Studies on Phyto-peroxidase

In a continuation of the structural studies on Japanese-radish peroxidase a. the products resulting from the action of pepsin on performic acid-oxidized apo-peroxidase a have been examined by ion-exchange chromatography on a Dowex 50W-X2 column, followed by gelfiltration chromatography on a Sephadex G-25 column and by high voltage paper electrophoresis. Seven peptides have been isolated in purified forms in yields of 6 to 39 per cent, and their amino acid compositions have been determined.     

Species diversity and primary productivity inMiscanthus sinensis grasslands

In an old field grassland dominated byMiscanthus sinensis Anderss. the community structures, phytomass, dominance ofM. sinensis and species diversity were measured. Species and life form composition of the stand were characterized by higher percentages of therophytes, woody and shrubby species, liana and alien species. From May so September in 1982, all the aboveground parts were harvested from each of the four quadrats (2 m×2 m) once a month. Seasonal peak of aboveground phytomass, in September, was 1027 g d.w.m⁻² to whichM. sinensis contributed as much as 96.5%. With the progress of the growing season,M. sinensis became increasingly important both in stand phytomass and in dominance, whereas species diversity based on the dry weight contributions of constituent species decreased. Our analysis of these seasonal trends showed that the diversity was largely a function of dominance of the most important species, rather than that of stand phytomass or productivity. The simultaneous measurements of 20 quadrats in late August 1983, also supported the above conclusion.     

Genetic structure of East Asian cultivated pears (Pyrus spp.) and their reclassification in accordance with the nomenclature of cultivated plants

By use of Bayesian statistical inference and allelic data for 18 microsatellite loci, we analyzed the genetic structure of Chinese, Korean, and Japanese pear cultivars and of native populations of Pyrus ussuriensis. Although Japanese pear cultivars had a simple genetic structure, Chinese and Korean pear cultivars were admixures of Japanese pear and native P. ussuriensis from the Asian continent. Genetic differentiation between groups of native populations and those of cultivars was high, but cultivars were not well differentiated from each other. Chinese and Korean cultivars, which have traditionally been classified as either P. ussuriensis, P. bretschneideri, or P. pyrifolia, were much closer to Japanese cultivars, which have traditionally been classified as P. pyrifolia, than to native P. ussuriensis. We propose a new classification of cultivars by using the Group concept in accordance with the International Nomenclature for Cultivated Plants, namely, the Pyrus Ussurian pear group, the Pyrus Chinese white pear group, the Pyrus Chinese sand pear group, and the Pyrus Japanese pear group.     

Visualization of the terminal structure of rice chromosomes 6 and 12 with multicolor FISH to chromosomes and extended DNA fibers

High-resolution fluorescence in situ hybridization (FISH) on interphase and pachytene nuclei, and extended DNA fibers enabled microscopic distinction of DNA sequences less than a few thousands of base pairs apart. We applied this technique to reveal the molecular organization of telomere ends in japonica rice (Oryza sativa ssp. japonica), which consist of the Arabidopsis type TTTAGGG heptameric repeats and the rice specific subtelomeric tandem repeat sequence A (TrsA). Southern hybridizations of DNA digested with Bal31 and EcoRI, and FISH on chromosomes and extended DNA fibers demonstrated that (1) all chromosome ends possess the telomere tandem repeat measuring 3–4 kb; (2) the subtelomeric TrsA occurs only at the ends of the long arms of chromosomes 6 and 12, and measure 6 and 10 kb, which corresponds to 231 and 682 copies for these sites, respectively; (3) the telomere and TrsA repeats are separated by at most a few thousands of intervening nucleotide sequences. The molecular organization for a general telomere organization in plant chromosomes is discussed.     

Fanconi anemia protein FANCD2 promotes immunoglobulin gene conversion and DNA repair through a mechanism related to homologous recombination

Recent studies show overlap between Fanconi anemia (FA) proteins and those involved in DNA repair mediated by homologous recombination (HR). However, the mechanism by which FA proteins affect HR is unclear. FA proteins (FancA/C/E/F/G/L) form a multiprotein complex, which is responsible for DNA damage-induced FancD2 monoubiquitination, a key event for cellular resistance to DNA damage. Here, we show that FANCD2-disrupted DT40 chicken B-cell line is defective in HR-mediated DNA double-strand break (DSB) repair, as well as gene conversion at the immunoglobulin light-chain locus, an event also mediated by HR. Gene conversions occurring in mutant cells were associated with decreased nontemplated mutations. In contrast to these defects, we also found increased spontaneous sister chromatid exchange (SCE) and intact Rad51 foci formation after DNA damage. Thus, we propose that FancD2 promotes a subpathway of HR that normally mediates gene conversion by a mechanism that avoids crossing over and hence SCEs.     

Which practices co‐deliver food security,climate change mitigation and adaptation,and combat land degradation and desertification?

