Restriction site variation in chloroplast DNA and nuclear ribosomal DNA was examined in 16 accessions from the Salicaceae comprising ten species of Populus and one outgroup species of Salix. Forty-nine restriction site mutations in the chloroplast DNAs were used to generate one most parsimonious phylogenetic tree. This tree indicates that all varieties of P. nigra (black poplars of sect. Aigeiros) have a chloroplast genome, maternally inherited, derived from the clade including the white poplars (P. alba and segregate species of sect. Populus) and divergent from the American cottonwoods of their own section. Twenty-one restriction site mutations in the nuclear ribosomal DNAs generated a single most parsimonious phylogenetic tree that indicates that the nucleargenome ofP. nigra is distinct from both the white poplars and American cottonwoods. The incongruity of these independent molecular phylogenies provides evidence for an unusual origin of the black poplars. Populus alba or its immediate ancestor acted as the maternal parent in a hybridization event with the paternal lineage of P. nigra. Subsequent backcrosses to the paternal species gave rise to the extant P. nigra with a chloroplast genome of P. alba and the nuclear genome of the paternal species. These hybridization and introgression events must have pre-dated the divergence of the black poplar varieties. The biphyletic nature of the P. nigra genomes suggests that dependency on one class of molecular or morphological markers or the merging of the two kinds of data sets to derive accurate estimates of true phylogenies could be misleading in plants.

Evolution of Populus nigra (sect. Aigeiros): introgressive hybridization and the chloroplast contribution of Populus alba (sect. Populus).

The microspore is at the centre of a variety of topics in modern plant science and breeding Isolated microspore cultures have the remarkable quality of resembling the alternation of generations in the life cycle of angiosperms, ie the change between the diploid sporophytec and the haploid gametophytec generation Although the natural destination of microspore development is to differentiate into mature pollen and accomplish fertilization, isolated and in vitro cultured microspores or young pollen grains can either differentiate into mature, fertile pollen (the male gametophytes) by culture in a rich medium without stress, or divide repeatedly and develop into embryos (sporophytes) after a stress treatment As experimental systems, microspore cultures are used to investigate pollen development and pollination, embryogenesis, totipotency, cytodifferentiation, cell cycle, phase change and the role of stress in development As a tool in genetic engineering, they can be used to produce doubled haploids (recombinant inbreds) for plant breeding and gene mapping, to overcome crossing barriers (male sterility and self-incompatibility), to induce and select for mutants and to create transgenic plants In this review genetic, cell biological and molecular aspects of in vitro microspore development are presented and put in the context of current basic and applied plant science

The microspore: A haploid multipurpose cell

Western Himalayan alpine pastures are among the most diverse ecological locations on the globe. Four alpine pastures were investigated to study species distribution patterns, richness, similarity, and community structure in Bagh District, Azad Kashmir, Pakistan. Four communities, Poa–Primula–Sibbaldia, Primula–Caltha–Primula, Poa alpina–Poa pratensis–Scirpus, and Sibbaldia–Poa–Scirpus, were identified on the basis of an importance value index. The average value of species richness was 1.42; Simpson's and Shannon–Wiener's diversity values were 3.13 and 0.91, respectively; the degree of maturity index was 44.1; and species evenness was 0.901. Local alpine flora was dominated by a hemicriptophytic life form with microphyllous leaf spectra. The species–environment correlation was analyzed using canonical correspondence analysis. A negative correlation of both diversity and richness was revealed with altitudinal gradient. Anthropogenic disturbances showed a significant negative impact on distribution ...

Species Diversity, Community Structure, and Distribution Patterns in Western Himalayan Alpine Pastures of Kashmir, Pakistan

1U.S. Forest Service, Northern Research Station, Institute for Applied Ecosystem Studies, 5985 Highway K, Rhinelander, WI 54501, USA 2ArborGen, LLC, P.O. Box 180438, Tallahassee, FL 32318, USA 3Iowa State University, Department of Natural Resource Ecology and Management, 339 Science II, Ames, IA 50011, USA 4Queen’s University, Geography Department, Mackintosh-Corry Hall, Room D108, Kingston, Ontario, Canada K7L 3N6 5University of Florida, School of Forest Resources and Conservation, 118 Newins-Ziegler Hall, Room 2, Bldg. 182, Gainesville, FL 32611, USA 6U.S. Forest Service, Southern Research Station, Center for Forest Disturbance Science, 320 Green Street, Athens, GA 30602, USA 7State University of New York, School of Environmental Science and Forestry, 346 Illick Hall, Syracuse, NY 13210, USA *Email: rzalesny@fs.fed.us, Phone: (715) 362-1132

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Woody biomass from short rotation energy crops.

