Genetic diversity of three Elymus species indigenous to Japan and East Asia (E. tsukushiensis, E. humidus and E. dahuricus) detected by AFLP.
(1/11)
With the aim of broadening the gene pool of Triticeae for crop improvement, the genetic diversity of three hexaploid Elymus species indigenous to Japan and East Asia (E. tsukushiensis, E. humidus and E. dahuricus) was evaluated using amplified fragment length polymorphism (AFLP) markers. A total of 34 accessions: five of E. tsukushiensis, 13 of E. humidus, 15 of E. dahuricus, and one tetraploid Elymus species as an outgroup, were analyzed. The AFLP analysis was conducted with 12 selective primer combinations. In all, 329 bands were scored. The average number of bands scored per accession was 135.3. Among the 34 accessions, no polymorphism was detected among 10 accessions of E. humidus and among three accessions of E. tsukushiensis. Each species showed a diagnostic band pattern. One accession of E. humidus showed a band pattern intermediate between those of E. humidus and E. tsukushiensis, suggesting the occurrence of interspecific introgression. The level of intraspecific variation was highest in E. dahuricus (1-psb = 0.17, pi = 0.010), followed by E. tsukushiensis (1-psb = 0.14, pi = 0.008) and E. humidus (1-psb = 0.03, pi = 0.002). The level of interspecific variation was higher than that of intraspecific variation in all the pairs compared. The level of divergence between E. humidus and E. tsukushiensis was relatively low, but even so it was two times higher than that of the intraspecific variation for each species. The phylogenetic tree constructed here showed clear separations of all the species. The results of this study indicate a clear divergence of E. humidus from E. tsukushiensis in spite of the morphological similarity between these two species. Based on the values of nucleotide diversity, the time of divergence between E. humidus and E. tsukushiensis was estimated to be 0.9-1.2 million years ago. (+info)
Isolation and characterization of bacteria associated with two sand dune plant species, Calystegia soldanella and Elymus mollis.
(2/11)
Little is known about the bacterial communities associated with the plants inhabiting sand dune ecosystems. In this study, the bacterial populations associated with two major sand dune plant species, Calystegia soldanella (beach morning glory) and Elymus mollis (wild rye), growing along the costal areas in Tae-An, Chungnam Province, were analyzed using a culture-dependent approach. A total of 212 bacteria were isolated from the root and rhizosphere samples of the two plants, and subjected to further analysis. Based on the analysis of the 16S rDNA sequences, all the bacterial isolates were classified into six major phyla of the domain Bacteria. Significant differences were observed between the two plant species, and also between the rhizospheric and root endophytic communities. The isolates from the rhizosphere of the two plant species were assigned to 27 different established genera, and the root endophytic bacteria were assigned to 21. Members of the phylum Gammaproteobacteria, notably the Pseudomonas species, comprised the majority of both the rhizospheric and endophytic bacteria, followed by members of Bacteroidetes and Firmicutes in the rhizosphere and Alphaproteobacteria and Bacteroidetes in the root. A number of isolates were recognized as potentially novel bacterial taxa. Fifteen out of 27 bacterial genera were commonly found in the rhizosphere of both plants, which was comparable to 3 out of 21 common genera in the root, implying the host specificity for endophytic populations. This study of the diversity of culturable rhizospheric and endophytic bacteria has provided the basis for further investigation aimed at the selection of microbes for the facilitation of plant growth. (+info)
Chryseobacterium soldanellicola sp. nov. and Chryseobacterium taeanense sp. nov., isolated from roots of sand-dune plants.
(3/11)
Two Gram-negative, yellow-pigmented bacteria designated PSD1-4T and PHA3-4T, isolated from two sand-dune plant species inhabiting coastal areas in Tae-an, Korea, were subjected to taxonomic investigation. 16S rRNA gene sequence analysis indicated that both isolates should be placed in the genus Chryseobacterium of the family Flavobacteriaceae. The phenotypic properties of the strains were also consistent with their classification into this genus. The levels of 16S rRNA gene sequence similarity between strain PSD1-4T and other Chryseobacterium species were 95.2-97.2%; those between PHA3-4T and others were 93.7-97.8%. The DNA-DNA relatedness data indicated that strains PSD1-4T and PHA3-4T were clearly different from the nearest species, Chryseobacterium indoltheticum and Chryseobacterium taichungense. The major fatty acids were 13-methyltetradecanoic acid (iso-C15:0), 3-hydroxy-15-methylhexadecanoic acid (iso-C17:0 3-OH) and omega-9-cis-15-methylhexadecenoic acid (iso-C17:1omega9c) for both strains. On the basis of polyphasic taxonomic analysis results, it is evident that each of these strains represents a novel species of Chryseobacterium, for which the names Chryseobacterium soldanellicola sp. nov. (type strain PSD1-4T=KCTC 12382T=NBRC 100864T) and Chryseobacterium taeanense sp. nov. (type strain PHA3-4T=KCTC 12381T=NBRC 100863T) are proposed. (+info)
Predicting germination response to temperature. II. Three-dimensional regression, statistical gridding and iterative-probit optimization using measured and interpolated-subpopulation data.
