Phenylpropanoids from Paspalum atratum (Poaceae)

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Different patterns of aerenchyma formation in two hygrophytic species of Paspalum (Poaceae) as response to flooding

Paspalum modestum and P. wrightii are perennial grasses growing in permanent and seasonally flooded areas, respectively. The former produces short rhizomes and floating culms, the latter forms long rhizomes and erect culms. Variations in percentage aerenchymatous space (PAS) in different organs as a response to flooding was analysed using a clone of each species. Eighteen plantlets of each clone were cultivated during 7 months under flooded vs. unflooded conditions. After this period, roots, rhizomes, culms, and leaf sheaths were collected and prepared. PAS was measured using an image analysis device, and data were analysed using ANOVA.Production of aerenchyma took place in both species within the cortical parenchyma of roots, rhizomes and culms, and the mesophyll of leaf sheaths, both in flooded and unflooded plants. Under flooding conditions PAS increased in both species, although the individual response of organs differed: whereas in P. modestum PAS increased primarily in substratum-fixed roots, in P. wrightii all organs produced additional aerenchyma uniformly. Contrasting responses are understood as adaptations to permanent and seasonal flooding, respectively.     

Microsatellite loci for Paspalum atratum (Poaceae) and cross-amplification in other species

? Premise of the study: Paspalum atratum is a perennial, cespitose, tropical grass native to Central and South America. This species belongs to a polyploid complex (Plicatula group) little known at the genetic level. The characterized microsatellite markers provide new informative tools for further studies of the hybridization, mating systems, and structure of the population. ? Methods and Results: Using the microsatellite-enriched library method, we isolated and characterized 19 microsatellite markers from P. atratum. Eleven of them were polymorphic, showing a variable degree of variation, while eight were monomorphic in the samples analyzed. Additionally, the transferability of these microsatellite markers was tested in other species. ? Conclusions: These results suggest that the characterized markers have enough discriminatory potential to be used in genetic characterizations of Paspalum taxa, which are based on an understanding of their mating systems and genetic structure, as well as in understanding the evolutionary processes involved in the evolution of groups of Paspalum.     

Unusual chromosome numbers in Paspalum L. (Poaceae: Paniceae) from Brazil

Somatic chromosome numbers were determined for 20 new germplasm accessions of Paspalum, belonging to 17 species collected in Brazil. Chromosome number is reported for the first time for P. reduncum (2n = 18), P. cinerascens (2n = 20), P. cordatum (2n = 20), P. filgueirasii (2n = 24), P. ammodes (2n = 36), P. bicilium (2n = 40), P. heterotrichon (2n = 40), and P. burmanii (2n = 48). New cytotypes were confirmed for two germplasm accessions of P. carinatum (2n = 30) and P. trachycoleon (2n = 36), one of P. clavuliferum (2n = 40) and one of P. lanciflorum (2n = 40), indicating variability in these species. The remaining chromosome numbers reported here confirm previous counts. The unexpected chromosome numbers 2n = 18, 24, 36, and 48 in Paspalum species, which are usually shown to be multiples of 10, suggest that much more collection and cytogenetic characterization are necessary to assess the whole chromosomal and genomic multiplicity present in the genus, which seems to be much more diverse than currently thought to be.     

Evolutionary implications of substitution patterns in prolamin genes of Oryza glaberrima (African rice, Poaceae) and related species

Patterns of sequence variation of nuclear genes encoding 10-kDa and 16-kDa prolamin seed storage proteins were examined in Oryza glaberrima (African rice, Poaceae) and O. barthii and compared to available sequences for the genus to assess potential application of these gene families in evolutionary studies. Sequence variation among species in 10-kDa genes was very low. In contrast, the 16-kDa genes have undergone rapid evolution, displaying a larger number of length and point mutations that in some cases result in frame shift or produce truncated protein or pseudogenes. The proportion of nonsynonymous substitution is high in both genes. Although nonsynonymous mutations did not alter the overall profile of the protein, pronounced shifts in proportions of some amino acids were evident and could have systematic application. The data provide support for a proposed direct evolution of the Asian (O. sativa) and African rice from O. rufipogon and O. barthii, respectively. Patterns of amino acid frequencies of the 10-kDa genes show the distinctness of O. rufipogon and O. longistaminata from the other species. The study underscores the potential application of the prolamin genes as markers from the nuclear genome for evolutionary studies in grasses at different taxonomic levels.     

