Cyclopeptides from Sagina japonica (Caryophyllaceae)

Two new cyclic peptides, named sajaponicin C (1) and sajaponicin D (2), were isolated from the whole plants of Sagina japonica (Caryophyllaceae). Their structures were determined as cyclo(Pro(2)-Leu(2)-Tyr-Leu(1)-Phe(1)-Pro(3)-Phe(2)-Pro(1)) (1) and cyclo(Pro(1)-Pro(2)-Pro(3)-Pro(4)-Phe(1)-Gly-Thr-Ser-Phe(2)-Ile-Tyr) (2) on the basis of spectroscopic data, especially by two-dimensional (2D) NMR techniques.     

Freezing-altered palatability of Bradford pear to Japanese beetle: evidence for decompartmentalization and enzymatic degradation of feeding deterrents

The basis for resistance of Bradford callery pear, Pyrus calleryana Decaisne Bradford, [Rosaceae] to the Japanese beetle, Popillia japonica Newman, was investigated. Chloroform-dipping rendered leaves palatable, initially suggesting that deterrent waxes had been removed. However, extracts containing surface waxes were not deterrent. Subsequent experiments showed that increased palatability of solvent-dipped leaves is associated with enzymatic tissue browning, characteristic of polyphenol oxidases, rather than simply release of phagostimulants from surface disruption of damaged leaves. Frozen and thawed leaves showed similar browning, becoming increasingly palatable for several hours after thawing. Palatability changes were temperature- and aerobic-sensitive, further evidence that oxidizing enzymes are involved. Juice from leaves that had been frozen and thawed stimulated feeding on glass fiber disks, whereas fresh leaf juice did not. Survival and fecundity were much higher for beetles fed frozen and thawed or chloroform-dipped Bradford pear leaves than for beetles fed normal leaves. We hypothesize that decompartmentalization of deterrent compounds, possibly phenolics, followed by enzymatic oxidation and altered leaf chemistry may explain the increased palatability of chloroform-dipped or frozen and thawed Bradford pear tissue to P. japonica. This approach may be helpful in identifying specific compounds responsible for resistance of woody plants to generalist insects.     

Sequence analysis of the gene encoding a spotted fever group-specific intracytoplasmic protein PS120 of Rickettsia japonica

The 3,438-nucleotide (nt) sequence containing a 3,054-nt open reading frame of the gene (rps120) encoding an antigenic, intracytoplasmic, spotted fever group-specific and heat-stable 120-kilodalton protein (PS120) of Rickettsia japonica was determined. The nt and deduced 1,018 amino-acid (aa) sequences were compared to those of R. conorii since only those of this species had been determined among SFG rickettsiae. The homologies of these sequences between R. japonica and R. conorii were considerably high at 97 and 95%, respectively. These high homologies were comparable to those of beta-peptides encoded by the ompB genes among SFG rickettsiae. It was also found that the genome of R. prowazekii contained a nt sequence with 68% homology to that of the rps120 gene of R. japonica.     

Chemical and physical defence in early and late leaves in three heterophyllous birch species native to northern Japan

BACKGROUND AND AIMS: Betula ermanii, B. maximowicziana and B. platyphylla var. japonica have heterophyllous leaves (i.e. early leaves and late leaves) and are typical pioneer species in northern Japan. Chemical and physical defences against herbivores in early and late leaves of these species were studied. METHODS: Two-year-old seedlings were grown under full sunlight in a single growing season. Three-week-old leaves of each seedling were harvested three times (May, July and October). Total phenolics and condensed tannin content were determined for chemical defence and leaf toughness and trichome density were assessed for physical defence. Defoliation of early leaves in May was also performed to study the contribution of early leaves to subsequent growth. KEY RESULTS: Chemical and physical defences were greater in early than late leaves in B. platyphylla and B. ermanii, whereas the reverse was true in B. maximowicziana. In contrast to its weak chemical defences, the trichome density in B. maximowicziana was very high. In B. platyphylla and B. ermanii, the relative growth rates (RGR) were greater early in the growing season. Negative effects on growth of removal of early leaves were significant only in B. platyphylla. CONCLUSIONS: B. platyphylla and B. ermanii invest in defence in early rather than late leaves, since early leaves are crucial to subsequent growth. In contrast, B. maximowicziana more strongly defends its late leaves, since its RGR is maintained at the same level throughout the growing season.     

Genetic diversity and its implications in the conservation of endangered<Emphasis Type="Italic">Zostera japonica</Emphasis> in Korea

As part of the on-going effort to conserve endangeredZostera japonica Ascher. & Graebn. in Korea, we have used RAPD band patterns to analyze its genetic structure and diversity. Out of 50 primers tested, 45 formed amplified bands with its genome, including 814 polymorphic and 28 monomorphic bands. The highest number (120) was found in the population of Geoje-do; the smallest (58), in Anmyeon-do. An examination of its genetic structure with AMOVA revealed that about 50% of all variations could equally be assigned to within and between populations. The statistical value G_st (index of genetic differences) was 0.49, and the average number of individuals exchanged between populations per generation (N _e m) was calculated as 0.26. Although the habitats ofZ. japonica in Korea are disappearing at an alarming rate, significant levels of genetic variation still exist, especially in the Geoje-do population. Therefore, any recovery strategy for this endangered species should be planned on the basis of this genetic diversity among populations.     

