Phototropin‐ and photosynthesis‐dependent mitochondrial positioning in Arabidopsis thaliana mesophyll cells

Mitochondria are frequently observed in the vicinity of chloroplasts in photosynthesizing cells, and this association is considered necessary for their metabolic interactions. We previously reported that, in leaf palisade cells of Arabidopsis thaliana, mitochondria exhibit blue‐light‐dependent redistribution together with chloroplasts, which conduct accumulation and avoidance responses under the control of blue‐light receptor phototropins. In this study, precise motility analyses by fluorescent microscopy revealed that the individual mitochondria in palisade cells, labeled with green fluorescent protein, exhibit typical stop‐and‐go movement. When exposed to blue light, the velocity of moving mitochondria increased in 30 min, whereas after 4 h, the frequency of stoppage of mitochondrial movement markedly increased. Using different mutant plants, we concluded that the presence of both phototropin1 and phototropin2 is necessary for the early acceleration of mitochondrial movement. On the contrary, the late enhancement of stoppage of mitochondrial movement occurs only in the presence of phototropin2 and only when intact photosynthesis takes place. A plasma‐membrane ghost assay suggested that the stopped mitochondria are firmly adhered to chloroplasts. These results indicate that the physical interaction between mitochondria and chloroplasts is cooperatively mediated by phototropin2‐ and photosynthesis‐dependent signals. The present study might add novel regulatory mechanism for light‐dependent plant organelle interactions.     

Polymorphisms of TNFalpha, IL1beta, and IL1RN genes in chronic obstructive pulmonary disease

It is recognized that genetic factors play a role in the susceptibility to COPD. COPD is characterized by airflow limitation. Chronic inflammation causes small airway disease and parenchymal destruction, leading to the airflow limitation. Polymorphisms in pro-inflammatory cytokine genes may confer a risk for the development of COPD. A case-control association study was performed in Japanese population (88 COPD patients and 61 controls) and Egyptian population (106 patients and 72 controls). Genotype and allele frequencies of the TNFalpha -308 G/A and +489 G/A polymorphisms, the IL1beta -511 C/T, -31 T/C, and +3954 C/T polymorphisms, and a VNTR polymorphism in intron 2 of the IL1RN gene were investigated. In addition, pairwise haplotype frequencies were analyzed. When studied independently, none of the polymorphisms were associated with the development of COPD in both populations. However, in the Egyptian population, the distributions of the haplotype (IL1beta -31 T/C : IL1beta +3954 C/T) were significantly different between the COPD patients and the controls (p(corr)=0.0037). Our findings suggest that this haplotype within the IL1beta gene may be involved in the pathogenesis of COPD and that the genetic factors of COPD susceptibility might be different between different populations.     

Nod Factor/Nitrate-Induced CLE Genes that Drive HAR1-Mediated Systemic Regulation of Nodulation

Host legumes control root nodule numbers by sensing externaland internal cues. A major external cue is soil nitrate, whereasa feedback regulatory system in which earlier formed nodulessuppress further nodulation through shoot–root communicationis an important internal cue. The latter is known as autoregulationof nodulation (AUT), and is believed to consist of two long-distancesignals: a root-derived signal that is generated in infectedroots and transmitted to the shoot; and a shoot-derived signalthat systemically inhibits nodulation. In Lotus japonicus, theleucine-rich repeat receptor-like kinase, HYPERNODULATION ABERRANTROOT FORMATION 1 (HAR1), mediates AUT and nitrate inhibitionof nodulation, and is hypothesized to recognize the root-derivedsignal. Here we identify L. japonicus CLE-Root Signal 1 (LjCLE-RS1)and LjCLE-RS2 as strong candidates for the root-derived signal.A hairy root transformation study shows that overexpressingLjCLE-RS1 and -RS2 inhibits nodulation systemically and, furthermore,that the systemic suppression depends on HAR1. Moreover, LjCLE-RS2expression is strongly up-regulated in roots by nitrate addition.Based on these findings, we propose a simple model for AUT andnitrate inhibition of nodulation mediated by LjCLE-RS1, -RS2peptides and the HAR1 receptor-like kinase.     

Water Soluble Pigments Containing Xylose and Glucose in Gametangia of the Green Alga, Bryopsis maxima

Several water-soluble pigments were purified from gametangiaof Bryopsis maxima by liquid chromatography and characterizedby pyridylamination and high-performance anion-exchange chromatography.The structure of the main red pigment is proposed based on thedata of infrared spectrum, Mass spectrum, ¹H and ¹³C NMR spectraand pyridylamino analysis. As a consequence, this pigment containeda tetrapyrrole with phytol and a sugar chain comprised of xyloseand glucose. The sequence of the sugars in the chain was determinedbased on its Mass spectrum. The pigment was similar to chlorophyll-originpigments observed in other plants. No aldehyde group, however,was present at C5 in the open tetrapyrrole chain. (Received August 3, 1994; Accepted November 10, 1994)     

Gene duplications and the evolution of c-type lysozyme during adaptive radiation of East African cichlid fish

