Oil body-mediated defense against fungi: From tissues to ecology

Oil bodies are localized in the seed cells and leaf cells of many land plants. They have a passive function as storage organelles for lipids. We recently reported that the leaf oil body has an active function as a subcellular factory that produces an antifungal oxylipin during fungal infection in Arabidopsis thaliana. Here, we propose a model for oil body-mediated plant defense. Remarkably, senescent leaves develop oil bodies and accumulate α-dioxygenase1 (α-DOX1) and caleosin3 (CLO3) on the oil-body membrane, which catalyze the conversion of α-linolenic acid to the phytoalexin 2-hydroxy-octadecatrienoic acid (2-HOT). The model proposes that senescent leaves actively produce antifungal oxylipins and phytoalexins, and abscised leaves contain a mixture of antifungal compounds. In natural settings, the abscised leaves with antifungal compounds accumulate in leaf litter and function to protect healthy tissues and young plants from fungal infection. Plants might have evolved this ecological function for dead leaves.     

Chondroitin sulfate proteoglycans from salmon nasal cartilage inhibit angiogenesis

Because cartilage lacks nerves, blood vessels, and lymphatic vessels, it is thought to contain factors that inhibit the growth and development of those tissues. Chondroitin sulfate proteoglycans (CSPGs) are a major extracellular component in cartilage. CSPGs contribute to joint flexibility and regulate extracellular signaling via their attached glycosaminoglycan, chondroitin sulfate (CS). CS and CSPG inhibit axonal regeneration; however, their role in blood vessel formation is largely unknown. To clarify the function of CSPG in blood vessel formation, we tested salmon nasal cartilage proteoglycan (PG), a member of the aggrecan family of CSPG, for endothelial capillary-like tube formation. Treatment with salmon PG inhibited endothelial cell adhesion and in vitro tube formation. The anti-angiogenic activity was derived from CS in the salmon PG but not the core protein. Salmon PG also reduced matrix metalloproteinase expression and inhibited angiogenesis in the chick chorioallantoic membrane. All of these data support an anti-angiogenic role for CSPG in cartilage.     

Myrosin Cell Development Is Regulated by Endocytosis Machinery and PIN1 Polarity in Leaf Primordia of Arabidopsis thaliana

Myrosin cells, which accumulate myrosinase to produce toxic compounds when they are ruptured by herbivores, form specifically along leaf veins in Arabidopsis thaliana. However, the mechanism underlying this pattern formation is unknown. Here, we show that myrosin cell development requires the endocytosis-mediated polar localization of the auxin-efflux carrier PIN1 in leaf primordia. Defects in the endocytic/vacuolar SNAREs (syp22 and syp22 vti11) enhanced myrosin cell development. The syp22 phenotype was rescued by expressing SYP22 under the control of the PIN1 promoter. Additionally, myrosin cell development was enhanced either by lacking the activator of endocytic/vacuolar RAB5 GTPase (VPS9A) or by PIN1 promoter-driven expression of a dominant-negative form of RAB5 GTPase (ARA7). By contrast, myrosin cell development was not affected by deficiencies of vacuolar trafficking factors, including the vacuolar sorting receptor VSR1 and the retromer components VPS29 and VPS35, suggesting that endocytic pathway rather than vacuolar trafficking pathway is important for myrosin cell development. The phosphomimic PIN1 variant (PIN1-Asp), which is unable to be polarized, caused myrosin cells to form not only along leaf vein but also in the intervein leaf area. We propose that Brassicales plants might arrange myrosin cells near vascular cells in order to protect the flux of nutrients and water via polar PIN1 localization.     

Active-Site Structure of the Thermophilic Foc-Subunit Ring in Membranes Elucidated by Solid-State NMR