The establishment of pollen-pistil compatibility is strictly regulated by factors derived from both male and female reproductive structures. Highly diverse small cysteine-rich proteins (CRPs) have been found to play multiple roles in plant reproduction, including the earliest stages of the pollen-stigma interaction. Secreted CRPs found in the pollen coat of members of the Brassicaceae, the pollen coat proteins (PCPs), are emerging as important signalling molecules that regulate the pollen-stigma interaction. Using a combination of protein characterization, expression and phylogenetic analyses we identified a novel class of Arabidopsis thaliana pollen-borne CRPs, the PCP-Bs (for pollen coat protein B-class) that are related to embryo surrounding factor (ESF1) developmental regulators. Single and multiple PCP-B mutant lines were utilized in bioassays to assess effects on pollen hydration, adhesion and pollen tube growth. Our results revealed that pollen hydration is severely impaired when multiple PCP-Bs are lost from the pollen coat. The hydration defect also resulted in reduced pollen adhesion and delayed pollen tube growth in all mutants studied. These results demonstrate that AtPCP-Bs are key regulators of the hydration 'checkpoint' in establishment of pollen-stigma compatibility. In addition, we propose that interspecies diversity of PCP-Bs may contribute to reproductive barriers in the Brassicaceae.

PCP‐B class pollen coat proteins are key regulators of the hydration checkpoint in Arabidopsis thaliana pollen–stigma interactions

Structural and cytochemical characteristics of stigmas of Populus alba (section Leuce) and P. nigra (section Aigeiros) have been studied to provide an understanding of the cell biology of the interspecific incompatibility reactions between these two species. In addition to specific morphological characteristics, stigma surfaces differ in the presence of an exudate studied by ultrastructural and stigma print techniques. P. nigra shows features of a dry-type stigma covered by a pellicle, whereas P. alba has a copious exudate typical of a wet-type stigma that contains unsaturated lipids.

Incompatibility in Populus: structural and cytochemical characteristics of the receptive stigmas of Populus alba and P. nigra.

s of poster presentations 44 P010 Antifungal agents induces alteration in the matrix composition of candida glabrata biofilms Rodrigues, Celia (Minho University, Departement of Biological Engineering Department, Braga ); Fonseca, Elza (Minho University, Departement of Biological Engineering Department, Braga , AUT); Goncalves, Bruna (Minho University, Departement of Biological Engineering Department, Braga ); Bogas, Diana (Minho University, Departement of Biological Engineering Department, Braga ); Silva, Sonia (Minho University, Departement of Biological Engineering Department, Braga ); Azeredo, Joana (Minho University, Departement of Biological Engineering Department, Braga ); Henriques, Mariana (Minho University, Departement of Biological Engineering Department, Braga ) Candida glabrata has emerged as the second most prevalent pathogen, after Candida albicans, in mucosal and invasive fungal infection. Its ability to form biofilms has been considered one of the most important virulence factors, since they present a high resistance to antifungal agents used in fungal infections treatment. Moreover, there is a lack of information about the physiological response of C. glabrata biofilms to antifungal agents. Thus, the aim of this study was to evaluate the effect of different antifungal agents on C. glabrata biofilm composition and the influence in related resistance genes expression. For that C. glabrata biofilms were formed in the presence of fluconazole (Flu), voriconazole (Vrz) and amphotericin B (AmB). Biofilm matrix composition was evaluated in terms of polysaccharides, proteins and ergosterol and ERG genes expression was also assessed. As expected C. glabrata biofilms are more resistant to Flu, Vrz and AmB than planktonic cells. . Although in a strain dependent manner, polysaccharides were increased in the presence of the antifungals, in opposition to proteins, which decreased in the presence of AmB and Vrz. Due to the interaction of these agents with ergosterol, even in different ways, we evaluated, for the first time, the presence of this compound in the extracelluar matrix. It was noticed that ergosterol was, in fact, present in all the matrices and in general it increased with the presence of the drugs. Therefore, there is an obvious answer of biofilm cells to the stress induced by the different agents, that caused and alteration of matrix composition. In order to determine if the increased concentration of ergosterol in the biofilm matrix was caused by an up-regulation of proteins responsible for ergosterol synthesis, ERG expression was evaluated.. Although ERG gene expression was very strain dependent is was possible to verify that some genes, as ERG11 and ERG6, were upregulated in biofilm cells. Interestingly one strain was unable to express ERG genes when grown in the presence of Vrz. It was then possible to conclude that biofilm cells upon exposure to antifungal agents overexpress ERG genes, which seems to contribute to an increase in ergosterol concentration in the biofilm matrix.

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M. Villar

Papers

Incompatibility in Populus: structural and cytochemical characteristics of the receptive stigmas of Populus alba and P. nigra.

Abstracts of Poster Presentations