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PubMed1990

Numerical analysis of 295 phenotypic features of 266 Xanthomonas strains and related strains and an improved taxonomy of the genus.

An extensive phenotypic description and an improved classification and nomenclature of the genus Xanthomonas are presented. A total of 266 strains obtained from different geographical areas, including representative strains of all species of the genus Xanthomonas and most pathovars of Xanthomonas campestris, as well as strains which might be genetically related to the genus Xanthomonas, were examined for 295 morphological, biochemical, and physiological features. Similarities among the strains were expressed numerically by using the coefficient of Sokal and Michener. Clustering was performed by using the unweighted average pair group method. The conclusions described below were reached. (i) The genus Xanthomonas comprises at least the following eight phena: X. campestris, Xanthomonas albilineans, Xanthomonas axonopodis, Xanthomonas fragariae, Xanthomonas populi, Xanthomonas maltophilia, Xanthomonas oryzae Swings et al. 1990, and X. campestris pv. graminis Egli and Schmidt 1982 [not X. campestris pv. graminis (Egli et al. 1975) ISPP List 1980]. (ii) X. populi (Ridé 1958) Ridé and Ridé 1978 is a separate species. (iii) X. maltophilia Swings et al. 1983 forms a separate species. (iv) X. campestris pv. oryzae ISPP List 1980 can no longer be regarded as pathovar of X. campestris, and its recent reclassification as a new species, X. oryzae (Swings et al., Int. J. Syst. Bacteriol. 40:309-311, 1990), is supported. (v) X. campestris pv. graminis Egli and Schmidt 1982 [not X. campestris pv. graminis (Egli et al. 1975) ISPP List 1980] seems to form a separate complex of highly related pathovars obtained from members of the Poaceae; the taxonomic implications of this are discussed. (vi) Strains of nearly all X. campestris pathovars cluster together in the X. campestris phenon. Within this species we were able to differentiate some entities on phenotypic grounds; these groups sometimes corresponded to named pathovars (e.g., X. campestris pv. manihotis, X. campestris pv. cassavae, X. campestris pv. phlei). In several other cases, pathovars were found to be heterogeneous. (vii) A number of dubious Pseudomonas species were identified as members of or as being close to Xanthomonas species. Both Pseudomonas betle and Pseudomonas hibiscicola are synonyms of X. maltophilia. We also confirmed that Pseudomonas mangiferaeindicae, Pseudomonas vitiswoodrowii, and Pseudomonas gardneri belong to X. campestris. (viii) Forty phenotypic features allow the differentiation of the eight Xanthomonas phena. (ix) A number of additional features of the genera Xanthomonas and Xylophilus are described.

Base Composition↗
PubMed2024

Premeiotic 24-nt phasiRNAs are present in the Zea genus and unique in biogenesis mechanism and molecular function.

Reproductive phasiRNAs are broadly present in angiosperms and play crucial roles in sustaining male fertility. While the premeiotic 21-nt phasiRNAs and meiotic 24-nt phasiRNA pathways have been extensively studied in maize (Zea mays) and rice (Oryza sativa), a third putative category of reproductive phasiRNAs-named premeiotic 24-nt phasiRNAs-have recently been reported in barley (Hordeum vulgare) and wheat (Triticum aestivum). To determine whether premeiotic 24-nt phasiRNAs are also present in maize and related species and begin to characterize their biogenesis and function, we performed a comparative transcriptome and degradome analysis of premeiotic and meiotic anthers from five maize inbred lines and three teosinte species/subspecies. Our data indicate that a substantial subset of the 24-nt phasiRNA loci in maize and teosinte are already highly expressed at premeiotic phase. The premeiotic 24-nt phasiRNAs are similar to meiotic 24-nt phasiRNAs in genomic origin and dependence on DCL5 for biogenesis, however, premeiotic 24-nt phasiRNAs are unique in that they are likely (i) not triggered by microRNAs, (ii) not loaded by AGO18 proteins, and (iii) not capable of mediating cis-cleavage. In addition, we also observed a group of premeiotic 24-nt phasiRNAs in rice using previously published data. Together, our results indicate that the premeiotic 24-nt phasiRNAs constitute a unique class of reproductive phasiRNAs and are present more broadly in the grass family (Poaceae) than previously known.

Maize↗
PubMed2025

Grains, trade and war in the multimodal transmission of Rice yellow mottle virus: An historical and phylogeographical retrospective.

