Homo-Phytochelatins Are Synthesized in Response to Cadmium in Azuki Beans

In a recent report, it was claimed that azuki beans (Vigna angularis) do not synthesize phytochelatins (PCs) upon exposure to cadmium, although glutathione (GSH), the substrate for PC synthesis, is present in this plant. This legume species thus would be the first exception in the plant kingdom that would fail to complex heavy metals by PCs. Here, we report that not GSH, but only homoglutathione can be detected in this plant and that homo-phytochelatins are formed when azuki beans are challenged with heavy metals such as cadmium. We also show that the 5,5'-dithiobis(2-nitrobenzoic acid)-oxidized GSH reductase recycling assay, used for GSH quantification in the recent study of heavy metal tolerance in azuki beans, reacts both with GSH and homoglutathione and therefore cannot be used when biological samples should be analyzed exclusively for GSH.     

The Linamarin beta-Glucosidase in Costa Rican Wild Lima Beans (Phaseolus lunatus L.) Is Apoplastic

Analysis of mesophyll protoplasts and cell wall extracts of leaf discs of Costa Rican wild lima bean (Phaseolus lunatus L.) shows that the linamarase activity is confined to the apoplast. Its substrate linamarin, together with the related enzyme hydroxynitrile lyase, is found inside the cells. This compartmentation prevents cyanogenesis from occurring in intact tissue, and suggests that linamarin has to be protected during any translocation across the linamarase rich apoplast.     

Chemical Composition of Ceramide and Cerebroside in Azuki Bean Seeds

The enzymic properties of three electrophoretically distinct β-glucosidases, β-glucosidase-1, -2 and -3, from Aspergillus aculeatus No. F-50 were investigated. β-Glucosidase-3 had a low optimum pH of 3.0, but the other two enzymes had optimum pHs of 4.0~4.5. Both β-glucosidase-1 and -2 were potently active not only on soluble cellooligosaccharides, such as cellotriose to cellohexaose, but also on insoluble cellooligosaccharide, of which the average degree of polymerization was 20. On the contrary, β-glucosidase-3 was only slightly active on the insoluble substrate. The combined use of either β-glucosidase-1 or -2 and endo-glucanase remarkably stimulated the hydrolysis of amorphous cellulose, yielding glucose only. But β-glucosidase-3 did not show such a synergistic effect, and the glucose content of the hydrolyzate was only about 60%.     

Bone and Joint Disorders in Wild Japanese Macaques from Nagano Prefecture,Japan

I studied bone and joint disorders in wild Japanese macaques (Macaca fuscata fuscata) in order to discern some aspects of their life history from the skeletal material. The specimens comprise 107 nearly complete skeletons of subadults and adults that were killed as crop-raiding monkeys between 1997 and 1998 in Nagano Prefecture, Japan. The most frequent disorder is angular deformity due to fractures: 80 healed fractures in 31 of 52 males and 71 healed fractures in 26 of 55 females. Secondary osteoarthritis due to fractures is rare. Two males have osteochondritis dissecans bilaterally on the posterior surface of the lateral femoral condyles. Degenerative changes are common in the aged individuals. Fractures of the trunk—clavicle, scapula, vertebrae, ribs or hip—are frequent in the males. Contrarily, the majority of fractures in females are in the hands and feet. While most fractures in males appear to have occurred during adulthood, those in females occurred during childhood and senescence. Interindividual violence should not be regarded as a principal cause for fractures in males and females because there is no bite wound except perhaps for one case of an amputated digit. Fractures of the trunk in males were probably caused by impact forces against their shoulders or hips or both caused by rolling down a steep slope or falling out of trees, perhaps during intertroop transfers.     

Wild boars: A potential source of Erysipelothrix rhusiopathiae infection in Japan

The potential role of wild boars as a source of erysipelas infection was investigated. An ELISA test of wild boar serum samples from 41 prefectures in Japan revealed that proportions of the Erysipelothrix rhusiopathiae‐positive samples were very high in all the prefectures, and the mean positive rate was 95.6% (1312/1372). Serovars of E. rhusiopathiae isolates from wild boars were similar to those of previously reported swine isolates, and all serovar isolates tested were found to be pathogenic to mice. These results suggest that wild boars in Japan constitute a reservoir of E. rhusiopathiae and may pose risks to other animals.     

