Rapid solubilization of insoluble phosphate by a novel environmental stress-tolerant Burkholderia vietnamiensis M6 isolated from ginseng rhizospheric soil

We isolated and characterized novel insoluble phosphate (P)-solubilizing bacteria tolerant to environmental factors like high salt, low and high pHs, and low temperature. A bacterium M6 was isolated from a ginseng rhizospheric soil and confirmed to belong to Burkholderia vietnamiensis by BIOLOG system and 16S rRNA gene analysis. The optimal cultural conditions for the solubilization of P were 2.5% (w/v) glucose, 0.015% (w/v) urea, and 0.4% (w/v) MgCl₂·6H₂O along with initial pH 7.0 at 35°C. High-performance liquid chromatography analysis showed that B. vietnamiensis M6 produced gluconic and 2-ketogluconic acids. During the culture, the pH was reduced with increase in gluconic acid concentration and was inversely correlated with P solubilization. Insoluble P solubilization in the optimal medium was about 902 mg l⁻¹, which was approximately 1.6-fold higher than the yield in NBRIP medium (580 mg l⁻¹). B. vietnamiensis M6 showed resistance against different environmental stresses like 10–45°C, 1–5% (w/v) salt, and 2–11 pH range. The maximal concentration of soluble P produced by B. vietnamiensis M6 from Ca₃(PO₄)₂, CaHPO₄, and hydroxyapatite was 1,039, 2,132, and 1,754 mg l⁻¹, respectively. However, the strain M6 produced soluble P with 20 mg l⁻¹ from FePO₄ after 2 days and 100 mg l⁻¹ from AlPO₄ after 6 days, respectively. Our results indicate that B. vietnamiensis M6 could be a potential candidate for the development of biofertilizer applicable to environmentally stressed soil.     

Phylogeny of Weigela and Diervilla (Caprifoliaceae) Based on Nuclear rDNA ITS Sequences: Biogeographic and Taxonomic Implications

Weigela and three species of Diervilla were inferred from nucleotide sequence variation in the internal transcribed spacer (ITS) regions of 18-26S nuclear ribosomal DNA. Phylogenetic trees were obtained using parsimony, distance, and maximum likelihood methods. The ITS phylogenies did not support the monophyly of Weigela, which comprises three major clades. The first clade includes a single species, W. middendorffiana, which is more closely related with American genus, Diervilla. The second clade consisted of a single species, W. maximowiczii, but its relationship to other Weigela species is equivocal. The third one is a strongly supported core clade which contains the remaining Weigela species. Within the core group, W. hortensis exhibits the most distinct ITS sequence type. The hybrid origin of the species from the putative parents, W. florida and W. subsessilis, is not supported. The ITS sequence evidence favors the taxonomic hypothesis proposed by Nakai who recognized four distinct evolutionary lines (Diervilla, Macrodiervilla, Weigelastrum and Weigela). However, recognition of the two sections, Calysphyrum and Weigela was not supported in the ITS phylogenies. Substantial morphological differences between Diervilla and Weigela middendorffiana do not support the morphological stasis concept which has been considered as a general evolutionary mode among the Asian and North American disjunct taxa. Received 27 July 1998/ Accepted in revised form 7 July 1999     

Structural roles of cysteine 50 and cysteine 230 residues in Arabidopsis thaliana S-adenosylmethionine decarboxylase

The Arabidopsis thaliana S-Adenosylmethionine decarboxylase (AdoMetDC) cDNA (GenBank U63633) was cloned. Site-specific mutagenesis was performed to introduce mutations at the conserved cysteine Cys(50), Cys(83), and Cys(230), and lys(81) residues. In accordance with the human AdoMetDC, the C50A and C230A mutagenesis had minimal effect on catalytic activity, which was further supported by DTNB-mediated inactivation and reactivation. However, unlike the human AdoMetDC, the Cys(50) and Cys(230) mutants were much more thermally unstable than the wild type and other mutant AdoMetDC, suggesting the structural significance of cysteines. Furthermore, according to a circular dichroism spectrum analysis, the Cys(50) and Cys(230) mutants show a higher a-helix content and lower coiled-coil content when compared to that of wild type and the other mutant AdoMetDC. Also, the three-dimensional structure of Arabidopsis thaliana AdoMetDC could further support all of the data presented here. Summarily, we suggest that the Cys(50) and Cys(230) residues are structurally important.     

