Molecular phylogeny and systematics of Genista (Leguminosae) and related genera based on nucleotide sequences of nrDNA (ITS region) and cpDNA (trnL-trnF intergenic spacer)

Phylogenetic relationships of Genista and related genera (Teline, Chamaespartium, Pterospartum, Echinospartum, Ulex, Stauracanthus and Retama) were assessed by the analysis of sequences of the nrDNA internal transcribed spacer (ITS region), and the cpDNA trnL-trnF intergenic spacer. The tree obtained by combining both sets of data indicates the existence of three lines of diversification within Genista, that correspond to three subgenera: Genista, Phyllobotrys and Spartocarpus, however, each of these lineages encompass also species of the related genera Echinospartum, Teline, Retama, Chamaespartium, Pterospartum, Ulex, Stauracanthus. The molecular data do not support division of these subgenera into taxonomical units at the sectional level; only sections Genista and Spartocarpus are monophyletic groups. The sequences of both regions are also informative at the specific level, grouping morphologically related species (e.g. the G. cinerea aggregate). The molecular data have also helped to clarify the position of taxa whose relationships were not well established (e.g. G. valdes-bermejoi). The relationships of related genera that belong to the Genista lines of diversification have also been investigated. Echinospartum splits into two separate clades matching the separation of two ecological and caryological differentiated groups. Teline also forms two groups, both placed near to Genista subgenus Genista, but that separated from the main core of the group. Retama, morphologically well differentiated from Genista, is close to Genista subgenus Spartocarpus. Chamaespartium and Pterospartum do not form a monophyletic group. Chamaespartium is closer to Genista subgenus Genista, whereas Pterospartum stands close to: 1) Genista subgenus Spartocarpus (particularly, sect. Cephalospartum); and 2) the Ulex-Stauracanthus clade (a terminal derivative of Genista subgenus Spartocarpus). Cases of incongruence (e.g. Echinospartum, Chamaespartium, Teline) between the trees obtained from the two molecular markers, may be indicating hybridisation and/or introgression between different lines of Genisteae.     

Molecular approach to the phylogeny and systematics of Cytisus (Leguminosae) and related genera based on nucleotide sequences of nrDNA (ITS region) and cpDNA (trnL-trnF intergenic spacer)

 Phylogenetic relationships of Cytisus and allied genera (Argyrocytisus, Calicotome, Chamaecytisus, Cytisophyllum, and Spartocytisus) were assessed by analysis of sequences of the nrDNA internal transcribed spacer (ITS) and the cpDNA trnL-trnF intergenic spacer. Genera of the Genista-group (Chamaespartium, Echinospartum, Genista, Pterospartum, Spartium, Teline and Ulex) were included to check the position of Cytisus species transferred to Teline. The tree obtained by combining both sets of data indicates that the Genista and Cytisus groups form two separate clades. Cytisus heterochrous and C. tribracteolatus are more closely related to the Cytisus-group, thus their transfer to Teline is not supported by molecular data. Cytisus fontanesii (syn. Chronanthos biflorus) groups with Cytisophyllum sessilifolium and Cytisus heterochrous within the Cytisus-group. Similarly, Argyrocytisus battandieri falls within the Cytisus-group as a well differentiated taxon. All these taxa seem to have early diverged from the Cytisus-group. Their taxonomic rank should be reconsidered to better reflect their phylogenetic separation from Cytisus. On the contrary, Chamaecytisus proliferus and Spartocytisus supranubius enter in the main core of Cytisus, and they should better be included in sections of Cytisus (sect. Tubocytisus and Oreosparton, respectively). Sect. Spartopsis is not monophyletic and the position of several species, currently included in this section, deserves reevaluation: C. arboreus aggregate is closely related to C. villosus (sect. Cytisus) and to Calicotome; C. striatus is closely related to Cytisus sect. Alburnoides; and the position of C. commutatus (incl. C. ingramii) remains unclear. The relationships and positioning of several minor taxa (C. transiens, C. megalanthus, and C. maurus) are also discussed. Received November 22, 2001; accepted March 16, 2002 Published online: October 14, 2002 Addresses of the authors: Paloma Cubas (e-mail: cubas@farm.ucm.es) and Cristina Pardo (e-mail: cpardo@farm.ucm.es), Departamento de Biología Vegetal II, Facultad de Farmacia, Universidad Complutense, E-28040 Madrid, Spain. Hikmat Tahiri Faculté des Sciences, Université Mohammed V, BP 1014 Rabat, Morocco (e-mail: tahiri@ fsr.ac.ma).     

