Pollination and seed dispersal of Melocactus ernestii Vaupel subsp. ernestii (Cactaceae) by lizards: an example of double mutualism

Recent studies show that the mutualistic role of lizards as pollinators and seed dispersers has been underestimated, with several ecological factors promoting such plant–animal interactions, especially on oceanic islands. Our aim is to provide a quantitative assessment of pollination and seed dispersal mutualisms with lizards in continental xeric habitats. We carried out focal observations of natural populations of Melocactus ernestii (Cactaceae) in the Caatinga, a Brazilian semiarid ecosystem, in order to record the frequency of visits, kind of resource searched and behaviour of visiting animals towards flowers and/or fruits. We made a new record of the lizard Tropidurus semitaeniatus foraging on flowers and fruits of M. ernestii. During the search for nectar, T. semitaeniatus contacted the reproductive structures of the flowers and transported pollen attached to its snout. Nectar production started at 14:00 h, with an average volume of 24.4 μl and an average concentration of solutes of 33%. Approximately 80% of the seeds of M. ernestii found in the faeces of T. semitaeniatus germinated under natural conditions. The roles of T. semitaeniatus as pollinator and seed disperser for M. ernestii show a clear relationship of double mutualism between two endemic species, which may result from the environmental conditions to which both species are subject. Seasonality, low water availability and arthropod supply in the environment, high local lizard densities, continuous nectar production by the flower and fruits with juicy pulp may be influencing the visits and, consequently, pollination and seed dispersal by lizards in this cactus.     

Dynamics of CRISPR Loci in Microevolutionary Process of Yersinia pestis Strains

The potential use of CRISPR loci genotyping to elucidate population dynamics and microevolution of 146 Yersinia pestis strains from different biovars and locations was investigated in this work. The majority of strains from the Orientalis biovar presented specific spacer arrays, allowing for the establishment of a CRISPR signature for their respective isolates. Twenty-one new spacers were found in the Y. pestis strains from plague foci in Brazil. Ninety-three (64%) strains were grouped in the G1 genotype, whereas the others were distributed in 35 genotypes. This study allowed observing a microevolutionary process in a group of Y. pestis isolated from Brazil. We also identified specific genotypes of Y. pestis that were important for the establishment of the bacteria in plague foci in Brazil. The data have provided supporting evidence for the diversity and dynamics of CRISPR loci present in the genome of Y. pestis strains from plague foci in Brazil.     

Concanavalin-A induces IL-17 production during the course of Candida albicans infection

In a previous study, our group verified that 100% of mice survived to a lethal dose of Candida albicans following pretreatment with concanavalin-A (Con-A) for 3 days. This work proposed to investigate whether treatment could mediate an adaptative immune response involving T(H) 17 cells. A significant increase in IL-17 levels at 6 h postinfection was observed and was maintained up to 18 h in the Con-A group, whereas in control mice, a reduction in this cytokine was verified. In addition, T(H) 17 cells develop in the presence of TGF-β, IL-1 β, and IL-6 that were increased significantly 2 h postinfection in Con-A-treated mice. Macrophages were involved in the process, engulfing greater numbers of yeast cells, and were activated through TNF-α and interferon-γ produced at significant levels at 2 h postinfection. A significant increase in IL-12 levels was also observed at 2 h postinfection. Thus, activated macrophages were probably more capable of killing and processing Candida antigens, signalizing an adaptative immune response. Macrophages from controls did not prevent yeast-to-hyphae transition and were partially destroyed, as shown in scanning microscopy. These results suggest that treatment with Con-A facilitated the triggering of T(H) 17 and T(H) 1 responses via IL-17 and IFN-γ production, leading to the resolution of C. albicans infection.     

<Emphasis Type="Italic">Xanthomonas gardneri</Emphasis> exoenzymatic activity towards plant tissue

Bacterial spot caused by Xanthomonas spp. is an important tomato and pepper disease worldwide. Recent outbreaks of bacterial spot disease in Central Brazil and Canada have been attributed to Xanthomonas gardneri, which is also recognized as group D of Xanthomonas campestris pv. vesicatoria. Carotenoid-like pigments called xanthomonadins, which are diagnostic for yellow Xanthomonas spp., were extracted from X. gardneri. It was shown that the model plant Arabidopsis thaliana, member of the Brassicaceae family, can develop disease symptoms in response to different isolates of X. gardneri. Secretion of enzymes has been shown to play an important role in pathogenicity for different pathogens, and to begin to understand the interaction of X. gardneri and A. thaliana, a biochemical analysis of secreted proteins in the presence of A. thaliana leaves was performed. Different enzymatic activities such as for cellulase, α-arabinofuranosidase, pectinase, invertase and xylanase were assayed. In the presence of leaves, cellulase activity was highest after 60 and 72 h of growth and α-arabinofuranosidase activity was detected between 12 and 72 h of growth. Pectinase, invertase and xylanase activities were not detected. Cellulase and α-arabinofuranosidase activities may be important for X. gardneri acquisition of plant nutrients through degradation of cellulose fibers and hemicellulose of the cell wall, respectively, to the invasion of the host tissue and/or may generate signal molecules that are recognized by the plant. This is the first study to address how X. gardneri responds to host plant tissue.     