Population genomics study for the conservation management of the endangered shrub Abeliophyllum distichum

Natural monuments are IUCN Category III protected areas that play an important role in biodiversity conservation as they provide species refuge and allow species migration. Despite their status, natural monuments are often confined to cultural and fragmented landscapes due to anthropogenic land-use demands. In this population genomic study, we surveyed 11 populations of the endemic shrub Abeliophyllum distichum Nakai (Oleaceae), including five natural monument habitats, covering its range-wide distribution in South Korea. Using 2,254 SNPs as markers, our results showed a mean expected heterozygosity (He) of 0.319, with populations in the central distribution showing significantly higher He than those at the periphery. There was no significant heterozygote deficiency and inbreeding among studied populations overall (F_{IS =} ?0.098), except for a single natural monument population (GS-NM147). Population structure and differentiation was moderate to high (F_ST?=?0.196), while recent gene flow between populations appeared weak, which can be attributed to the fragmented distribution and the outcrossing mating system of the heterostylous plant. Based on these findings, we provide suggestions for the population conservation and management of this endangered species.

     

First molecular phylogenetic insights into the evolution of Eriocaulon (Eriocaulaceae,Poales)

Eriocaulon is a genus of c. 470 aquatic and wetland species of the monocot plant family Eriocaulaceae. It is widely distributed in Africa, Asia and America, with centres of species richness in the tropics. Most species of Eriocaulon grow in wetlands although some inhabit shallow rivers and streams with an apparent adaptive morphology of elongated submerged stems. In a previous molecular phylogenetic hypothesis, Eriocaulon was recovered as sister of the African endemic genus Mesanthemum. Several regional infrageneric classifications have been proposed for Eriocaulon. This study aims to critically assess the existing infrageneric classifications through phylogenetic reconstruction of infrageneric relationships, based on DNA sequence data of four chloroplast markers and one nuclear marker. There is little congruence between our molecular results and previous morphology-based infrageneric classifications. However, some similarities can be found, including Fyson’s sect. Leucantherae and Zhang’s sect. Apoda. Further phylogenetic studies, particularly focusing on less well sampled regions such as the Neotropics, will help provide a more global overview of the relationships in Eriocaulon and may enable suggesting the first global infrageneric classification.

     

Molecular evidence for hybrid origin of Aster chusanensis,an endemic species of Ulleungdo,Korea

Ulleungdo is a small volcanic island and harbors many endemic plant species. Aster chusanensis Lim et al., a recently discovered endemic species on the island was proposed to be derived from hybridization between A. pseudoglehnii Lim et al. and A. oharai Nakai. To test hybrid origin of A. chusanensis, we sequenced the nrITS and three non-coding regions of a plastid genome (trnL-F, rbcL-accD, and psbA-trnH) from eight accessions of A. chusanensis and 37 accessions of its putative parents. Extensive investigation of the genome of A. chusanensis using 160 nrITS PCR amplicon sequences confirmed co-occurrence of nrITS sequences of the parental species within all accessions sampled. The retention of intact parental nrITS types in the genomes of A. chusanensis suggests that hybrid speciation has occurred recently on the island. The plastid DNA sequence data indicate that all of the hybrid individuals inherit the plastid from A. pseudoglehnii, except for one, which has the plastid of A. oharai, implying bidirectional but highly biased hybridization events during the evolution of A. chusanensis. Results of this study suggest that hybridization is an important process in the diversification of indigenous plants on Ulleungdo.     