Azuki bean cells are hypersensitive to cadmium and do not synthesize phytochelatins

Suspension-cultured cells of azuki bean (Vigna angularis) as well as the original root tissues were hypersensitive to Cd (<10 microM). Repeated subculturings with a sublethal level of Cd (1-10 microM) did not affect the subsequent response of cells to inhibitory levels of Cd (10-100 microM). The azuki bean cells challenged to Cd did not contain phytochelatin (PC) peptides, unlike tomato (Lycopersicon esculentum) cells that have a substantial tolerance to Cd (>100 microM). Both of the cell suspensions contained a similar level of reduced glutathione (GSH) when grown in the absence of Cd. Externally applied GSH to azuki bean cells recovered neither Cd tolerance nor PC synthesis of the cells. Furthermore, enzyme assays in vitro revealed that the protein extracts of azuki bean cells had no activity converting GSH to PCs, unlike tomato. These results suggest that azuki bean cells are lacking in the PC synthase activity per se, hence being Cd hypersensitive. We concluded that the PC synthase has an important role in Cd tolerance of suspension-cultured cells.     

Prevalence of Antibodies to Borrelia Spirochetes among Wild Small Rodents in Central and Western Japan

Field rodents serve as a reservoir for Lyme disease spirochetes. To evaluate the antibody responses of rodents against different Borrelia species in relation to fauna of vector ticks feeding on them, we examined 272 sera of wild rodents, Apodemus speciosus, A. argenteus, and Eothenomys smithii, obtained in 27 locations in central and western Japan from 1981 to 1994. As to prevalences by rodent species using immunoperoxidase test, A. speciosus, A. argenteus and E. smithii showed 29.4%, 11.6% and 30.8% reactivity to Borrelia japonica, 10.7%, 7.2% and 3.8% to B. afzelii, 0.6%, 1.4% and 0% to B. garinii, and 14.7%, 7.2% and 11.5% to an unknown Borrelia species designated as It type, respectively. Each antibody to B. japonica, B. afzelii and B. sp. It type was detected widely both in central and western Japan, but the antibody to B. garinii was scarcely detectable in any area and rodent species examined. Apodemus mice in high mountain altitudes tend to have antibody to B. afzelii or B. japonica, and those in lower altitudes tend to have B. japonica or B. sp. It type. All 13 Apodemus mice from which B. japonica or B. sp. It type were isolated showed higher titers of antibodies to each homologous Borrelia species. The present results indicate that these antibody prevalences among rodents may be associated with dominant Ixodes ovatus and sporadic I. persulcatus on the mainland of Japan, and that Apodemus mice may not be an efficient reservoir for B. garinii. Such a serosurvey is a useful measure to evaluate the natural distribution of the pathogen.     

Isoenzyme Variation in Asian Beans

Electrophoretic variation of isoenzyme characters encoded by 20 gene loci has been studied in 9 species of Asian beans, comprising subgenus Ceratotropis of the genus Vigna. Four species of hypogeal germination type, V. angularis, V. umbellata, V. dalzelliana and V. minima, are shown to form a distinct monophyletic group in the subgenus, sharing common electromorphs of two major isoenzymes of aspartate aminotransferase. V. glabrescens is confirmed to be an allotetraploid derivate of two diploids closely related to V. radiata and V. umbellata, but divergent from their contemporary accessions analyzed. V. trilobata is the most variable species of the subgenus in isoenzyme characters. It reveals intraspecific differentiation at several isoenzyme loci correlated with the seed morphology and geographical localization.     

Weed and Crop Allelopathy

Allelopathy can be defined as an important mechanism of plant interference mediated by the addition of plant-produced secondary products to the soil rhizosphere. Allelochemicals are present in all types of plants and tissues and are released into the soil rhizosphere by a variety of mechanisms, including decomposition of residues, volatilization, and root exudation. Allelochemical structures and modes of action are diverse and may offer potential for the development of future herbicides. We have focused our review on a variety of weed and crop species that establish some form of potent allelopathic interference, either with other crops or weeds, in agricultural settings, in the managed landscape, or in naturalized settings. Recent research suggests that allelopathic properties can render one species more invasive to native species and thus potentially detrimental to both agricultural and naturalized settings. In contrast, allelopathic crops offer strong potential for the development of cultivars that are more highly weed suppressive in managed settings. Both environmental and genotypic effects impact allelochemical production and release over time. A new challenge that exists for future plant scientists is to generate additional information on allelochemical mechanisms of release, selectivity and persistence, mode of action, and genetic regulation. In this manner, we can further protect plant biodiversity and enhance weed management strategies in a variety of ecosystems. Referee: Dr. Steve Weller, Purdue University, Dept. of Horticulture, West Lafayette, IN 47907     