Variation in DNA-ploidy Levels of Reynoutria Taxa in the Czech Republic

The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. japonica, R. japonica var. compacta, R. sachalinensis and R. xbohemica. By using flow cytometry, cytological variability within the genus is described based on 257 Reynoutria samples. The varieties of R. japonica are cytologically uniform, var. japonica is exclusively octoploid (2n = 8x = 88) and var. compacta occurs only as a tetraploid (2n = 4x = 44), but R. sachalinensis and R. xbohemica exhibit some variation in chromosome numbers. Reynoutria sachalinensis is predominantly tetraploid (2n = 4 x = 44), but also occurs occasionally as hexaploid and octoploid cytotypes. The most common ploidy level in R. xbohemica is hexaploid (2n = 6x = 66), but tetraploid and octoploid clones were also found. The four taxa occurring in the Czech Republic are described briefly and the possible origins of the cytotypes discussed.     

Genetic structure of age classes in Camellia japonica (Theaceae)

Camellia japonica L. (Theaceae), an insect- and bird-pollinated, broad-leaved evergreen tree, is widely distributed in Japan and the southern Korean peninsula. The species has a relatively even age distribution within populations, which may influence the spatial genetic structure of different age classes relative to species with typical L-shaped age distributions. To determine whether the internal spatial genetic structure found in seedlings and young individuals carries over into adults, we used allozyme loci, F-statistics, spatial autocorrelation statistics (Moran's I), and coancestry measures to examine changes in genetic structure among seven age classes in a population (60-m x 100-m area) in southern Korea. In seedlings, weak but significant positive values of Moran's I-statistics and coancestry measures were found for distances less than 14 m, which is consistent with a mechanism of limited seed dispersal combined with overlapping seed shadows. This spatial structure, however, dissipates in older age classes, and in adults genetic variation has an essentially random spatial distribution. Morisita's index of dispersion of individuals in each age class showed that seedlings and juveniles are more highly clustered than are older individuals. These results suggest that self-thinning changes the spatial relationships of individuals, and thus genotypes. A multilocus estimate of FST (0.008) shows a small but statistically significant difference in allele frequencies among age classes. In summary, intrapopulation genetic structure within and among age classes of C. japonica was significant but weak. Despite presumably limited seed dispersal, weak spatial genetic structure in juveniles suggests overlapping seed shadows followed by self-thinning during recruitment. The present study also demonstrates that studies of spatial genetic structure focusing on limited numbers of generations may not be sufficient to reveal the entire picture of genetic structure in populations with overlapping generations.     

Two types of HKT transporters with different properties of Na+ and K+ transport in Oryza sativa

It is thought that Na+ and K+ homeostasis is crucial for salt-tolerance in plants. To better understand the Na+ and K+ homeostasis in important crop rice (Oryza sativa L.), a cDNA homologous to the wheat HKT1 encoding K+-Na+ symporter was isolated from japonica rice, cv Nipponbare (Ni-OsHKT1). We also isolated two cDNAs homologous to Ni-OsHKT1 from salt-tolerant indica rice, cv Pokkali (Po-OsHKT1, Po-OsHKT2). The predicted amino acid sequence of Ni-OsHKT1 shares 100% identity with Po-OsHKT1 and 91% identity with Po-OsHKT2, and they are 66-67% identical to wheat HKT1. Low-K+ conditions (less than 3 mM) induced the expression of all three OsHKT genes in roots, but mRNA accumulation was inhibited by the presence of 30 mM Na+. We further characterized the ion-transport properties of OsHKT1 and OsHKT2 using an expression system in the heterologous cells, yeast and Xenopus oocytes. OsHKT2 was capable of completely rescuing a K+-uptake deficiency mutation in yeast, whereas OsHKT1 was not under K+-limiting conditions. When OsHKTs were expressed in Na+-sensitive yeast, OsHKT1 rendered the cells more Na+-sensitive than did OsHKT2 in high NaCl conditions. The electrophysiological experiments for OsHKT1 expressed in Xenopus oocytes revealed that external Na+, but not K+, shifted the reversal potential toward depolarization. In contrast, for OsHKT2 either Na+ or K+ in the external solution shifted the reversal potential toward depolarization under the mixed Na+ and K+ containing solutions. These results suggest that two isoforms of HKT transporters, a Na+ transporter (OsHKT1) and a Na+- and K+-coupled transporter (OsHKT2), may act harmoniously in the salt tolerant indica rice.     

Pseudodactylogyrus kamegaii sp. n. (Monogenea: Pseudodactylogyridae) from wild Japanese eel,Anguilla japonica

The monogenean Pseudodactylogyrus kamegaii sp. n. is described, based on specimens collected from the gills of wild Japanese eel Anguilla japonica caught in Chiba Prefecture, Japan. This species is the most similar to P. anguillae (Yin and Sproston, 1948), but different in the shape and measurements of the male copulatory organ, vagina and marginal hook. This new species was collected from the eel in brackish waters, while P. anguillae and P. bini, the other known pseudodactylogyrids of Japanese eel, have been recorded only in fresh waters.     

中华绒螯蟹卵巢RACE Cdna文库的构建

应用抑制性差减杂交技术 ,已经获得了中华绒螯蟹卵巢发育过程中差异表达基因的部分cDNA序列。为了进一步获得基因的全长cDNA序列 ,运用SMART技术 ,成功构建了中华绒螯蟹卵巢 (Ⅲ期 )RACEcDNA文库。琼脂糖凝胶电泳结果表明 ,文库所含全长cDNA的长度主要集中在 5 0 0～ 2 0 0 0bp之间 ,RACEPCR结果表明 ,所用基因特异性引物与接头引物皆能扩增出产物 ,说明所构文库的质量较好 ,适于用RACE方法从中分离中华绒螯蟹卵巢发育相关基因的全长cDNA。