Rice yellow mottle virus (RYMV) is a major pathogen of rice in Africa. RYMV has a narrow host range limited to rice and a few related poaceae species. We explore the links between the spread of RYMV in East Africa and rice history since the second half of the 19th century. The phylogeography of RYMV in East Africa was reconstructed from coat protein gene sequences (ORF4) of 335 isolates sampled over two million square kilometers between 1966 and 2020. Dispersal patterns obtained from ORF2a and ORF2b, and full-length sequences converged to the same scenario. The following imprints of rice cultivation on RYMV epidemiology were unveiled. RYMV emerged in the middle of the 19th century in the Eastern Arc Mountains where slash-and-burn rice cultivation was practiced. Several spillovers from wild hosts to cultivated rice occurred. RYMV was then rapidly introduced into the nearby large rice growing Kilombero valley and Morogoro region. Harvested seeds are contaminated by debris of virus infected plants that subsist after threshing and winnowing. Long-distance dispersal of RYMV is consistent (i) with rice introduction along the caravan routes from the Indian Ocean Coast to Lake Victoria in the second half of the 19th century, (ii) seed movement from East Africa to West Africa at the end of the 19th century, from Lake Victoria to the north of Ethiopia in the second half of the 20th century and to Madagascar at the end of the 20th century, (iii) and, unexpectedly, with rice transport at the end of the First World War as a troop staple food from the Kilombero valley towards the South of Lake Malawi. Overall, RYMV dispersal was associated to a broad range of human activities, some unsuspected. Consequently, RYMV has a wide dispersal capacity. Its dispersal metrics estimated from phylogeographic reconstructions are similar to those of highly mobile zoonotic viruses.

Oryza↗
PubMed1989

An improved method for studying grass leaf epidermis.

Leaf epidermis of grasses is elaborate and important in the systematics of the Poaceae at subfamily and genus level. Most available techniques used in preparing leaf epidermis for microscopic studies are time-consuming and often produce preparations inadequate for studying histological detail. A combination of the hand scraping and maceration methods with modifications is proposed in this paper to prepare epidermal peels comparatively rapidly. One epidermal layer was scraped off and the mesophyll tissue removed from the epidermis to be studied by maceration in HNO3. The recovered epidermal peel was neutralized in NaOH and stained with malachite green or safranin O. Preparations made by this technique are suitable for studies of epidermal features, measurements of special structures and determinations of trichome indices. This method has been used in a study investigating intraspecific variation in southern African pasture grasses.

Histological Techniques↗
PubMed2026

Mitogenome assembly and phylogenetic relationships of Phalaris arundinacea.

INTRODUCTION: As a perennial herb of Poaceae, Phalaris arundinacea plays key roles in grazing, production, and soil and water conservation because of its well-developed rhizomes and seed dispersal. We assembled and annotated the first mitogenome of P. arundinacea to support evolutionary and taxonomic research. METHODS: We assembled and annotated the first complete mitochondrial genome of P. arundinacea by integrating Illumina short reads with Nanopore long reads via a hybrid assembly strategy. The genome architecture was comprehensively characterized, encompassing codon usage bias, repetitive sequence organization, and inter-organellar genetic exchange with the chloroplast genome. RESULTS AND DISCUSSION: Assembly of the P. arundinacea mitogenome revealed two circular structures with a combined length of 526,717 bp. The genome comprised a set of 37 protein-coding genes (PCGs), 27 tRNAs, and 8 rRNAs, with the rRNA genes exhibiting full assembly (100% coverage). The mitochondrial genome contained 154 forward and 164 palindromic repeats, along with 25 tandem repeats and 124 simple sequence repeats (SSRs). Notably, 102 SSRs were distributed on contig1, predominantly in tetrameric form. Furthermore, 376 RNA editing sites were predicted. A total of 104 fragments were integrated into the mitochondrial genome from the chloroplast, amounting to 55,866 bp of transferred sequence. Finally, phylogenetic analysis of 28 plant mitogenomes placed P. arundinacea closest to species within the genus Poa (P. chaixii and P. pratensis). Comparative analysis of non-synonymous-to-synonymous substitution rate (Ka/Ks) ratios across divergent species revealed that the mitochondrial genome of P. arundinacea underwent stabilizing evolutionary dynamics, characterized by predominant purifying selection with several lineage-specific variations in selective pressure. Our findings support the close phylogenetic relationship between P. arundinacea and species of the genus Poa and provide a reference mitochondrial genome resource for future comparative studies within Phalaris that incorporate broader taxon sampling. These results support deeper phylogenetic investigations of P. arundinacea and facilitate future work on its germplasm characterization and applied use.