Exploring the protein–protein interaction landscape in plants

Protein–protein interactions (PPIs) represent an essential aspect of plant systems biology. Identification of key protein players and their interaction networks provide crucial insights into the regulation of plant developmental processes and into interactions of plants with their environment. Despite the great advance in the methods for the discovery and validation of PPIs, still several challenges remain. First, the PPI networks are usually highly dynamic, and the in vivo interactions are often transient and difficult to detect. Therefore, the properties of the PPIs under study need to be considered to select the most suitable technique, because each has its own advantages and limitations. Second, besides knowledge on the interacting partners of a protein of interest, characteristics of the interaction, such as the spatial or temporal dynamics, are highly important. Hence, multiple approaches have to be combined to obtain a comprehensive view on the PPI network present in a cell. Here, we present the progress in commonly used methods to detect and validate PPIs in plants with a special emphasis on the PPI features assessed in each approach and how they were or can be used for the study of plant interactions with their environment.     

Effects of solid-phase mass transfer on the performance of a stirred anaerobic sequencing batch reactor containing immobilized biomass

This work reports on experiments for an anaerobic sequencing batch reactor containing immobilized biomass which aimed at verifying the effects of solid-phase mass transfer on the reactor's overall performance. Four experiments were carried out at 30 degrees C with cubic polyurethane foam particles previously inoculated with anaerobic biomass. Different solid-phase mass transfer conditions were reached in each experiment by varying the size of the bioparticle from 0.5 to 3.0 cm. The reactor was fed with a low-strength synthetic wastewater containing protein, carbohydrates and lipid and the effects of mass transfer were evaluated through dynamic substrate concentration profiles during 8-hour batch cycles. A modified first-order kinetic model provided a good representation of the behavior of the dynamic concentration profiles. The solid-phase mass transfer was found to slightly affect the concentration of effluent organic matter expressed as chemical oxygen demand (COD). The concentration of residual effluent substrate increased as the size of the bioparticle was increased. The cycle time was not affected as the size of the bioparticle was increased from 0.5 to 2.0 cm. However, it was found that the cycle time in a reactor with 3.0-cm cubic particles should be higher than that required in systems with smaller particles. The apparent first-order kinetic parameter was estimated as 0.59+/-0.01 h(-1) for experiments with bioparticle sizes ranging from 0.5 to 2.0 cm, while a value of 0.48 h(-1) was obtained in the experiment with 3.0-cm bioparticles.     

Reduce, reuse, and recycle: developmental evolution of trait diversification

A major focus of evolutionary developmental (evo-devo) studies is to determine the genetic basis of variation in organismal form and function, both of which are fundamental to biological diversification. Pioneering work on metazoan and flowering plant systems has revealed conserved sets of genes that underlie the bauplan of organisms derived from a common ancestor. However, the extent to which variation in the developmental genetic toolkit mirrors variation at the phenotypic level is an active area of research. Here we explore evidence from the angiosperm evo-devo literature supporting the frugal use of genes and genetic pathways in the evolution of developmental patterning. In particular, these examples highlight the importance of genetic pleiotropy in different developmental modules, thus reducing the number of genes required in growth and development, and the reuse of particular genes in the parallel evolution of ecologically important traits.     

Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater

The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR - Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530 ± 37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller.