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PubMed2006

Evolution of unisexual flowers in grasses (Poaceae) and the putative sex-determination gene, TASSELSEED2 (TS2).

Unisexuality has evolved repeatedly in flowering plants, but its genetic control is not understood in most cases. In maize (Zea mays), unisexual flower development is regulated by a short-chain dehydrogenase/reductase protein, TASSELSEED2 (TS2), but its role in other grass lineages is unknown. TS2 was cloned and sequenced from a broad range of grasses and compared to available sequences from other flowering plants using phylogenetic analysis and tests for selection. Gene expression was investigated using reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization. TS2 orthologs appear to be restricted to monocots. The TS2 protein sequence was found to be generally under purifying selection in bisexual and unisexual lineages alike. Only one site, in unisexual herbaceous bamboos, is potentially under positive selection. TS2 was expressed broadly in all sampled tissues of unisexual and bisexual grasses, and was also expressed in rice flowers in floral organs that do not abort. TS2 may have a more general developmental role in most grasses than programmed cell death of the developing gynoecium, but has been co-opted to this role within a subset of Poaceae, probably as a result of alterations in the activity or regulation of other genes in the gynoecial pathway.

Amino Acid Sequence↗
PubMed2007

Endosperm formation in aposporous Crataegus (Rosaceae, Spiraeoideae, tribe Pyreae): parallels to Ranunculaceae and Poaceae.

Apomixis in Crataegus is primarily aposporous and requires pollination. The embryo sac is of the Polygonum type. A combination of meiotically unreduced embryo sacs with apparently reduced pollen would violate the usual requirement for a 2 : 1 ratio of maternal to paternal contributions to the endosperm. We therefore investigated the origin of endosperm in seeds of sexual diploids and apomictic polyploids of the sister genera Crataegus and Mespilus. Flow-cytometric DNA measurements from embryo and endosperm in mature seeds were converted to ploidy levels using leaf-tissue information. The diploids had triploid endosperm. In c. 60% of seed from polyploids, one sperm apparently contributes to the endosperm, while 25% or more may involve two sperm. Additional results suggest that trinucleate central cells also occur. Fertilization of meiotically unreduced eggs is indicated. The ratio of maternal to paternal contributions to the endosperm in these apomictic Crataegus is not constrained to 2 : 1. They thus resemble some Sorbus (Pyreae) and very distantly related Ranunculus (Ranunculaceae). It is suggested that Paspalum (Poaceae) may have similarly flexible endosperm ploidy levels.

Crataegus↗
PubMed2002

An enhanced molecular marker based genetic map of perennial ryegrass (Lolium perenne) reveals comparative relationships with other Poaceae genomes.

A molecular-marker linkage map has been constructed for perennial ryegrass (Lolium perenne L.) using a one-way pseudo-testcross population based on the mating of a multiple heterozygous individual with a doubled haploid genotype. RFLP, AFLP, isoenzyme, and EST data from four collaborating laboratories within the International Lolium Genome Initiative were combined to produce an integrated genetic map containing 240 loci covering 811 cM on seven linkage groups. The map contained 124 codominant markers, of which 109 were heterologous anchor RFLP probes from wheat, barley, oat, and rice, allowing comparative relationships between perennial ryegrass and other Poaceae species to be inferred. The genetic maps of perennial ryegrass and the Triticeae cereals are highly conserved in terms of synteny and colinearity. This observation was supported by the general agreement of the syntenic relationships between perennial ryegrass, oat, and rice and those between the Triticeae and these species. A lower level of synteny and colinearity was observed between perennial ryegrass and oat compared with the Triticeae, despite the closer taxonomic affinity between these species. It is proposed that the linkage groups of perennial ryegrass be numbered in accordance with these syntenic relationships, to correspond to the homoeologous groups of the Triticeae cereals.

Chromosome Mapping↗
PubMed1995

Phylogenetic relationships of the monogenomic species of the wheat tribe, Triticeae (Poaceae), inferred from nuclear rDNA (internal transcribed spacer) sequences.