Phalaris arundinacea↗
PubMed1988

[Hyposensitization with cross-reacting pollen allergens].

Grass-pollen are one of the most common allergens in pollinosis. Rye-pollen are the most important allergens among cereals-pollen in Germany. Between pollen-allergens, the phenomenon of cross-sensitivity is well-known. In the RAST und RAST-Inhibitionstest the cross-sensitivity between grass-pollen and rye-pollen is well documentated. In the clinic the test and challenge with some grass-pollen ist suitable for the diagnosis and planing of therapy. Therefore, it seems, that therapy with grass-pollen should produce the same results as a treatment with grass- and rye-pollen. We treated 35 patients allergic with poaceae-pollen for 3 years in two different ways: One group we treated only with grass-pollen, the other group we treated with grass- and rye-pollen. Under the therapy we controlled the specific IgE and IgG, the nasal challenge-test and the subjective symptoms by diaries and questionnaires. The specific IgE for phleum pratense and rye-pollen decreased, the specific IgG increased in both groups. There were no differences between the two therapy-groups. In the clinical data-subjective and nasal challenge-the therapeutic effect seemed to be better in the group treated with grass- and rye-pollen.

Adult↗
PubMed1987

Survey of airborne pollen and fungal spores at Dehra Dun, India.

A survey of airborne pollen and fungal spores was carried out using a gravity settling device at Dehra Dun for two consecutive years (1980-81). The daily, seasonal, and annual variations recorded for the dominant pollen and spore types are analysed in detail. Two distinct peak pollen periods, February-April and August-October, have been recognized although pollen was found present in the atmosphere throughout the year. In contrast, fungal spores did not exhibit any distinct seasonal pattern. July through October has been observed as the period of higher spore catch as compared to other months. Pollen grains of Pinus are recorded as the most dominant type at Dehra Dun followed by Broussonetia, Rosaceae, Poaceae, Debregeasia, Rumex, and Morus. Among fungal types, Cladosporium, Alternaria, smut spores, Curvularia, Ascospores, Nigrospora, Aspergilli/Penicilli, and Epicoccum dominated the atmosphere in order of their prevalence.

Air Microbiology↗
PubMed1975

A human model of allergic conjunctivitis.

Using the method of refractometry to measure protein concentration in tears, a simple model was developed to evaluate the allergic response in humans. Timothy grass pollen was instilled into the cul de sac of a human subject, and the protein content of the subject's tears was sampled every 15 minutes for three hours. Once the time course of this experiment was predictable, various eye medications were instilled into the subject's eye 30 minutes after allergic challenge. It was noted that 1.0% and 0.1% prednisolone, each combined with 0.12% phenylephrine hydrochloride, as well as 1% epinephryl borate eye drops, produced an almost immediate return to normal of tear protein levels, whereas 1.0% medrysone, 0.1% fluorometholone, 1.0% prednisolone, and 0.12% prednisolone had less pronounced effects on reduction of elevated tear protein concentration.

Administration, Topical↗
PubMed1986

Silica in higher plants.

Opaline silica deposits are formed by many vascular (higher) plants. The capacity of these plants for silica absorption varies considerably according to genotype and environment. Plant communities exchange silica between soil and vegetation, especially in warmer climates. Silica deposition in epidermal cell walls offers mechanical and protective advantages. Biogenic silica particles from plants are also implicated in the causation of cancer. Recent techniques are reviewed which may aid in the identification of plant pathways for soluble silica movement to deposition sites and in the determination of ionic environments. Botanical investigations have focused on silicification of cell walls in relation to plant development, using scanning and transmission electron microscopy combined with X-ray microanalysis. Silica deposition in macrohair walls of the lemma of canary grass (Phalaris) begins at inflorescence emergence and closely follows wall thickening. The structure of the deposited silica may be determined by specific organic polymers present at successive stages of wall development. Lowering of transpiration by enclosure of Phalaris inflorescences in plastic bags reduced silica deposition in macrohairs. Preliminary freeze-substitution studies have located silicon, as well as potassium and chloride, in the cell vacuole and wall deposition sites during initial silicification.