Given the reported degraded nature of DOC in the Rio Negro, and low oxygen, pH, and bacterial riverine levels, we hypothesized: (1) DOC would have strong humic and fulvic acid fluorescence signals with high aromaticity and large mean molecular weight; and (2) photo-oxidation rates would be slow, and reactive oxygen species (ROS) concentrations low, producing no oxidative stress in biota. We surveyed the environment and properties of DOC and explored DOC photo-oxidation and fish sensitivity to DOC products. DOC properties were investigated using absorption and fluorescence indices and parallel factor analysis (PARAFAC) of excitation–emission matrices. ROS concentrations were measured spectrophotometrically. A native fish, Hemigrammus levis, was exposed to photo-oxidizing DOC and its tissues (brain, gill, liver) assayed for changes in antioxidant and biotransformation enzymes. With respect to our hypotheses, (1) DOC was highly terrigenous, with high SAC₃₄₀ values (aromaticity), high capacity to produce ROS, and high tryptophan-like fluorescence (bacterial, autochthonous signal); (2) photo-oxidation rates were appreciable, while products were related to mean UV-radiation levels (total radiation was constant). ROS levels were often higher than freshwater averages, yet fish experienced no oxidative stress. Results suggest photo-oxidation influences patterns in C-cycling, bacterial production and community dynamics between wet and dry seasons.     

Structural Analysis ofArabidopsis thaliana Chromosome 5. VI. Sequence Features of the Regions of 1,367,185 bp Covered by 19 Physically Assigned P1 and TAC Clones

Nineteen Pl and TAC clones, which have been mapped on the finephysical map of the Arabidopsis thaliana chromosome 5, weresequenced according to the shotgun-based strategy, and theirstructural features were analysed. The total length of the regionssequenced in this study was 1,367,185 bp. Combining this withthe regions covered by 90 P1 and TAC clones proviously reported,the total length of chromosome 5 sequenced to date becomes 8,058,855bp. On the basis of similarity search against protein and ESTdatabases and gene modeling with computer programs, a totalof 330 potential protein-coding regions were identified, bringingan average density of the genes to approximately one gene per4.1 kb. Introns were identified in 81.0% of the potential proteingenes for which the entire gene structure was predicted, withan average number per gene of 4.2 and an average length of theintrons of 180 bp. The RNA-coding genes identified were 9 tRNAgenes corresponding to 8 amino acid species and 2 genes forU2 nuclear RNA. These sequence features are essentially identicalto those in the previously reported sequences. The sequencedata and gene information are available on the World Wide Webdatabase KAOS (Kazusa Arabidopsis data Opening Site) at http://www.kazusa.or.jp/arabi/.     

Isolation and characterization of different-sized nucleoli from Ehrlich ascites tumor cells : Evidence of different nucleolar ribosomal cistrons

A procedure was developed for isolation of variously sized nucleoli in order to study the mechanism of nucleolar formation from multiple nucleolar organizers and to compare the compositions of different-sized nucleoli from Ehrlich ascites tumor cells. Relatively small nucleoli and large nucleoli from Ehrlich ascites tumor cells were separated by centrifugation at 400 g for 5 min in a layer of 0.34 M sucrose over 0.88 M sucrose. Small nucleoli remained in the 0.34 M sucrose layer while the large nucleoli accumulated in the 0.88 M sucrose.Three fractions, provisionally named small, intermediate and large nucleoli, containing 0.33, 0.41 and 0.84 pg DNA/nucleolus, respectively, were separated. Unfractionated nucleoli contained 0.59 pg DNA/nucleolus. The RNA content also increased with the size of the nucleolus and no significant difference was observed in the RNA/DNA ratios in the three fractions. Large nucleoli incorporated more [³H]uridine and [³²P]orthophosphate into RNA than did small nucleoli, but the base compositions of the RNAs extracted from the different-sized nucleoli were similar. No significant fragmentation occurred on sonication of large nucleoli for 3 min, so the observed difference in the DNA contents was not due to mechanical damage of the nucleoli.The DNAs of these different-sized nucleoli were analysed on CsCl gradients. The nucleoli contained similar percentages of satellite DNA (20–22%) which were also similar to those of total, unfractionated nucleoli. Approx. 10% of the extranucleolar DNA is satellite DNA—thus the nucleolar fractions were probably not appreciably contaminated with extranucleolar DNA. The DNA of small nucleoli contained a slightly lower percentage (0.058%) of ribosomal cistrons than large nucleoli (0.081%). This means that the higher content of DNA in the large nucleoli is not merely due to longer sized chromatin with extra regions of the vicinity of nucleolar organizers. Thus these results suggest that the total content of ribosomal cistrons/nucleolus is roughly proportional to the DNA content of the nucleoli, at least in Ehrlich ascites tumor cells. Namely, the number of ribosomal cistrons per nucleolus for small, intermediate and large nucleoli is 40, 60 and 130, respectively.     

Linking microhabitat availability and local density of rainbow trout in low-gradient Japanese streams

Quantification of reach-based microhabitat availability for rainbow trout (Oncorhynchus mykiss), considering their microhabitat requirements in two low-gradient streams, northern Japan, was attempted to test for habitat space limitation of local trout density. Underwater observations revealed that fish selected microhabitats of moderate current velocity, relatively greater depth and shorter distance to overhead cover in both streams, although habitat features used and available differed slightly between the streams. Habitat space for fish potentially available in the channel environment was evaluated using principal component analysis (PCA) of both available and used microhabitat. A close relationship was evident in both streams between reach-based microhabitat availability and fish density, which was assessed by a three-pass removal method. Direct estimates of fish microhabitat availability using PCA can contribute to accurate predictions of local fish density and provide insight into the mechanisms responsible for fish–habitat relationships in streams.