Phylogenetic relationships of 30 diploid species of Triticeae (Poaceae) representing 19 genomes were estimated from the sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. The ITS sequence phylogeny indicated that: (i) each genome group of species is monophyletic, concordant with cytogenetic evidence; (ii) Hordeum (I) and Critesion (H) are basal; (iii) Australopyrum (W) is closely related to Agropyron (P); (iv) Peridictyon (G), Heteranthelium (Q), and Dasypyrum (V) are closely related to Pseudoroegneria (S); (v) most of the annuals, Triticum s.l. (A, B, D), Crithopsis (K), Taeniatherum (T), Eremopyrum (F), Henrardia (O), Secale (R), and two perennials, Thinopyrum (J) and Lophopyrum (E), all of Mediterranean origin, are a monophyletic group. However, phylogenetic trees based on morphology group these Mediteranean species with various perennial lineages of the Arctic-temperate region. The molecular data and biogeography of the tribe suggest that the Mediterranean lineage is derived from the Arctic-temperate lineage and that the two lineages have evolved in parallel. Extensive morphological parallelism apparently obscures the true genealogical history of the tribe when only morphology is considered.

Africa, Northern↗
PubMed1997

On the origins of the tetraploid Bromus species (section Bromus, Poaceae): insights from internal transcribed spacer sequences of nuclear ribosomal DNA.

The internal transcribed spacer (ITS) region of nuclear ribosomal DNA from 22 diploid and tetraploid annual Bromus species of section Bromus (Poaceae) and three species belonging to other Bromus sections, Bromus catharticus (section Ceratochloa), Bromus anomalus (section Pnigma), and Bromus sterilis (section Genea), were investigated by PCR amplification and direct sequencing. The length of the ITS-1 region varied from 215 to 218 bp, and that of the ITS-2 region from 215 to 216 bp, in the species analyzed. ITS-1 was more variable and provided more informative sites (49) than ITS-2 (32). No variation was encountered within species. In pairwise comparison among species of section Bromus, sequence divergence ranged from 0.0 to 8.0% for the combined ITS-1 and ITS-2 regions. Parsimony analysis using Avena longiglumis and Hordeum vulgare as outgroups resulted in well-resolved phylogenetic trees and showed that section Bromus is monophyletic according to the species analyzed outside of the section. The analysis clarified the phylogenetic relationships among monogenomic (diploid) species. Introduction of the allotetraploid species did not change the general topology of the trees obtained using only the diploid species. Although some tetraploid-diploid species relationships will have to be clarified with faster evolving markers, the ITS sequences are shown to be useful for assessing evolutionary relationships among closely related Bromus species, as well as for clarifying taxonomic problems in previously controversial cases (e.g., Bromus alopecuros and Bromus caroli-henrici). New hypotheses are proposed concerning the origin of several allotetraploid species. For example, it is shown that the tetraploid Bromus hordeaceus diverged earlier than all other species of section Bromus, excluding the diploid B. caroli-henrici, which is found to be basal in this group. The tetraploid Bromus arenarius, which was considered a hybrid between sections Bromus and Genea, and the tetraploid Bromus adoensis are sister taxa within section Bromus; they belong in a weakly differentiated clade with the diploids Bromus brachystachys, Bromus japonicus, Bromus squarrosus, Bromus arvensis, and Bromus intermedius.

DNA, Plant↗
PubMed2004

Comparative mapping of a major aluminum tolerance gene in sorghum and other species in the poaceae.