(4/11)
BACKGROUND AND AIMS: Most current thermal-germination models are parameterized with subpopulation-specific rate data, interpolated from cumulative-germination-response curves. The purpose of this study was to evaluate the relative accuracy of three-dimensional models for predicting cumulative germination response to temperature. Three-dimensional models are relatively more efficient to implement than two-dimensional models and can be parameterized directly with measured data. METHODS: Seeds of four rangeland grass species were germinated over the constant-temperature range of 3 to 38 degrees C and monitored for subpopulation variability in germination-rate response. Models for estimating subpopulation germination rate were generated as a function of temperature using three-dimensional regression, statistical gridding and iterative-probit optimization using both measured and interpolated-subpopulation data as model inputs. KEY RESULTS: Statistical gridding is more accurate than three-dimensional regression and iterative-probit optimization for modelling germination rate and germination time as a function of temperature and subpopulation. Optimization of the iterative-probit model lowers base-temperature estimates, relative to two-dimensional cardinal-temperature models, and results in an inability to resolve optimal-temperature coefficients as a function of subpopulation. Residual model error for the three-dimensional model was extremely high when parameterized with measured-subpopulation data. Use of measured data for model evaluation provided a more realistic estimate of predictive error than did evaluation of the larger set of interpolated-subpopulation data. CONCLUSIONS: Statistical-gridding techniques may provide a relatively efficient method for estimating germination response in situations where the primary objective is to estimate germination time. This methodology allows for direct use of germination data for model parameterization and automates the significant computational requirements of a two-dimensional piece-wise-linear model, previously shown to produce the most accurate estimates of germination time. (+info)
Proteome response of Elymus elongatum to severe water stress and recovery.
(5/11)
Tall wheatgrass (Elymus elongatum Host) is a drought-tolerant, cool-season forage grass native to Iran. A proteomic approach has been applied to identify mechanisms of drought responsiveness and tolerance in plants undergoing vegetative stage drought stress and then recovery after rewatering. Uniformed clones were reproduced from a parent plant collected from Brojen (central region of Iran). Clones were grown in pots and drought was initiated by withholding water for 16 d. The leaf samples were taken in triplicate from both stressed/rewatered plants and continuously watered controls at five times: (i) 75% FC, (ii) 50% FC, (iii) 25% FC, (iv) 3 d after rewatering, and (v) 14 d after rewatering. Changes in the proteome pattern of shoots were studied using two-dimensional gel electrophoresis. Following the 16 d water stress, both shoot dry weight and leaf width decreased up to 67% compared with the well-watered plants, whereas proline content increased up to 20-fold. Leaf relative water contents (RWC) also declined from 85% to 24%. Out of about 600 protein spots detected on any given two-dimensional gel, 58 protein spots were reproducibly and significantly changed during drought stress and recovery. Only one protein (abscisic acid- and stress-inducible protein) showed significant changes in expression and position in response to severe drought. The fifty-eight responsive proteins were categorized in six clusters including two groups of proteins specifically up- and down-regulated in response to severe drought stress. Eighteen proteins belonging to these two groups were analysed by liquid chromatography tandem mass spectrometry leading to the identification of 11 of them, including the oxygen-evolving enhancer protein 2, abscisic acid- and stress-inducible protein, several oxidative stress tolerance enzymes, two small heat shock proteins, and Rubisco breakdown. The results suggest that E. elongatum may tolerate severe drought stress by accumulating proline and several proteins related to drought-stress tolerance. Recovery after rewatering might be another mechanism by which plants tolerate erratic rainfall in semi-arid regions. (+info)
The origin of a "zebra" chromosome in wheat suggests nonhomologous recombination as a novel mechanism for new chromosome evolution and step changes in chromosome number.
(6/11)
Distinct origin of the Y and St genome in Elymus species: evidence from the analysis of a large sample of St genome species using two nuclear genes.
(7/11)