Effects of a brassinosteroid on growth and electrogenic proton extrusion in Azuki bean epicotyls

Brassinolide, a plant hormone newly isolated from pollen, promotes growth of the stem of a number of plant species. Similar effects are induced by a brassinosteroid (BR), the synthetic 24-epibrassinolide. In this paper the effects of BR on acid secretion and transmembrane electrical potential difference in Azuki bean ( Vigna angularis , Ohwi and Ohashi cv. Takara) epicotyls were determined in short term experiments and compared with the effects on growth. At concentrations between 10^-7 to 10^-5 M , BR stimulates, similarly to indole-3-acetic acid (IAA), growth and H⁺ extrusion and hyperpolarizes the transmembrane electric potential (PD). These effects of BR, as well as those of IAA, are suppressed by inhibitors of RNA and protein synthesis. All these effects of BR and IAA appear roughly additive, even when both hormones are present at their optimal concentrations. The data are interpreted as showing that the action of BR on growth is at least in part mediated by its capability to activate electrogenic proton extrusion. The additivity of the effects of BR and IAA suggests that the primary mechanism of action of the two hormones is different.     

The Sucrose-synthesizing Enzyme in the Beans

The properties of UDPG → fructose transglucosylase, partially purified from immature soybeans or broad beans, were investigated. Magnesium ions had a stimulating effect on this enzyme. Evidence was presented to show that UDPG, the glucosyl group donor for sucrose synthesis, was regenerated from UDP and G-1-P in the presence of ATP.     

Effect of Auxin on Autolysis of Cell Walls in Azuki Bean Epicotyls

Native cell walls of azuki bean epicotyls incubated in bufferautolytically released neutral sugars, abundant in galactose,and uronic acids. Treatment with 10^–5 M IAA of subapicalor basal epicotyl segments for 3 h did not influence the amountof total neutral sugars released from the cell walls duringautolysis. However, the amount of glucose and xylose releasedfrom subapical cell walls was increased by IAA. Pretreatmentwith IAA of subapical epicotyl segments enhanced the solubilizationof neutral sugars from pectinase-treated cell walls during incubationin buffer at pH 5 to 6. The amount of fucose, xylose, and glucosereleased was specifically increased by IAA. Of the sugar fractionsreleased from pectinase-treated cell walls during autolysisand subsequently separated by gel filtration on a ToyopearlHW-40S column, IAA promoted the release of oligosaccharides,consisting mainly of glucose and xylose. These results suggestthat autolytic degradation of xyloglucans is closely relatedto IAA-induced growth of azuki bean epicotyls. (Received May 19, 1989; Accepted January 5, 1990)     

杂草生态学和生物学研究进展

杂草生态学和生物学研究进展薛光（江苏省在科院植物保护研究所南京２１００１４）ＲｅｓｅａｒｃｈＰｒｏｇｒｅｓｓｅｓｉｎＷｅｅｄＥｃｏｌｏｇｙａｎｄＢｉｏｌｏｇｙ￥,ＸｕｅＧｕａｎｇ（ＰｌａｎｔＰｒｏｔｅｃｔｉｏｎＩｎｓｔｉｕｔｅ,ＪｉａｎｇｓｕＡｃａｄ...     

Inhibition of the Breakdown of Xyloglucans in Azuki Bean Epicotyls by Concanavalin A

Indole-3-acetic acid at 10 µM caused a 30% decrease inthe weight-average molecular mass of xyloglucans extracted with24% KOH from the cell walls of epicotyl segments of azuki bean(Vigna angularis Ohwi et Ohashi cv. Takara). Concanavalin A(Con A) at 2 g liter^–1 completely inhibited the IAA-inducedchange in the molecular mass of the xyloglucans. Con A alsosuppressed the autolysis of pectin-depleted cell walls, as wellas the breakdown of xyloglucans by a protein fraction that hadbeen extracted with 1 M NaCl from the cell walls of azuki beanepicotyls. These results indicate that Con A is a potent inhibitorof the breakdown of xyloglucans both in vivo and in vitro. Mostof the activity responsible for the decrease in staining byiodine and the increase in reducing power of solution of xyloglucansin the protein fraction from cell walls bound to a column ofCon A-Sepharose and was eluted by the specific hapten, methyl