A phylogenetic analysis of the genus Paspalum (Poaceae) based on cpDNA and morphology

With about 350 species, Paspalum is one of the richest genera within the Poaceae. Its species inhabit ecologically diverse areas along the Americas and they are largely responsible for the biodiversity of grassland ecosystems in South America. Despite its size and relevance, no phylogeny of the genus as a whole is currently available and infrageneric relationships remain uncertain. Many Paspalum species consist of sexual-diploid and apomictic-polyploid cytotypes, and several have arisen through hybridization. In this paper we explore the phylogenetic structure of Paspalum using sequence data of four non-coding cpDNA fragments from a wide array of species which were combined with morphological data for a subset of diploid taxa. Our results confirmed the general monophyly of Paspalum if P. inaequivalve is excluded and the small genus Thrasyopsis is included. Only one of the four currently recognized subgenera was monophyletic but nested within the remainder of the genus. Some informal morphological groups were found to be polyphyletic. The placement of known allopolyploid groups is generally congruent with previously stated hypotheses although some species with shared genomic formulae formed paraphyletic arrangements. Other species formed a basal grade including mostly umbrophilous or hygrophilous species. It is hypothesized that the genus may have diversified as a consequence of the expansion of C4 grass-dominated grasslands in South America.     

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.     

Intergeneric hybridization and C-banding patterns inHordelymus (Triticeae,Poaceae)

Crosses ofHordelymus europaeus (2n = 4x = 28) with four genera in theTriticeae were attempted. Adult hybrids were obtained in combinations withHordeum bogdanii (2x),Hordeum depressum (4x), andSecale cereale (2x). The meiotic pairing was very low in the hybrids withH. bogdanii andSecale cereale (0.12 and 0.30 chiasmata/cell, respectively), whereas high pairing (9.90 chiasmata/cell) was found in hybrids withH. depressum due to autosyndetic pairing ofH. depressum chromosomes. The chromosome complement ofHordelymus europaeus comprised 16 metacentrics, 8 submetacentrics, and 4 SAT-chromosomes. The Giemsa C-banding patterns of the chromosomes were characterized by small to minute bands at no preferential positions. It is hypothesized thatHordelymus europaeus may genomically be closest related toTaeniatherum andPsathyrostachys spp.     

丛枝菌根真菌对百喜草的生理特性的影响

采用盆栽法研究了丛枝菌根（AM）真菌摩西球囊霉（Glomus mosseae）对水分胁迫条件下百喜草（Paspalum notatum）生长、渗透调节及抗氧化酶的影响。结果表明：接种AM真菌显著提高了百喜草的株高、地上部与根部鲜重、地上部P、K、Mn及根部P、Ca、Mn含量,明显降低了地上部Zn及根部Fe、B、Cu水平;随着干旱程度的加深,接种株的地上部相对含水量及叶绿素含量相对稳定且均显著高于未接种株,接种株地上部相对电导率、MDA含量均显著低于未接种株,接种株的地上部POD活性与脯氨酸含量均显著增加且均显著高于未接种株,AM侵染对SOD活性的影响较小。可见,接种AM真菌Glomusmossecte提高了植株体内保护酶活性（如POD）及渗透调节能力（如脯氨酸、P、K、Ca等渗透调节物含量的增加）,从而显著增强了百喜草的抗旱性。     

东喜马拉雅地区雀稗属一新种

西藏雀稗 新种 图1Paspalum xizangenseB. S. Sun et H. Sun sp. nov. Figure 1Species P. vaginato Sw. affinis, sed culmis caespitosis erectis vel ascendentibus, lematibus inferoribus sparsim villosis deffert.Caespitose perennial. Culms 20-40 cm, erect or ascending. Sheaths glabrous, ligule about 0.5 mm; blades 3-10 cm long, 3-6 mm wide, glabrous. Inflorescence of 2-3 racemes arranged digitately,raceme 3-6 cm, glabrous, with narrowly singed rhachis. Spikelets 2-2.3 mm, solitary, seesile, in 2-ro…     

Evaluation of meiotic abnormalities and pollen viability in aposporous and sexual tetraploid Paspalum notatum (Poaceae)

We analyzed anaphase I configurations and pollen viability in aposporous and sexual tetraploid (2n?=?4x?=?40) cytotypes of Paspalum notatum. Five natural aposporous accessions and three experimentally obtained sexual individuals were used. In addition, 16 (8 aposporous and 8 sexual) F₁ hybrids, previously classified by their mode of reproduction, were analyzed. Cytogenetic observations revealed normal and abnormal anaphase I configurations in both aposporous and sexual genotypes. Anaphase I abnormalities were mainly laggard chromosomes, chromatin bridges, and micronuclei. On average, 44.36?% of aposporous meiocytes and 29.66?% of sexual ones showed abnormal anaphase I configurations. The total numbers of normal and abnormal anaphase I were highly significantly different between aposporous and sexual strains. The pollen viability test indicated that aposporous individuals had significantly more non-viable pollen than sexual ones; a positive correlation (r?=?0.71; r ²?=?0.50) between the variables was detected. Analysis of aposporous and sexual hybrids confirmed differences in the numbers of normal and abnormal anaphase I patterns in the aposporous and sexual parents. However, similar proportions of viable pollen were produced by both groups of hybrids. In this case, the variables were not correlated (r?=?0.23; r ²?=?0.05). Data from this study indicated that aposporous strains had a genetic rearrangement affecting meiosis that was absent in the experimentally obtained sexual individuals and that it was transmitted to the progeny. The possible association between meiotic abnormalities and the inheritance of apospory is discussed.     