In several crop species within the Triticeae tribe of the grass family Poaceae, single major aluminum (Al) tolerance genes have been identified that effectively mitigate Al toxicity, a major abiotic constraint to crop production on acidic soils. However, the trait is quantitatively inherited in species within other tribes, and the possible ancestral relationships between major Al tolerance genes and QTL in the grasses remain unresolved. To help establish these relationships, we conducted a molecular genetic analysis of Al tolerance in sorghum and integrated our findings with those from previous studies performed in crop species belonging to different grass tribes. A single locus, AltSB, was found to control Al tolerance in two highly Al tolerant sorghum cultivars. Significant macrosynteny between sorghum and the Triticeae was observed for molecular markers closely linked to putatively orthologous Al tolerance loci present in the group 4 chromosomes of wheat, barley, and rye. However, AltSB was not located within the homeologous region of sorghum but rather mapped near the end of sorghum chromosome 3. Thus, AltSB not only is the first major Al tolerance gene mapped in a grass species that does not belong to the Triticeae, but also appears to be different from the major Al tolerance locus in the Triticeae. Intertribe map comparisons suggest that a major Al tolerance QTL on rice chromosome 1 is likely to be orthologous to AltSB, whereas another rice QTL on chromosome 3 is likely to correspond to the Triticeae group 4 Al tolerance locus. Therefore, this study demonstrates a clear evolutionary link between genes and QTL encoding the same trait in distantly related species within a single plant family.

Aluminum↗
PubMed2002

[The Poaceae pollen season in France in 2001].

The aim of this study was to determine the main characteristics of the Poaceae pollen season in France (seasonal and daily quantities) in 2001, and to compare them to those of the previous years. The data came from seven volumetric Hirst traps, located in the cities of Amiens, Paris, Lyon, Nîmes, Bordeaux, Montluçon and Strasbourg. The study period range from the beginning of March to the end of August. The pollen quantities of 2001 were particularly high in three sites (Montluçon, Bordeaux et Lyon); they were higher than those of 2000 in Amiens and Strasbourg, but in those sites the peak of the whole series was situated in 1994; lastly the pollen quantities of 2001 were little different or lower than those of 2000 in Nîmes and Paris. This was probably not without effect on allergic people.

Air↗
PubMed1994

[Type I hypersensitivity to pollen of the Poaceae family (Gramineae), by tribe, in atopic dermatitis patients].

Type I Hypersensitivity to Poaceae pollen was tested in 27 Costa Rican patients with a clinical diagnosis of Atopic Dermatitis (six were males). Skin prick tests were done with 1/10 W/V, 50% glycerinated, pollen extracts, organized by tribes. Most patients had several allergic problems. Sensitivity increased with the number of allergic diagnoses. Positivity ranged from 25% in patients with Atopic Dermatitis exclusively to 100% in those with three or four simultaneous allergic illnesses. Andropogoneae was highest with 37% while the lower positivity was in the Paniceae (22.2%).

Adolescent↗
PubMed1988

Two-dimensional electrophoresis as a tool for structural and genetic studies of seed proteins from Poaceae and Fagaceae.

The application of two-dimensional electrophoretic procedures to structural and genetic studies of seed proteins from Poaceae (including the cultivated cereals) and Fagaceae is described. The following related problems have been considered: covalent and non-covalent association of protein subunits in multiple oligomeric structures; chromosomal locations of genes encoding seed proteins; quantitation of gene products in relation to gene expression and regulation; purification of protein components to study their homology relationships and in vitro activities; evolutionary and phylogenetic relationships; identification of genetic stocks. Isoelectric focusing, pore-gradient electrophoresis, electrophoresis at different pH's, are among the separation procedures used in the first dimension, whereas sodium dodecyl sulfate-polyacrylamide gel electrophoresis and starch-gel electrophoresis at acid pH have been the preferred second-dimensional methods. Dissociating conditions (sodium dodecyl sulfate, Nonidet P-40, or urea) and reducing conditions (2-mercaptoethanol) have been used when required.

Aneuploidy↗
PubMed1994

Molecular evolutionary characterization of an Activator (Ac)-like transposable element sequence from pearl millet (Pennisetum glaucum) (Poaceae).