There is a clear need for transformative change in the land management and food production sectors to address the global land challenges of climate change mitigation, climate change adaptation, combatting land degradation and desertification, and delivering food security (referred to hereafter as “land challenges”). We assess the potential for 40 practices to address these land challenges and find that: Nine options deliver medium to large benefits for all four land challenges. A further two options have no global estimates for adaptation, but have medium to large benefits for all other land challenges. Five options have large mitigation potential (>3 Gt CO₂eq/year) without adverse impacts on the other land challenges. Five options have moderate mitigation potential, with no adverse impacts on the other land challenges. Sixteen practices have large adaptation potential (>25 million people benefit), without adverse side effects on other land challenges. Most practices can be applied without competing for available land. However, seven options could result in competition for land. A large number of practices do not require dedicated land, including several land management options, all value chain options, and all risk management options. Four options could greatly increase competition for land if applied at a large scale, though the impact is scale and context specific, highlighting the need for safeguards to ensure that expansion of land for mitigation does not impact natural systems and food security. A number of practices, such as increased food productivity, dietary change and reduced food loss and waste, can reduce demand for land conversion, thereby potentially freeing‐up land and creating opportunities for enhanced implementation of other practices, making them important components of portfolios of practices to address the combined land challenges.     

Host cell protein LAMP‐2 is the receptor for Trypanosoma cruzi surface molecule gp82 that mediates invasion

Host cell invasion by Trypanosoma cruzi metacyclic trypomastigote (MT) is mediated by MT‐specific surface molecule gp82, which binds to a still unidentified receptor, inducing lysosome spreading and exocytosis required for the parasitophorous vacuole formation. We examined the involvement of the major lysosome membrane‐associated LAMP proteins in MT invasion. First, human epithelial HeLa cells were incubated with MT in the presence of antibody to LAMP‐1 or LAMP‐2. Antibody to LAMP‐2, but not to LAMP‐1, significantly reduced MT invasion. Next, HeLa cells depleted in LAMP‐1 or LAMP‐2 were generated. Cells deficient in LAMP‐2, but not in LAMP‐1, were significantly more resistant to MT invasion than wild‐type controls. The possibility that LAMP‐2 might be the receptor for gp82 was examined by co‐immunoprecipitation assays. Protein A/G magnetic beads cross‐linked with antibody directed to LAMP‐1 or LAMP‐2 were incubated with HeLa cell and MT detergent extracts. Gp82 bound to LAMP‐2 but not to LAMP‐1. Binding of the recombinant gp82 protein to wild‐type and LAMP‐1‐deficient cells, which was dose dependent and saturable, had a similar profile and was much higher as compared with LAMP‐2‐depleted cells. These data indicate that MT invasion is accomplished through recognition of gp82 by its receptor LAMP‐2.     

Type XXVI collagen,a new member of the collagen family,is specifically expressed in the testis and ovary

HSP47 is a collagen-specific molecular chaperone that specifically recognizes and binds to the triple helical domain of various types of collagens. Here we report the cloning of the entire coding region of a novel collagen-like protein by yeast two-hybrid screening of a 17.5-day whole mouse embryo cDNA library using HSP47 as a bait. The cDNA of this protein and its deduced amino acid sequence are 2,690 bp and 438 amino acids long, respectively. The protein contains two clusters of Gly-X-Y collagenous repeats and three noncollagenous domains. Northern blot analysis showed that its mRNA is specifically expressed in the testis and ovary in adult tissues and that expression in these tissues is highest in the neonate. Biochemical characterization of this protein revealed that its proline residues are hydroxylated, it undergoes N-linked glycosylation, it forms trimers, and it is secreted in vitro. Immunohistochemical studies showed that the myoid cells and the pre-theca cells synthesized it in the testis and ovary, respectively, resulting in the accumulation of this protein in the extracellular spaces of these organs. These observations suggest that this protein is a new member of the collagen protein family. We thus designated this protein as type XXVI collagen.     

Molecular cloning and characterization of Trypanosoma vivax alternative oxidase (AOX) gene, a target of the trypanocide ascofuranone

Trypanosoma vivax causes nagana disease in cattle. Since T. vivax is transmitted not only by tsetse flies but also by other biting flies (non-cyclic transmission), the parasite has been distributed to and has had a significant economic impact on wide geographical areas, including Africa and South America. Our previous study on Trypanosoma brucei brucei showed that the trypanosome alternative oxidase (TAO, TbAOX) is a promising target of chemotherapy. For this reason, we also have cloned the T vivax AOX (TvAOX) gene and characterized the recombinant enzyme. The deduced amino acid sequence (328 a.a.) of TvAOX shares 76% identity with TbAOX and contains the diiron-coordination motifs (-E-, -EXXH-) that are conserved among AOXs. The Km of recombinant TvAOX (rTvAOX) expressed in Escherichia coli for ubiquinol (87.0 +/- 0.54 microM) was significantly lower than the value for recombinant TbAOX (rTbAOX) (714 +/- 4.5 microM). Ascofuranone, the most potent inhibitor of TbAOX, was a competitive inhibitor of rTvAOX with a Ki value (0.40 +/- 0.00 nM) significantly lower than that for rTbAOX (1.29 +/- 0.00 nM). The non-cyclic transmission ability of T. vivax and the in vivo chemotherapeutic efficacy of ascofuranone against T. vivax and T. b. brucei infection are discussed in terms of these Km and Ki values.