F_oF₁-ATP synthase uses the electrochemical potential across membranes or ATP hydrolysis to rotate the F_oc-subunit ring. To elucidate the underlying mechanism, we carried out a structural analysis focused on the active site of the thermophilic c-subunit (TF_oc) ring in membranes with a solid-state NMR method developed for this purpose. We used stereo-array isotope labeling (SAIL) with a cell-free system to highlight the target. TF_oc oligomers were purified using a virtual ring His tag. The membrane-reconstituted TF_oc oligomer was confirmed to be a ring indistinguishable from that expressed in E. coli on the basis of the H⁺-translocation activity and high-speed atomic force microscopic images. For the analysis of the active site, 2D ¹³C-¹³C correlation spectra of TF_oc rings labeled with SAIL-Glu and -Asn were recorded. Complete signal assignment could be performed with the aid of the C^α_i+1-C^α_i correlation spectrum of specifically ¹³C,¹⁵N-labeled TF_oc rings. The C^δ chemical shift of Glu-56, which is essential for H⁺ translocation, and related crosspeaks revealed that its carboxyl group is protonated in the membrane, forming the H⁺-locked conformation with Asn-23. The chemical shift of Asp-61 C^γ of the E. coli c ring indicated an involvement of a water molecule in the H⁺ locking, in contrast to the involvement of Asn-23 in the TF_oc ring, suggesting two different means of proton storage in the c rings.     

Cytotoxic action of bisabololoxide A of German chamomile on human leukemia K562 cells in combination with 5-fluorouracil

German chamomile (Matricaria recutita L.) is a popular ingredient in herbal teas. In previous study, micromolar bisabololoxide A, one of main constituents in German chamomile, exerted cytotoxic action on rat thymocyte, a normal non-proliferative cell. This result prompted us to study the effect of bisabololoxide A on proliferative cancer cells and to seek the possibility of its use with 5-fluorouracil, an anticancer agent. In this study, the effect of micromolar bisabololoxide A on human leukemia K562 cells was cytometrically examined. Although the incubation of K562 cells with 10 μM bisabololoxide A for 72 h did not significantly increase the percentage populations of dead cells and shrunken cells, the inhibitory action on the growth was obviously observed. It was not the case for the concentrations of less than 5 μM. The threshold concentration of bisabololoxide A to exert the cytotoxic action on K562 cells was ascertained to be 5-10 μM. Bisabololoxide A at 5-10 μM did not exert cytotoxic action on normal non-proliferative cells (rat thymocytes) in our previous study. Since the antiproliferative action of micromolar bisabololoxide A on cancerous cells was expected to be beneficial to cancer treatment, the modification of antiproliferative action of 5-fluorouracil (3-30 μM) by bisabololoxide A was studied. The combination of 5-fluorouracil and bisabololoxide further inhibited the growth of K562 cells although the additive inhibition of growth by bisabololoxide A became smaller as the concentration of 5-fluorouracil increased. Therefore, it is suggested that the simultaneous application of German chamomile containing bisabololoxide A may reduce the dose of 5-fluorouracil.     

Regulation of the plastochron by three many-noded dwarf genes in barley

The plastochron, the time interval between the formation of two successive leaves, is an important determinant of plant architecture. We genetically and phenotypically investigated many-noded dwarf (mnd) mutants in barley. The mnd mutants exhibited a shortened plastochron and a decreased leaf blade length, and resembled previously reported plastochron1 (pla1), pla2, and pla3 mutants in rice. In addition, the maturation of mnd leaves was accelerated, similar to pla mutants in rice. Several barley mnd alleles were derived from three genes—MND1, MND4, and MND8. Although MND4 coincided with a cytochrome P450 family gene that is a homolog of rice PLA1, we clarified that MND1 and MND8 encode an N-acetyltransferase-like protein and a MATE transporter-family protein, which are respectively orthologs of rice GW6a and maize BIGE1 and unrelated to PLA2 or PLA3. Expression analyses of the three MND genes revealed that MND1 and MND4 were expressed in limited regions of the shoot apical meristem and leaf primordia, but MND8 did not exhibit a specific expression pattern around the shoot apex. In addition, the expression levels of the three genes were interdependent among the various mutant backgrounds. Genetic analyses using the double mutants mnd4mnd8 and mnd1mnd8 indicated that MND1 and MND4 regulate the plastochron independently of MND8, suggesting that the plastochron in barley is controlled by multiple genetic pathways involving MND1, MND4, and MND8. Correlation analysis between leaf number and leaf blade length indicated that both traits exhibited a strong negative association among different genetic backgrounds but not in the same genetic background. We propose that MND genes function in the regulation of the plastochron and leaf growth and revealed conserved and diverse aspects of plastochron regulation via comparative analysis of barley and rice.     

