) under an optical microscope produced ZnO nanocrystals, the presence of which was confirmed by X-ray diffraction analysis and Raman microspectroscopy. Scanning the focused laser beam over the ITO surface generated a spatial ZnO pattern (height: ∼60 nm, width: ∼1 μm) in the absence of a template or mask. The Marangoni convection generated in the vicinity of the microbubbles resulted in a rapid concentration/accumulation of [Zn(NH3)4]2+ around the microbubbles, which led to the formation of ZnO at the solid–bubble–solution three-phase contact line around the bubbles and thus afforded ZnO nanocrystals on the ITO surface upon local heating with a laser.

A novel sensor, 4-[2-(9-anthryl)ethynyl]-1,10-phenanthroline (1), exhibits highly intense fluorescent in the wavelength region of 440-600 nm (maximum wavelength (λf) = 470 nm) with the quantum yield (Φf) and lifetime (τf) being 0.90 and 4.2 ns, respectively, in CH3CN at 298 K. In the presence of a divalent cation (M2+ = Ba2+, Ca2+, Mg2+, or Zn2+) in CH3CN, sensor 1 can tightly bind M2+ and shows intense fluorescent (Φf = 0.90-0.19, τf = 2.1-6.9 ns) with the color being dependent on the nature of M2+ (λf = 514-584 nm). The results demonstrate that a single fluorescent sensor 1 is capable of simultaneous identification and quantitation of M2+ based on λf and the fluorescent intensity (Φf), respectively. The fluorescence maximum energy of the [1-M2+] complex is shown to correlate linearly with the pKa value of M2+. The spectroscopic and photophysical properties of sensor 1 in the absence and presence of M2+ are also discussed.

New octahedral hexamolybdenum(II) bromide clusters, the tetra-n-butylammonium (n-Bu4N+) salts of [{Mo6Br8}L 6]2− with a series of aliphatic and aromatic carboxylates (L) having different pK a values (pK a(L) = 1.75–5.03), were synthesized and characterized by X-ray single-crystal diffraction analysis, cyclic/differential pulse voltammetries, and emission spectroscopy, together with two new hexamolybdenum(II) iodide clusters: (n-Bu4N)2[{Mo6I8}L 6] (L = 3,5-dimethylbenzoate or perfluorobenzoate). In the present study, we successfully demonstrated that the average bond length between the Mo atom and the ligating O atom in L, the redox potentials (in acetone), and the emission parameters (maximum energy, quantum yield, and lifetime in acetone) of these complexes and previously reported (n-Bu4N)2[{Mo6I8}L 6] clusters correlated almost linearly with pK a(L) for a series of the bromide or iodide clusters. The nature of the inner capping ligand (X = Br or I) also governed the structural, redox, and emission properties of the cluster complexes. The origins of such pK a(L) and inner capping ligand dependences of these properties are discussed in detail.

Metallic nanogap dimers are extremely useful for enhancing surface-enhanced Raman scattering and various nonlinear optical effects employing near-field enhancement effects induced by the localized surface plasmon resonance. However, the metallic nanogap dimers exhibit an intense light scattering due to the strong dipole-dipole interaction between two metallic nanostructures and, therefore, are not necessarily a structural design that exhibits the highest near-field enhancement due to the radiation loss. Here, we propose further enhancement of the near-field on metallic nanogap dimers using quasi-dark plasmon modes. By coupling with gold (Au) nanorods having the same plasmon resonant wavelength, but completely different sizes, a quasi-dark plasmon mode, which reduces the radiation loss slightly, is induced, resulting in the elongation of the plasmon dephasing time. As a result, the signal of surface-enhanced Raman scattering of crystal violet molecules adsorbed on the Au nanogap dimer is enhanced up to about three times as compared to that measured using the Au nanogap dimer without the Au nanorods. Scattering spectrum measurements as well as electromagnetic simulations were performed to clarify the mechanism for further enhancement of the near-field. The proposed coupled plasmonic system is expected to be advantageous, especially in enhancing nonlinear optical effects using plasmonic enhancement effects.

The temperature ( T) dependences of the emissions from the tetra- n-butylammonium salts of [{Mo

Since the time DNA was discovered as the code of life, genetic analysis has greatly advanced our understanding of the relation between genotype and phenotype and associated molecular mechanisms in various organisms including plants and algae. Forward genetics from phenotype to genotype has identified causal genes of interesting phenotypes induced by chemical, ionizing-radiation, or DNA insertional mutagenesis. Meanwhile, reverse genetics from genotype to phenotype has revealed physiological and molecular roles of known gene sequences. During the past dozen years, many molecular genetic tools have been developed to investigate gene functions quickly and efficiently. In this chapter, we introduce several approaches of forward and reverse genetics, including random chemical and DNA insertional mutagenesis, activation tagging, RNA interference, and gene overexpression and induction systems, with some examples of genetic studies of chloroplast biology mainly in Arabidopsis thaliana. We also briefly describe methods for chemical and DNA insertion mutagenesis and how to obtain sequence-tagged mutants from public collections. With greatly improved DNA sequencing and genome-editing technologies, model organisms as well as diverse species can be used for molecular biology. Genetic analysis can play an increasingly important role in elucidating chloroplast biogenesis and functions.

Angiosperms germinated in the dark develop etioplasts, the chloroplast precursors, in cotyledon cells. Etioplasts contain lattice membrane structures called prolamellar bodies (PLBs) and lamellar prothylakoids as internal membrane systems. PLBs accumulate the chlorophyll intermediate protochlorophyllide (Pchlide) in a complex with NADPH and light-dependent NADPH:Pchlide oxidoreductase (LPOR). Two galactolipids, monogalactosyldiacylglycerol and digalactosyldiacylglycerol (DGDG), are major constituents of etioplast membranes. We previously reported that monogalactosyldiacylglycerol facilitates the synthesis of Pchlide and the formation of the Pchlide-LPOR-NADPH complex in etioplasts, but the importance of DGDG in etioplasts is still unknown. To determine the role of DGDG in etioplast development and functions, we characterized a knockout mutant (dgd1) of Arabidopsis (Arabidopsis thaliana) DGD1, which encodes the major isoform of DGDG synthase, in the etioplast development stage. In etiolated dgd1 seedlings, DGDG content decreased to 20% of the wild-type level, the lattice structure of PLBs was disordered, and the development of prothylakoids was impaired. In addition, membrane-associated processes of Pchlide biosynthesis, formation of the Pchlide-LPOR-NADPH complex, and dissociation of the complex after the photoconversion of Pchlide to chlorophyllide were impaired in dgd1, although the photoconversion reaction by LPOR was not affected by the DGDG deficiency. Total carotenoid content also decreased in etiolated dgd1 seedlings, but the carotenoid composition was unchanged. Our data demonstrate a deep involvement of DGDG in the formation of the internal membrane structures in etioplasts as well as in membrane-associated processes of pigment biosynthesis and pigment-protein complex organization.

Since the time DNA was discovered as the code of life, genetic analysis has greatly advanced our understanding of the relation between genotype and phenotype and associated molecular mechanisms in various organisms including plants and algae. Forward genetics from phenotype to genotype has identified causal genes of interesting phenotypes induced by chemical, ionizing-radiation, or DNA insertional mutagenesis. Meanwhile, reverse genetics from genotype to phenotype has revealed physiological and molecular roles of known gene sequences. During the past dozen years, many molecular genetic tools have been developed to investigate gene functions quickly and efficiently. In this chapter, we introduce several approaches of forward and reverse genetics, including random chemical and DNA insertional mutagenesis, activation tagging, RNA interference, and gene overexpression and induction systems, with some examples of genetic studies of chloroplast biology mainly in Arabidopsis thaliana. We also briefly describe methods for chemical and DNA insertion mutagenesis and how to obtain sequence-tagged mutants from public collections. With greatly improved DNA sequencing and genome-editing technologies, model organisms as well as diverse species can be used for molecular biology. Genetic analysis can play an increasingly important role in elucidating chloroplast biogenesis and functions.

We report a systematic study on the redox, spectroscopic, and photophysical properties of a series of [{Mo

Monogalactosyldiacylglycerol (MGDG) is the major lipid constituent of thylakoid membranes and is essential for chloroplast biogenesis in plants. In Arabidopsis (Arabidopsis thaliana), MGDG is predominantly synthesized by inner envelope-localized MONOGALACTOSYLDIACYLGLYCEROL SYNTHASE1 (MGD1); its knockout causes albino seedlings. Because of the lethal phenotype of the null MGD1 mutant, functional details of MGDG synthesis at seedling development have remained elusive. In this study, we used an inducible gene-suppression system to investigate the impact of MGDG synthesis on cotyledon development. We created transgenic Arabidopsis lines that express an artificial microRNA targeting MGD1 (amiR-MGD1) under the control of a dexamethasone-inducible promoter. The induction of amiR-MGD1 resulted in up to 75% suppression of MGD1 expression, although the resulting phenotypes related to chloroplast development were diverse, even within a line. The strong MGD1 suppression by continuous dexamethasone treatment caused substantial decreases in galactolipid content in cotyledons, leading to severe defects in the formation of thylakoid membranes and impaired photosynthetic electron transport. Time-course analyses of the MGD1 suppression during seedling germination revealed that MGDG synthesis at the very early germination stage is particularly important for chloroplast biogenesis. The MGD1 suppression down-regulated genes associated with the photorespiratory pathway in peroxisomes and mitochondria as well as those responsible for photosynthesis in chloroplasts and caused high expression of genes for the glyoxylate cycle. MGD1 function may link galactolipid synthesis with the coordinated transcriptional regulation of chloroplasts and other organelles during cotyledon greening.

A four-electron-reduced ruthenium(II) NADH-type complex, [Ru(bbnpH4)(CO)2Cl](PF6) (bbnpH4 = 2,2′-(4-(tert-butyl)pyridine-2,6-diyl)bis(5,10-dihydrobenzo[b][1,5]naphthyridine)), has been successfully synthesized by mixing an NAD+-type ligand, bbnp (bbnp = 2,2′-(4-(tert-butyl)pyridine-2,6-diyl)bis(benzo[b][1,5]naphthyridine)), and [Ru(CO)2Cl2] under moderate water-gas-shift reaction conditions, which has been fully characterized by single-crystal X-ray structure analysis, ESI-TOF mass spectrometry, and NMR spectroscopy.

We report for the first time quasi-one-step six-electron electrochemical reduction of a new hexanuclear molybdenum(II) bromide cluster having terminal 3,5-dinitrobenzoate ligands: [Mo6Br8(DNBA)6]2–. The electrochemical responses of the cluster were studied based on cyclic (CV), differential pulse, and normal pulse voltammetries, together with the analytical simulations of the CV and spectroelectrochemistry. CV simulations have revealed that the electrochemical reaction of the cluster proceeds in an EEEEEE scheme, and the potential differences between the two adjacent reduction steps are in the range of 15–30 mV. These potential differences indicate quite smooth and quasi-one-step six-electron reduction of the cluster.

The development of plant chloroplasts is regulated by various developmental, environmental, and hormonal cues. In Arabidopsis (Arabidopsis thaliana), chloroplast development is repressed in roots via auxin signaling. However, roots develop chloroplasts when they are detached from the shoot. In contrast to auxin, cytokinin positively affects chloroplast development in roots, but the role and signaling pathway of cytokinin in the root greening response remain unclear. To understand the regulatory pathways of chloroplast development in the plant stress response, we examined the mechanisms underlying the conditional greening of detached roots. In wild-type Arabidopsis roots, shoot removal activates type B ARABIDOPSIS RESPONSE REGULATOR (ARR)-mediated cytokinin signaling and induces chlorophyll accumulation and photosynthetic remodeling. ARR1 and ARR12 are essential for up-regulating nucleus- and plastid-encoded genes associated with chloroplast development in detached roots. In this process, WOUND INDUCED DEDIFFERENTIATION1 and class B GATA transcription factors (B-GATAs) act upstream and downstream of ARRs, respectively. Overexpression of B-GATAs promotes root greening, as does shoot removal, dependent on a light signaling transcription factor, LONG HYPOCOTYL5. Auxin represses the root greening response independent of ARR signaling. GNC-LIKE (GNL), a B-GATA, is strongly up-regulated in detached roots via ARR1 and ARR12 but is repressed by auxin, so GNL may function at the point of convergence of cytokinin and auxin signaling in the root greening response.

