Floral initiation and inflorescence architecture: a comparative view

BACKGROUND: A huge variety of plant forms can be found in nature. This is particularly noticeable for inflorescences, the region of the plant that contains the flowers. The architecture of the inflorescence depends on its branching pattern and on the relative position where flowers are formed. In model species such as Arabidopsis thaliana or Antirrhinum majus the key genes that regulate the initiation of flowers have been studied in detail and much is known about how they work. Studies being carried out in other species of higher plants indicate that the homologues of these genes are also key regulators of the development of their reproductive structures. Further, changes in these gene expression patterns and/or function play a crucial role in the generation of different plant architectures. SCOPE: In this review we aim to present a summarized view on what is known about floral initiation genes in different plants, particularly dicotyledonous species, and aim to emphasize their contribution to plant architecture.     

Functional and intracellular signaling differences associated with the Helicobacter pylori AlpAB adhesin from Western and East Asian strains

Following adhesion of Helicobacter pylori to gastric epithelial cells, intracellular signaling leads to cytokine production, which causes H. pylori-related gastric injury. Two adjacent homologous genes (alpA and alpB), which encode H. pylori outer membrane proteins, are thought to be associated with adhesion and cytokine induction. We co-cultured gastric epithelial cells with wild type H. pylori strains and their corresponding alpA/alpB-deleted mutants (DeltaalpAB). Results were confirmed by complementation. Flow cytometry confirmed that AlpAB was involved in cellular adhesion. Deletion of alpAB reduced interleukin (IL)-6 induction in gastric epithelial cells. Deletion of alpAB reduced IL-8 induction with East Asian but not with Western strains. All AlpAB-positive strains tested activated the extracellular signal-regulated kinase, c-Fos, and cAMP-responsive element-binding protein. Activation of the Jun-N-terminal kinase, c-Jun, and NF-kappaB was exclusive to AlpAB from East Asian strains. DeltaalpAB mutants poorly colonized the stomachs of C57BL/6 mice and were associated with lower mucosal levels of KC and IL-6. Our results suggest that AlpAB may induce gastric injury by mediating adherence to gastric epithelial cells and by modulating proinflammatory intracellular signaling cascades. Known geographical differences in H. pylori-related clinical outcomes may relate to differential effects of East Asian and Western types of AlpAB on NF-kappaB-related proinflammatory signaling pathways.     

High-altitude chronic hypoxia during gestation and after birth modifies cardiovascular responses in newborn sheep

Perinatal exposure to chronic hypoxia induces sustained pulmonary hypertension and structural and functional changes in both pulmonary and systemic vascular beds. The aim of this study was to analyze consequences of high-altitude chronic hypoxia during gestation and early after birth in pulmonary and femoral vascular responses in newborn sheep. Lowland (LLNB; 580 m) and highland (HLNB; 3,600 m) newborn lambs were cathetherized under general anesthesia and submitted to acute sustained or stepwise hypoxic episodes. Contractile and dilator responses of isolated pulmonary and femoral small arteries were analyzed in a wire myograph. Under basal conditions, HLNB had a higher pulmonary arterial pressure (PAP; 20.2 +/- 2.4 vs. 13.6 +/- 0.5 mmHg, P < 0.05) and cardiac output (342 +/- 23 vs. 279 +/- 13 ml x min(-1) x kg(-1), P < 0.05) compared with LLNB. In small pulmonary arteries, HLNB showed greater contractile capacity and higher sensitivity to nitric oxide. In small femoral arteries, HLNB had lower maximal contraction than LLNB with higher maximal response and sensitivity to noradrenaline and phenylephrine. In acute superimposed hypoxia, HLNB reached higher PAP and femoral vascular resistance than LLNB. Graded hypoxia showed that average PAP was always higher in HLNB compared with LLNB at any Po2. Newborn lambs from pregnancies at high altitude have stronger pulmonary vascular responses to acute hypoxia associated with higher arterial contractile status. In addition, systemic vascular response to acute hypoxia is increased in high-altitude newborns, associated with higher arterial adrenergic responses. These responses determined in intrauterine life and early after birth could be adaptive to chronic hypoxia in the Andean altiplano.     

Distribution, diversity and environmental adaptation of highland papayas (Vasconcellea spp.) in tropical and subtropical America

Vasconcellea species, often referred to as highland papayas, consist of a group of fruit species that are closely related to the common papaya (Carica papaya). The genus deserves special attention as a number of species show potential as raw material in the tropical fruit industry, fresh or in processed products, or as genetic resources in papaya breeding programs. Some species show a very restricted distribution and are included in the IUCN Red List. This study on Vasconcellea distribution and diversity compiled collection data from five Vasconcellea projects and retrieved data from 62 herbaria, resulting in a total of 1,553 georeferenced collection sites, in 16 countries, including all 21 currently known Vasconcellea species. Spatial analysis of species richness clearly shows that Ecuador, Colombia and Peru are areas of high Vasconcellea diversity. Combination of species occurrence data with climatic data delimitates the potential distribution of each species and allows the modeling of potential richness at continent level. Based on these modeled richness maps, Ecuador appears to be the country with the highest potential Vasconcellea diversity. Despite differences in sampling densities, its neighboring countries, Peru and Colombia, possess high modeled species richness as well. A combination of observed richness maps and modeled potential richness maps makes it possible to identify important collection gaps. A Principal Component Analysis (PCA) of climate data at the collection sites allows us to define climatic preferences and adaptability of the different Vasconcellea species and to compare them with those of the common papaya.     

Molecular evolution of PIII-SVMP and RGD disintegrin genes from the genus Crotalus

Several types of disintegrins have been isolated from Crotalus spp rattlesnakes, including RGD disintegrins, and PIII-SVMPs. We isolated six cDNAs from snake venom glands using RT-PCR. Three RGD disintegrins (atroxatin, mojastin, and viridistatin) and three PIII-SVMPs (catroriarin, scutiarin, and viristiarin) cDNAs were isolated from the rattlesnakes Crotalus atrox, Crotalus scutulatus scutulatus, and Crotalus viridis viridis, respectively. Atroxatin and Viridistatin shared 90% amino acid identity to each other, and 87% identity to Mojastin. Scutiarin and Viristiarin were identical. All PIII-SVMPs isolated in this study shared the highest amino acid identity with Catrocollastatin. cDNA and protein sequences for RGD disintegrins, one MVD disintegrin, and PIII-SVMPs of the genus Crotalus (present in the NCBI database), were used in phylogenetic analysis. Neighbor-joining analysis of PIII-SVMP and RGD/MVD disintegrin-coding DNA sequences showed that these groups of genes separate into separate clades. A Phi(ST) pairwise comparison and Analysis of Molecular Variance (AMOVA) between PIII-SVMPs and RGD/MVD disintegrins showed significant genetic differences. Mutations observed in ten of the cDNAs analyzed did not affect Cys-coding sequences. Our K(A)/K(S) data suggest that rapid evolution occurred between the genes coding for PIII-SVMPs resulting, in the production of RGD disintegrin-coding genes. However, once these genes diverged, mutations in the PIII-SVMP-coding genes were accumulated less frequently.     

The CK1 gene family: expression patterning in zebrafish development

Protein kinase CK1 is a ser/thr protein kinase family which has been identified in the cytosol cell fraction, associated with membranes as well as in the nucleus. Several isoforms of this gene family have been described in various organisms: CK1alpha, CK1beta, CK1delta, CK1epsilon and CK1gamma. Over the last decade, several members of this family have been involved in development processes related to wnt and sonic hedgehog signalling pathways. However, there is no detailed temporal information on the CK1 family in embryonic stages, even though orthologous genes have been described in several different vertebrate species. In this study, we describe for the first time the cloning and detailed expression pattern of five CK1 zebrafish genes. Sequence analysis revealed that zebrafish CK1 proteins are highly homologous to other vertebrate orthologues. Zebrafish CK1 genes are expressed throughout development in common and different territories. All the genes studied in development show maternal and zygotic expression with the exception of CK1epsilon. This last gene presents only a zygotic component of expression. In early stages of development CK1 genes are ubiquitously expressed with the exception of CK1epsilon. In later stages the five CK1 genes are expressed in the brain but not in the same way. This observation probably implicates the CK1 family genes in different and also in redundant functions. This is the first time that a detailed comparison of the expression of CK1 family genes is directly assessed in a vertebrate system throughout development.