Climate↗
PubMedDate not supplied

Phosphorus cycles of forest and upland grassland ecosystems and some effects of land management practices.

The distribution of phosphorus capital and net annual transfers of phosphorus between the major components of two unfertilized phosphorus-deficient UK ecosystems, an oak--ash woodland in the Lake District and an Agrostis-Festuca grassland in Snowdonia (both on acid brown-earth soils), have been estimted in terms of kg P ha--1. In both ecosystems less than 3% of the phosphorus, totalling 1890 kg P ha--1 and 3040 kg P ha--1 for the woodland and grassland, respectively, is contained in the living biomass and half that is below ground level. Nearly all the phosphorus is in the soil matrix. Although the biomass phosphorus is mostly in the vegetation, the soil fauna and vegetation is slower (25%) than in the grassland vegetatation (208%). More than 85% of the net annual vegetation uptake of phosphorus from the soil is returned to the soil, mainly in organic debris, which in the grassland ecosystem is more than twice as rich in phosphorus (0.125% P) as in the woodland ecosystem (0.053% P). These concentrations are related to the rates of turnover (input/P content) of phosphorus in the litter layer on the soil surface; it is faster in the grassland (460%) than in the woodland (144%). In both cycles plant uptake of phosphorus largely depends on the release of phosphorus through decomposition of the organic matter returned to soil. In both the woodland and the grassland, the amount of cycling phosphorus is potentially reduced by its immobilization in tree and sheep production and in undecomposed organic matter accumulating in soil. It is assumed that the reductions are counterbalanced by the replenishment of cycling phosphorus by (i) some mineralization of organically bound phosphorus in the mineral soil, (ii) the income in rainfall and aerosols not being effectively lost in soil drainage waters and (iii) rock weathering. The effects of the growth of conifers and sheep grazing on the balance between decomposition and accumulation of organic matter returned to soil are considered in relation to the rate of phosphorus cycling and the pedogenetic changes in soil phosphorus condition leading to reduced fertility. Although controlled sheep grazing speeds up phosphorus cycling and may reverse the pedogenetic trend in favour of soil improvement, conifers may slow down phosphorus cycling and promote the pedogenetic trend towards infertility.

Agriculture↗
PubMed1986

Hazardous agents in agricultural dusts and methods of evaluation.

Organic dusts in agriculture vary with type of agriculture, weather conditions, geographical location, and agricultural practices. It is difficult to ascribe a specific biological effect to a specific agent in agricultural dusts, and we are only able to develop a list of candidates for disease-causing agents. Future studies should be designed to define more specifically the hazardous agents in agricultural dusts by using more precise analytical techniques and documenting the clinical effects to man, developing dose-response relationships.

Agricultural Workers' Diseases↗
PubMedDate not supplied

Reactivities of immunoglobulin E and immunoglobulin G subclasses identified by isoelectric focusing-immunoprint in allergic patients.

Probing of IgE or IgG subclass reactivities on single allergenic components in an extract is tedious and time-consuming under native conditions. Isoelectric focusing immunoblotting combines a powerful, highly resolving native separation method with the specificity and sensitivity of immunological test methods. This method is easy and quick to perform. The potential usefulness of this method is demonstrated by eight examples of a type I or type III allergy analyzing IgE and IgG subclass reactivities and their distribution.

Allergens↗
PubMedDate not supplied

Examination of microheterogeneity in grass pollen allergens.

The separation of timothy pollen extract by two-dimensional immunoblotting revealed microheterogeneity of the major allergens PhI p I and PhI p V. There was not only a diversity in size, 38 and 32 kDa for PhI p V and 37, 35, and 33 kDa for PhI p I, but also a separation into proteins of identical sizes but different pIs. Since former studies on the protein structure by amino acid analysis and N-terminal microsequencing did not reveal any differences, we examined other possibilities that might cause microheterogeneity. In allergens belonging to the PhI p I group, the variability in pI can be due to the carbohydrate structure and to the fact that charges are hidden in the interior of the protein, as shown by varying concentrations of urea. On the other hand we were not able to detect any such reasons for the existence of PhI p V isoallergens. Thus, we assume that they are stable conformational isomers of the proteins (allomorphism) or that there are only slight variations in the internal sequences of these proteins (polymorphism) causing distinct pIs.

Allergens↗