In this study, we developed a well-of-the-well (WOW) system-based embryo culture plate with an oxygen sensing photoluminescent probe (OSPP). This system can incubate single embryos in an array of microwells and continuously and non-invasively monitor their morphology by microscopy and respiration metabolic activity based on the quenching of photoexcited platinum octaethylporphyrin by oxygen. Although the development rate to the blastocyst stage obtained in the WOW embryo culture plate with the OSPP was about 11% lower than that obtained with the conventional drop culture method because of the absence of paracrine effects due to the size of the microwells, the average cell number in the embryo at the blastocyst stage was not significantly different between the two culture systems. However, the present embryo culture plate enabled the selection and harvest of high quality blastocysts by monitoring both their morphology and their oxygen consumption rate, making it suitable for the high throughput evaluation of embryos.

We have developed a new fabrication method for a ring structure of assembled nanoparticles on a gold surface by the use of continuous Nd:YAG laser light. A micronanobubble on a gold surface, created by laser local heating, acts as a template for the formation of the ring structure. Both Marangoni convection flow and capillary flow around the micronanobubble are responsible for the driving force to assemble nanoparticles such as CdSe Q-dots into the ring structure from the solution. Because a single micronanobubble was generated by the Nd:YAG laser focusing point, the precise positioning of the ring structure was feasible directly on the gold surface, which makes it possible to fabricate various patterns of rings such as arrays and letters and even a double-ring structure without any photomasks or any templates.

With phosphate deficiency, the role of phosphatidylglycerol is compensated by increased glycolipid content in thylakoid membrane biogenesis but not photosynthetic electron transport in Arabidopsis chloroplasts. In plants and cyanobacteria, anionic phosphatidylglycerol (PG) is the only major phospholipid in thylakoid membranes, where neutral galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are predominant. In addition to provide a lipid bilayer matrix, PG plays a specific role in photosynthetic electron transport. Non-phosphorous sulfoquinovosyldiacylglycerol (SQDG) is another anionic lipid in thylakoids; it substitutes for PG under phosphate (Pi) deficiency to maintain proper balance of anionic charge in thylakoid membranes. Although the crucial role of PG in photosynthesis has been deeply analyzed in cyanobacteria, its physiological function in seed plants other than photosynthesis remains unclear. To reveal specific roles of PG and functional overlaps with other thylakoid lipids, we characterized a PG-deficient Arabidopsis mutant (pgp1-2) under Pi-controlled conditions. Under Pi-sufficient conditions, the proportion of PG and other thylakoid lipids was decreased in pgp1-2, which led to severe disruption of thylakoid membrane biogenesis. Under Pi-deficient conditions, the proportion of all glycolipids in the mutant was greatly increased, with that of PG further decreased. In Pi-deficient pgp1-2, thylakoid membranes remarkably developed, which was accompanied by a change in nucleoid morphology and restored expression of nuclear- and plastid-encoded photosynthesis genes. Increase in glycolipid content with Pi deficiency may compensate for the loss of PG in terms of thylakoid membrane biogenesis. Although Pi deficiency increased chlorophyll and photosynthesis protein content in pgp1-2, it critically decreased photochemical activity in PSII. Further deprivation of PG in photosynthesis complexes may abolish the PSII activity in Pi-deficient pgp1-2, which suggests that glycolipids cannot replace PG in photosynthesis.

We have developed a novel laser-induced crystallization method utilizing local heat-induced bubble/water interface. Continuous laser beam of 1064 nm is focused on a gold nanoparticles thin film surface covered with glycine supersaturated aqueous solution. Light absorption of the film due to localized plasmon resonance caused local heating at the focal position and produced a single thermal vapor microbubble, which generated thermal gradient followed by convection flow around the bubble and eventually induced glycine crystallization and growth. The crystallization mechanism is discussed by considering gathering and accumulating molecules around the bubble/water interface assisted by convection flow and temperature jump.