Disrupted phylogeographical microsatellite and chloroplast DNA patterns indicate a vicariance rather than long‐distance dispersal origin for the disjunct distribution of the Chilean endemic Dioscorea biloba (Dioscoreaceae) around the Atacama Desert

Aim The Chilean endemic Dioscorea biloba (Dioscoreaceae) is a dioecious geophyte that shows a remarkable 600 km north–south disjunction in the peripheral arid area of the Atacama Desert. Its restricted present‐day distribution and probable Neogene origin indicate that its populations have a history linked to that of the Atacama Desert, making this an ideal model species with which to investigate the biogeography of the region. Location Chile, Atacama Desert and peripheral arid area. Methods Two hundred and seventy‐five individuals from nine populations were genotyped for seven nuclear microsatellite loci, and plastid trnL–F and trnT–L sequences were obtained for a representative subset of these. Analyses included the estimation of genetic diversity and population structure through clustering, Bayesian and analysis of molecular variance analyses, and statistical parsimony networks of chloroplast haplotypes. Isolation by distance was tested against alternative dispersal hypotheses. Results Microsatellite markers revealed moderate to high levels of genetic diversity within populations, with those from the southern Limarí Valley showing the highest values and northern populations showing less exclusive alleles. Bayesian analysis of microsatellite data identified three genetic groups that corresponded to geographical ranges. Chloroplast phylogeography revealed no haplotypes shared between northern and southern ranges, and little haplotype sharing between the two neighbouring southern valleys. Dispersal models suggested the presence of extinct hypothetical populations between the southern and northern ranges. Main conclusions Our results are consistent with prolonged isolation of the northern and southern groups, mediated by the life‐history traits of the species. Significant isolation was revealed at both large and moderate distances as gene flow was not evident even between neighbouring valleys. Bayesian analyses of microsatellite and chloroplast haplotype diversity identified the southern area of Limarí as the probable area of origin of the species. Our data do not support recent dispersal of D. biloba from the southern range into Antofagasta, but indicate the fragmentation of an earlier wider range, concomitant with the Pliocene–Pleistocene climatic oscillations, with subsequent extinctions of the Atacama Desert populations and the divergence of the peripheral ones as a consequence of genetic drift.     

盾叶薯蓣地上部分的三个新甾体皂甙

从盾叶薯蓣Dioscorea zingiberensis Wright地上部分分离鉴定了四个甾体皂甙,经鉴定甙A为约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)]-β-D-葡萄吡喃糖甙;甙B为24α-羟基约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)]β-D-葡萄吡喃糖甙;甙C为约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)][β-D-葡萄吡喃糖基(1→4)]-β-D-葡萄吡喃糖基;甙D为约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)][β-D-葡萄吡喃糖基(1→3)]-β-D-葡萄吡喃糖甙。前三者为新化合物,分别命名为盾叶皂甙A_1、A_2、A_3(zingiberoside A_1、A_2、A_3),其中盾叶皂甙A_2的甙元为一新甾体皂甙元,命名为盾叶皂甙元(zingiberogenin)。     

Physical map of chloroplast DNA of aerial yam,Dioscorea bulbifera L.

Summary A physical map of chloroplast DNA (ctDNA) of aerial yam, Dioscorea bulbifera L. was constructed using three restriction endonucleases, PstI, SalI, and SmaI. In addition, a clone bank of the BamHI-digested fragments were generated, and the locations of most BamHI fragments on the map were also determined. The ctDNA of D. bulbifera was found to be a circular molecule with a total size of ca. 152 kb involving two inverted repeats of ca. 25.5 kb, and small and large single copy regions of ca. 18.5 and 83.4 kb, respectively. The genes for the large subunit of the ribulose 1,5-bisphosphate carboxylase (rbcL) and the ATP-synthase subunits and (atpB/atpE) were mapped.Contribution from the Plant Germ-plasm Institute and the Laboratory of Genetics (No. 504), Faculty of Agriculture, Kyoto University, Japan. The work was supported in part by a Grant-in-Aid (No. 60400005) from the Ministry of Education, Science and Culture, Japan     

In vitro tuberization in white yam (Dioscorea rotundata Poir)

Nodal cuttings of white yam were induced to produce microtubers on a MS-revised medium supplemented with various concentrations of sucrose, 20 mgl^–1 L-cysteine, 0.5 mgl^–1 kinetin and 0.7% agar. The frequency of tuberization was affected by the daylength, which is optimal at 12 and 16 h of light depending on the sucrose concentration. The microtubers were planted in a seed bed and grown to maturity. The importance of in vitro tuberization of yam as a means of international germplasm distribution or exchange as well as for the propagation of planting material is discussed.     