Histological study of somatic embryogenesis induction on zygotic embryos of macaw palm (<Emphasis Type="Italic">Acrocomia aculeata</Emphasis> (Jacq.) Lodd. ex Martius)

The aim of this paper was to describe the histological events that led to somatic embryogenesis in macaw palm (Acrocomia aculeata (Jacq.) Lodd. ex Martius). Zygotic embryos were inoculated on Y₃ medium containing 9 μM 4-amino-3,5,6-trichloropicolonic acid (picloram). Somatic embryos regenerated from nodular callus on induction medium with activated charcoal under photoperiod or without activated charcoal under dark. Many proembryos originated from the fundamental meristem after 10–20 days of culture. When transferred to medium containing activated charcoal, under photoperiod, calli regenerated into somatic embryos of unicellular origin. These embryos had protoderm, plumule and procambial strands and some of them could germinate. After 30–40 days of culture, meristematic masses grew from procambial cells. The masses generated nodular callus, and after transfer to medium without activated charcoal, under dark, they generated somatic embryos of multicellular origin. Those embryos did not regenerate into plants.     

Pathology of Exfoliated Oropharyngeal Epithelial Cells Infected with Wild-Type Adenovirus

Adenovirus disease was diagnosed in 2 hr by staining exfoliated infected oropharyngeal cells with fluorescein-tagged rabbit antisera to adenovirus types 4 and 7. The method was as sensitive as the standard virus isolation procedures, but serological cross reactions were observed. Viral antigens were detected in both the nucleus and cytoplasm of infected cells. Infection was accompanied by the outpouring of large numbers of polymorphonuclear leukocytes and smaller numbers of mononuclear cells. The method provides a model for the study of the cellular response to viral upper respiratory disease.     

Role of nitric oxide on quality of freshly ejaculated bull spermatozoa during heparin-induced in vitro capacitation

The objective of this study was to assess the effects of nitric oxide (NO) on heparin-induced capacitation in vitro of fresh bull sperm, through the addition of Nω-nitro-l-arginine methyl ester (L-NAME, a NO-synthesis inhibitor) and l-arginine (L-Arg, a NO-synthesis precursor) to the capacitation medium. In Experiment 1, different concentrations of L-NAME (0.1, 1, 10 mM) and of L-Arg (10 mM) were added to the capacitation medium. Sperm motility and vigor were subjectively appraised using direct light microscopy; sperm membrane integrity was examined using a 2% Trypan blue solution while the concentration of nitrate/nitrite (NO₃⁻/NO₂⁻) was determined by using the Griess method over a 5 h capacitation period. The addition of 10 mM L-NAME has inhibited NO synthesis, sperm progressive motility, sperm vigor and sperm membrane integrity (P < 0.05) as compared to control. The addition of 10 mM L-Arg to the capacitation medium increased all variables evaluated in comparison to the control (P < 0.05). In Experiment 2, mitochondrial activity was assessed through the MTT test (3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), and sperm capacitation was assessed through the test of penetration in homologous oocytes after addition of the 10 mM L-NAME, and of the 10 mM L-Arg. The addition of 10 mM L-NAME caused mitochondrial activity (40%) and the percentage of oocytes penetrated (77%) to decrease in relation to the control (P < 0.05). After addition of 0.6 mM L-Arg + 10 mM L-NAME, partial reversal of mitochondrial activity did occur (only 20%). The addition of 10 mM L-Arg increased the percentage of oocytes penetrated as compared to control (21%) (P < 0.05). These results indicate that: (1) NO is involved in control of progressive sperm motility, vigor, membrane integrity, and mitochondrial activity along the period of heparin-induced capacitation of fresh bovine sperm via NOS/NO; (2) adequate L-Arg/NO concentrations into the capacitation medium can potentiate heparin action or act independently for increasing the number or the quality of capacitated sperm.