We present data on the evolution of the Ac/Ds family of transposable elements in select grasses (Poaceae). A defective Ac-like element was cloned from a DNA library of the grass Pennisetum glaucum (pearl millet) and its entire 4531 bp sequence has been determined. When the pearl millet Ac-like sequence is aligned with the maize Ac sequence, it is found that there is approximately 70% DNA similarity in the central region spanning most of maize Ac exon II and all of exon III. In addition, there are two smaller regions of similarity at the Ac terminii. Besides these three major structural similarities, Pennisetum Ac has two large regions, one 5' and one 3', that show little similarity to Zea Ac. Furthermore, most of the sequences corresponding to intron II in maize Ac are absent in pearl millet Ac. Kimura's evolutionary distance between the central region of maize and pearl millet Ac sequences is estimated to be 0.429 +/- 0.020 nucleotide substitutions per site. This value is not significantly different from the average number of synonymous substitutions for coding regions of the Adh1 gene between maize and pearl millet, which is 0.395 +/- 0.051 nucleotide substitutions per site. If we assume Ac and Adh1 divergence times are equivalent between maize and pearl millet, then the above calculations suggest Ac-like sequences have probably not been strongly constrained by natural selection. Conserved DNA and amino acid sequence motifs are also examined. The level of DNA sequence divergence between maize and pearl millet Ac sequences, the estimated date when maize and pearl millet diverged (25-40 million years ago), coupled with their reproductive isolation/lack of current genetic exchange, all support the theory that Ac-like sequences have not been recently introduced into pearl millet from maize. Instead, Ac-like sequences were probably present in the progenitor of maize and pearl millet and have thus existed in the grasses for at least 25 million years.

Amino Acid Sequence↗
PubMed2002

Sequence variation in the gene encoding the 10-kDa prolamin in Oryza (Poaceae). I. Phylogenetic Implications.

Oryza L. (Poaceae) contains approximately 20 wild and two domesticated species and nine genomes. Major disagreements exist on its systematics and genome evolution. Sequence polymorphism in the gene that encodes the 10-kDa prolamin polypeptide (a seed storage protein) was used to determine phylogenetic relationships and evaluate current systematics for 19 Oryza species. This gene in Oryza is approximately 402-bp long, and includes a 72-bp signal peptide region. A strict consensus tree shows Oryza brachyantha (FF) as the most basal species, followed by a polytomy of three clades that can be delineated based on genome composition: (1) the GG clade: Oryza granulata and Oryza meyeriana, (2) the EE clade: Oryza australiensis, and (3) the ABCD clade: the remaining Oryza species. Two subclades within the ABCD clade emerge, one containing species with the AA genome, the other with components of the BC and D genomes. Members of the AA subclade form a polytomy and were delineated by a single 3-base deletion. The African species Oryza punctata (BB) and the South American-endemic CCDD genome species form a strong lineage, pointing to a close genetic affinity of O. punctata to the missing DD genome donor. The strong association between the CC and BBCC species implies convergence at the gene level. The study supports the following sectional units of Oryza: Section Oryza (Series sativae and officinaliae), Section australiensis, Section Granulata, Section Brachyantha.

Journal Article↗
PubMed2002

Growth promotion and an increase in cell wall extensibility by silicon in rice and some other Poaceae seedlings.

The effect of silicon on organ growth and its mechanisms of action were studied in rice ( Oryza sativa L. cv. Koshihikari), oat ( Avena sativa L. cv. Victory), and wheat ( Triticum aestivum L. cv. Daichino-Minori) seedlings grown in the dark. Applying silicon in the form of silicic acid to these seedlings via culture solution resulted in growth promotion of third (rice) or second (oat and wheat) leaves. The optimal concentration of silicon was 5-10 mM. No growth promotion was observed in early organs, such as coleoptiles or first leaves. In silicon-treated rice third leaves, the epidermal cell length increased, especially in the basal regions, without any effect on the number of cells, showing that silicon promoted cell elongation but not cell division. Silicon also increased the cell wall extensibility significantly in the basal regions of rice third leaves. These results indicate that silicon stimulates growth of rice and some other Poaceae leaves by increasing cell wall extensibility.

Journal Article↗
PubMed2007

Phylogenetic analysis of AA-genome Oryza species (Poaceae) based on chloroplast, mitochondrial, and nuclear DNA sequences.