Small GTP-Binding Proteins are Associated with the Vesicles That are Targeted to Vacuoles in Developing Pumpkin Cotyledons

Dense vesicles mediate the final step in the delivery of seedproteins to vacuoles in developing pumpkin (Cucurbita sp.) cotyledons.To explore the vesicle-mediated transport system that is targetedto vacuoles in plant cells, we isolated the dense vesicles andexamined then for the presence of guanine nucleotide-bindingproteins. GTP-binding proteins of 25 kDa and 27 kDa were detectedon the isolated vesicles. The 25-kDa protein had dithiothreitol-dependentGTP-binding activity, but binding of GTP by the 27-kDa proteinshowed no such dependence. Binding of [     

Validation of daily surface water depth model of the Greater Everglades based on real-time stage monitoring and aerial ground elevation survey

As part of the Everglades Depth Estimation Network (EDEN) project, this paper describes validation of raster-based daily surface water depth models of the Greater Everglades in Florida developed using real-time stage data and elevation data obtained from a survey with an aerial height finder. Daily median stage data obtained at over 200 locations were interpolated using the multiquadric radial basis function. Surface water depth was obtained by subtracting a digital elevation model from the interpolated stage raster. The model was validated with 751 independent field measurements of surface water depth between 1999 and 2004. Correlations between prediction error and both density of the monitoring gages and distance from a major linear geographic feature, such as a canal, were weak, suggesting that the error does not depend on these features. South Florida has distinct dry and wet seasons and the study area is dominated by sawgrass and wet prairie. Seasonality and ground vegetation type significantly affect prediction error. Correlation between observed and predicted water depth was high for all combination of season and vegetation type (0.83–0.96). Model validation using an equivalence test provided evidence of equivalence between predicted and observed water depths in dry season prairie-dominated and wet season sawgrass-dominated areas with the strict test and in dry season sawgrass-dominated areas with the liberal test, but not in wet season prairie-dominated areas. Equivalence between observed and predicted water depth for both dry season sawgrass- and wet season prairie-dominated areas were confirmed with the strict test after further model calibrations using linear regressions.     

MIS 21 and the Mid-Pleistocene climate transition: Climate and sea-level variation from a sediment core in Osaka Bay,Japan

We report climate and sea-level variation for the marine oxygen isotope stage (MIS) 21, encompassing the end of the Mid-Pleistocene climate transition (MPT), based on pollen, diatom, and sulfur records from a 50-m thick sequence in a core from Osaka Bay. An extremely warm climate coincided with the sea level highstand of substage 21.5, when the warm-temperate element Quercus (Cyclobalanopsis) exceeds 40% of total arboreal pollen. This was followed by a warm-temperate to temperate and humid climate that continued until the end of MIS 21. A linear age model shows that climate was dominated by precessional cyclicity, with an inverse correlation between temperature and precipitation. The postglacial sea-level rise reached its highest peak in substage 21.5, when paleo-Osaka Bay reached its maximum extent including Kyoto and Nara Basins. At this time pelagic diatoms were dominant in the central part of the bay. Sea level dropped below the Osaka Bay sill (about ? 60 m at present) during substage 21.4, followed by a rise above the sill in substage 21.3, and a drop at 21.2. Sea level remained below the sill during substage 21.1. The thermal maximum and sea level peak occurred just after the rapid postglacial sea level rise, after which there was a gradual decline in temperature and sea level accompanied by precession-related oscillations; these features are typical of the post-MPT interglacials dominated by 100-ka cyclicity. These features may be a sign of termination of the MPT.     

Variation inSclerotium rolfsii isolates in Japan

Sixty-seven isolates of the southern blight fungus from Japan were divided into five groups based on ITS-RFLP analysis of nuclear rDNA. Morphological characters of sclerotia varied between groups. Three groups were reidentified asSclerotium rolfsii, and two resembledS. delphinii in RFLP patterns and/or in having large sclerotia and relatively low optimal growth temperature (28°C). Sclerotia of the latter, however, varied in size according to temperature and became indistinguishable from those ofS. rolfsii at high temperatures. Hyphal anastomosis (imperfect fusion) was observed between different ITS-RFLP groups, as well as between different isolates belonging to the same groups. These results indicate that populations of this fungus in Japan consists of several different subgroups, although morphological differences are not always evident.