Novelties in the Festuca valesiaca group (Poaceae) from the central Alps

Due to their ploidy levels, their morphological and anatomical characters and their distribution the central alpine Festuca stricta subsp. bauzanina (2n = 8x = 56) and Festuca ovina var. guinochetii (2n = 10x = 70), both belonging to the Festuca valesiaca group, are raised to the specific level. As a new subspecies Festuca bauzanina subsp. rhaetica is described here. The taxa of the polyploid Festuca valesiaca group are morphologically, anatomically and chorologically characterised and an identification key for these taxa in the central Alps is presented.     

Differential gene expression patterns in the autogamous plant Hordeum euclaston (Poaceae)

Sib-seedlings of 95 strains of the strictly autogamous grass Hordeum euclaston were analyzed by horizontal polyacrylamide gel electrophoresis for four isoenzyme systems at a specific ontogenetic stage. We found differences in the activity of some genes among individuals of this species. Hence, an ontogenetic analysis was carried out to investigate 12 strains at five ontogenetic stages, to determine the patterns of expression of these genes during development. The differences in the presence versus absence of certain isoenzyme bands may be due to differential regulatory activation in response to environmental differences, as all plants showed the same structural genes, although these genes were active in different tissues and/or times of development. These results indicate the importance of differential gene activation in the metabolic phenotype variability of this strictly autogamous, highly homozygous species. The same structural alleles for isoenzymes showed the active form of the enzymes (phenotypic expression) to be present in different tissues and/or stages of development. Differential isoenzyme gene activation was shown to be directly responsible for the enzymatic variability (metabolic phenotype) presented by the plants, which seem to possess almost no heterozygosis.     

A taxonomic study of theCalamagrostis tashiroi group (Poaceae)

TheCalamagrostis tashiroi group was taxonomically revised by examination of population samples from four areas and herbarium specimens. Results of the morphological examination, coupled with observations of the habitats, showed that three taxa with distinct morphological features and definite geographical ranges can be recognized in this group. They were disposed asCalamagrostis tashiroi subsp.tashiroi, C. tashiroi subsp.sikokiana, stat. nov. andC. onibitoana, sp. nov.     

Evolutionary dynamics of Waxy and the origin of hexaploid Spartina species (Poaceae)

We investigated the evolutionary dynamics of duplicated copies of the granule-bound starch synthase I gene (GBSSI or Waxy) within polyploid Spartina species. Molecular cloning, sequencing, and phylogenetic analyses revealed incongruences between the expected species phylogeny and the inferred gene trees. Some genes within species were more divergent than expected from ploidy level alone, suggesting the existence of paralogous sets of Waxy loci in Spartina. Phylogenetic analyses indicate that this paralogy originated from a duplication that occurred prior to the divergence of Spartina from other Chloridoideae. Gene tree topologies revealed three divergent homoeologous sequences in the hexaploid S. alterniflora that are consistent with the proposal of an allopolyploid origin of the hexaploid clade. Waxy sequences differ in insertion–deletion events in introns, which may be used to diagnose gene copies. Both paralogous and homoeologous coding regions appear to evolving under selective constraints.     

Evolutionary divergence of AP-PCR (RAPD) patterns

Rates at which AP-PCR patterns diverge among isolated taxa were examined to test whether they exhibit clocklike regularity. The results showed that rates of divergence differed significantly among the groups examined (primates, antelopes, and Hawaiian Drosophila grimshawi). Therefore, AP-PCR divergence rates cannot be used as a "universal clock" with an invariant rate in all animals. Nevertheless, within each group, a strong relationship existed between degree of AP-PCR pattern divergence and time since separation of isolated taxa. Thus, AP-PCR divergence may prove useful for dating evolutionary events if calibrated within a more limited taxon.      

Interspecific hybridizations in the Elymus semicostatus group (Poaceae).

Meiotic pairing in 16 interspecific hybrids in the genus Elymus is reported. The hybrids were made among seven species in the Elymus semicostatus group, viz., E. semicostatus, E. validus (subgroup I), E. abolinii (subgroup II), E. fedtschenkoi, E. nevskii, E. praeruptus (subgroup III), and E. panormitanus (subgroup IV). All species are tetraploid (2n = 4x = 28) and possess the SY genomes. Meiotic pairing was distinctly higher in hybrids made within subgroups than between subgroups, but the genomes in E. panormitanus have differentiated from those in the other species. These results generally support the subdivision of the E. semicostatus group based on morphological data but also indicate that the subgroups are more distantly related than previously believed, and that the group may be nonmonophyletic.