Species in the genus Oryza (Poaceae) contain 10 genomic types and are distributed in pan-tropics of the world. To explore phylogenetic relationships of Oryza species having the AA-genome, DNA sequences of the chloroplast trnL intron and trnL-trnF spacer, mitochondrial nad1 intron 2, and nuclear internal transcribed spacer were analyzed, based on materials from 6 cultivated (O. sativa and O. glaberrima) and 13 wild accessions, in addition to a CC-genome species (O. officinalis) that was used as an outgroup. Analyses of the combined sequence data set from different sources provide a much better resolution of the AA-genome species than the individual data set, indicating the limitation of a single gene in phylogenetic reconstruction. The phylogeny based on the combined data set demonstrated an apparent grouping of the AA-genome Oryza species that was well associated with their geographic origin, although the Australian O. meridionalis showed its affinity with the African species. The geographic pattern of the phylogenetic relationship was probably attributed to the frequent genetic exchange and introgression among the AA-genome species from the same continents. In addition, Asian cultivated rice O. sativa showed its close relation to O. rufipogon and O. nivara, whereas African cultivated rice O. glaberrima was closely linked to O. barthii and O. longistaminata, indicating the independent domestication of the two cultivated species in different geographic locations.

Cell Nucleus↗
PubMed2004

Phylogenetic analysis of Hordeum (Poaceae) as inferred by nuclear rDNA ITS sequences.

Hordeum (Poaceae, Triticeae) occurs with 31 species worldwide in temperate regions, with the exception of Australasia. About 50% of the species are polyploids (4x, 6x) or occur as di- and polyploid forms. To analyze the phylogenetic relationships among diploid and polyploid taxa of the genus the nuclear rDNA internal transcribed spacer region (ITS) was analyzed for 91 accessions, representing all Hordeum species, together with 10 outgroup species. PCR products were either directly sequenced (outgroups) or cloned and eight clones per individual were analyzed. Phylogenetic analysis revealed four major clades that concur with the four genome groups in Hordeum (H, I, Xa, and Xu). Allopolyploids, putative autopolyploids, and species groups within the closely related H-genome clade could be identified. The ITS data indicate times of independent evolution of paralogous rDNA clusters on different chromosomes intermitted by sweeps of homogenization among these clusters and bi-directional homogenization of the clusters in diploids. Penalized likelihood analysis revealed an age of about 12 million years (my) for the genus and indicated the start of a rapid radiation in the H-genome group about 2.5 my ago in South America and Asia.

Cell Nucleus↗
PubMed2005

Localization of the 5S and 45S rDNA sites and cpDNA sequence analysis in species of the Quadrifaria group of Paspalum (Poaceae, Paniceae).

BACKGROUND AND AIMS: The Quadrifaria group of Paspalum (Poaceae, Paniceae) comprises species native to the subtropical and temperate regions of South America. The purpose of this research was to characterize the I genomes in five species of this group and to establish phylogenetic relationships among them. METHODS: Prometaphase chromatin condensation patterns, the physical location of 5S and 45S rDNA sites by fluorescence in situ hybridization (FISH), and sequences of five chloroplast non-coding regions were analysed. KEY RESULTS: The condensation patterns observed were highly conserved among diploid and tetraploid accessions studied and not influenced by the dyes used or by the FISH procedure, allowing the identification of almost all the chromosome pairs that carried the rDNA signals. The FISH analysis of 5S rDNA sites showed the same localization and a correspondence between the number of sites and ploidy level. In contrast, the distribution of 45S rDNA sites was variable. Two general patterns were observed with respect to the location of the 45S rDNA. The species and cytotypes Paspalum haumanii 2x, P. intermedium 2x, P. quadrifarium 4x and P. exaltatum 4x showed proximal sites on chromosome 8 and two to four distal sites in other chromosomes, while P. quarinii 4x and P. quadrifarium 2x showed only distal sites located on a variable number of small chromosomes and on the long arm of chromosome 1. The single most-parsimonious tree found from the phylogenetic analysis showed the Quadrifaria species partitioned in two clades, one of them includes P. haumanii 2x and P. intermedium 2x together with P. quadrifarium 4x and P. exaltatum 4x, while the other contains P. quadrifarium 2x and P. quarinii 4x. CONCLUSIONS: The subdivision found with FISH is consistent with the clades recovered with cpDNA data and both analyses suggest that the Quadrifaria group, as presently defined, is not monophyletic and its species belong in at least two clades.