Enzyme-amplified enzyme-linked immunosorbent assay for gibberellin A4 based on the NAD-dependent redox cycle

An antiserum against gibberellin A₄ (GA₄) raised in rabbits and its partially purified antibodies were used to develop radioimmunoassay (RIA) and indirect enzyme-linked immunosorbent assays (ELISAs) for GA₄. Of three immunoassays tested, an ELISA based on the NAD-dependent redox cycle (enzyme-amplified ELISA) had highest sensitivity. Levels of methylated GA₄ detected by this most sensitive method ranged from 0.1 fmol/assay (3.5 fg/assay) to 0.1 pmol/assay (3.5 pg/assay) suggesting applicability of this method to the detection of gibberellins in purified plant extracts.     

Purification and some properties of polyphenol oxidase from the yam tubers, Dioscorea bulbifera

In a comparison of the polyphenol oxidase activity of various species of yam tubers the greatest enzyme activity was found in D. bulbifera. The enzyme was purified from acetone powder extracts of this plant. Ammonium sulphate fractionation, followed by ion exchange chromatography and gel filtration gave 22-fold purification. The final product gave a single band on polyacrylamide disc gel electrophoresis. The purified enzyme showed activity towards catechol, pyrogallol and dl-β-3,4-dihydroxyphenylalanine (dl-DOPA) and had a MW 115000 ± 2000. It was characterized by response to various inhibitors. β-Mercaptoethanol, dithioerythritol, l-cysteine, sodium metabisulphite and KCN inhibited strongly.     

Life history and population dynamics of the Japanese Yam,Dioscorea japonica Thunb.

The adaptive significance of the emergence mode ofDioscorea japonica was studied with respect to initial plant size (seed, bulbil and tuber) and light intensity, using mathematical simulation based on Yokoi's (1976) model. Under 1.5% full sunlight conditions, plants emerging with only one leaf did not develop a shoot system throughout the growing period (Hori and Oshima, 1986). Simulation indicated that, for this species of plant under poor productive conditions, the optimal time for switch-over from the vegetative to reproductive growth phase to maximize the tuber weight at the end of the growing period, occurred immediately following the start of autotrophic growth. By means of shoot growth patterns, small and large size plants acquired the ability of shade tolerance and shade avoidance, respectively. Further, the life history ofD. japonica could be expressed as a flow chart based on plant size and light intensity data.     

内生Bacillus svelezensis HBB5菌株发酵盾叶薯蓣产薯蓣皂苷元的研究

目的探讨内生Bacillus svelezensis HBB5菌株发酵宿主植物盾叶薯蓣产薯蓣皂苷元的能力。方法接种内生B.svelezensis HBB5及B.subtilis ATCC 6633菌株(0.35×10~8 CFU/mL)至含盾叶薯蓣地下茎组织的液体培养基,32℃、165~185 r/min连续发酵108 h,检测发酵液细菌、pH、淀粉、麦芽糖、葡萄糖、淀粉酶(α-amylase)及薯蓣皂苷元溶出率等指标。结果内生B.svelezensis HBB5菌株有较强的酸、碱耐受力[pH(4.8±0.2)~(8.4±0.2)],相比B.subtilis ATCC 6633[pH(5.2±0.2)~(8.7±0.2)]差异不明显;前者达峰值生长量(60×10~(8±2) CFU/mL)明显高于后者(32×10~(8±2) CFU/mL)。发酵36~60 h时,B.svelezensis HBB5、B.subtilis ATCC 6633菌株发酵液的淀粉、麦芽糖、葡萄糖浓度达峰值,分别为(37.41±3.12)、(27.83±2.14)ng/mL,(21.06±1.25)、(16.54±1.08)ng/mL,(54.33±3.12)、(36.65±2.10)ng/mL,前者均高于后者。同时,B.svelezensis HBB5菌株维持高的α-amylase酶活性及薯蓣皂苷元溶出率。结论内生B.svelezensis HBB5菌株拥有较强的耐酸碱、降解淀粉、提高薯蓣皂苷元溶出的能力,为工业生产薯蓣皂苷元提供了一个新的方法。