Aster chusanensis (Asteraceae), a new species from Korea

Asterchusanensis is described and illustrated, and compared with its most closely related species,A. pseudoglehni andA. spathulifolius. This new species differs markedly from the latter two by its unequal inner and outer phyllaries, pubescent stem, leaves, and corolla tube, and ray florets partly in two series.     

Molecular Systematic Study of <Emphasis Type="Italic">Chrysosplenium</Emphasis> Series <Emphasis Type="Italic">Pilosa</Emphasis> (Saxifragaceae) in Korea

To address systematic issues pertaining to series Pilosa of Korean Chrysosplenium, the phylogenetic relationships of the 35 accessions of Korean Chrysosplenium taxa were examined using the DNA sequence data obtained from the nuclear ribosomal internal transcribed spacer (ITS) regions and the psbK-I gene of the plastid genome. The results from both ITS and psbK-I sequence data indicated that Chrysosplenium flaviflorum formed a well-supported clade that merits species status of the taxon. The ITS phylogenetic trees detected two distinct lineages in Chrysosplenium pilosum var. fulvum. Geographically, one lineage was widely distributed throughout the country whereas the other was confined to Gyeonggi and Gangwon provinces. The plants sampled from Jeju Island, which have been recognized as C. pilosum var. sphaerospermum [C. hallaisanense] exhibited no DNA sequence feature segregating them from C. pilosum var. fulvum [C. barbatum] distributed in the mainland area of Korea. The plastid DNA sequence data was not fully in concordance with the nuclear ribosomal ITS data and the current taxa delimitation. These results suggest incomplete lineage sorting or that plastid genome capture may have occurred during the evolution of some taxa examined in the present study.     

Taxonomic and phytogeographic implications from ITS phylogeny in<Emphasis Type="Italic"> Berberis</Emphasis> (Berberidaceae)

A phylogeny based on the internal transcribed spacer (ITS) sequences from 79 taxa representing much of the diversity of Berberis L. (four major groups and 22 sections) was constructed for the first time. The phylogeny was basically congruent with the previous classification schemes at higher taxonomic levels, such as groups and subgroups. A notable exception is the non-monophyly of the group Occidentales of compound-leaved Berberis (previously separated as Mahonia). At lower levels, however, most of previous sections and subsections were not evident especially in simple-leaved Berberis. Possible relationship between section Horridae (group Occidentales) and the simple-leaved Berberis clade implies paraphyly of the compound-leaved Berberis. A well-known South America-Old World (mainly Asia) disjunctive distribution pattern of the simple-leaved Berberis is explained by a vicariance event occurring in the Cretaceous period. The ITS phylogeny also suggests that a possible connection between the Asian and South American groups through the North American species (Berberis canadensis or B. fendleri) is highly unlikely.     

Female hyper IgM syndrome type 1 with a chromosomal translocation disrupting CD40LG

Hyper-IgM syndrome type 1 (HIGM1) is a primary immunodeficiency characterized by recurrent bacterial and opportunistic infections, associated with normal or high serum level of IgM and decreased serum levels of IgG, IgA and IgE due to the defect of class switch recombination. CD40LG, located in Xq26, has been reported to be mutated in male HIGM1 patients. Here, we report the second case of a female HIGM1 with the defect of CD40 ligand (CD40L) expression and of soluble serum CD40L. Clinical course and HIGM phenotype was indistinguishable from that of male HIGM1 including severe neutropenia. High-resolution chromosome banding revealed that this patient's karyotype is 46, X, t(X;14)(q26.3;q13.1), and FISH analysis demonstrated that the break point of the chromosomal translocation is within CD40LG. Using four chimeric cDNA clones obtained by 3' RACE method, the break point was identified within the intron 4 of CD40LG on X chromosome and non-coding region of chromosome 14. We also found an extremely skewed X-chromosome inactivation pattern by methylation-specific PCR. Thus, the reciprocal translocation caused the disruption of CD40LG, resulting in defective CD40L expression in the female patient with an extremely skewed X-inactivation pattern in T cells leading to the HIGM1 phenotype.