Chromosomes, Plant↗
PubMed1993

Nucleotide polymorphism in the Adh1 locus of pearl millet (Pennisetum glaucum) (Poaceae).

We investigated nucleotide polymorphism in the Adh1 locus of pearl millet (Pennisetum glaucum) (Poaceae) by determining the DNA sequence of 20 alleles from 10 individuals. The individuals were sampled from throughout pearl millet's indigenous range and represent both wild and cultivated accessions. Our results indicated that there is little nucleotide polymorphism in the Adh1 locus. Estimates of per site nucleotide polymorphism did not differ significantly between cultivated and wild millet accessions. We compared nucleotide polymorphism in pearl millet Adh1 with nucleotide polymorphism in maize (Zea mays) Adh1 and conclude that the maize Adh1 sample is more polymorphic. Increased polymorphism in maize Adh1 may be attributable, in part, to faster substitution rates in the maize lineage. Analysis suggests that substitution rates in the maize Adh1 lineage are approximately 1.7 times faster than substitution rates in the millet Adh1 lineage.

Alcohol Dehydrogenase↗
PubMed1994

Hydroxymethyl-phytochelatins [(gamma-glutamylcysteine)n-serine] are metal-induced peptides of the Poaceae.

Exposure of several species of the family Poaceae to cadmium results in the formation of metal-induced peptides of the general structure (gamma-Glu-Cys)n-Ser (n=2-4). They are assumed to be formed from hydroxymethyl-glutathione (gamma-Glu-Cys-Ser) and are termed hydroxymethyl-phytochelatins (hm-PCs) in analogy to the homo-phytochelatins [(gamma-Glu-Cys)n-beta-Ala], discovered in legumes, and the phytochelatins [PCs, (gamma-Glu-Cys)n-Gly] found in most other plants and many fungi. The hm-PCs were isolated from the roots of cadmium-exposed rice (Oryza sativa L. cv Strella), and their structure was confirmed by amino acid analysis after total and enzymic hydrolysis and by tandem mass spectrometry. The hm-PCs probably play a significant role in heavy metal detoxication in rice. In addition to this new form of gamma-Glu-Cys (gamma EC) peptide, PCs and gamma EC peptides without C-terminal Ser or Gly are found. All gamma EC peptides are synthesized without delay after incubation of rice plants in 100 microM CdCl2 in the roots as well as in the shoots. Incubation times exceeding 24 h or higher concentrations of cadmium result in a selective enrichment of gamma EC peptides with higher chain length and an increased ratio of PCs to hm-PCs. gamma EC peptide synthesis is accompanied by a decrease of the glutathione content and an increase of the hydroxymethyl-glutathione content in roots and shoots of rice plants.

Amino Acid Sequence↗
PubMed2006

Multiple intercontinental dispersals shaped the distribution area of Hordeum (Poaceae).

The grass genus Hordeum (Poaceae, Triticeae), comprising 31 species distributed in temperate and dry regions of the world, was analysed to determine the relative contributions of vicariance and long-distance dispersal to the extant distribution pattern of the genus. Sequences from three nuclear regions (DMC1, EF-G and ITS) were combined and analysed phylogenetically for all diploid (20 species) and two tetraploid Hordeum species and the outgroup Psathyrostachys. Ages of clades within Hordeum were estimated using a penalized likelihood analysis of sequence divergence. The sequence data resulted in an almost fully resolved phylogenetic tree that allowed the reconstruction of intrageneric migration routes. Hordeum evolved c. 12 million years ago in South-west Asia and spread into Europe and Central Asia. The colonization of the New World and South Africa involved at least six intercontinental exchanges during the last 4 million years (twice Eurasia-North America, North America-South America, twice South America-North America and Europe-South Africa). Repeated long-distance dispersal between the northern and southern hemisphere were important colonization mechanisms in Hordeum.

Base Sequence↗