Ultrastructural changes during early infection of Vigna unguiculata and Phaseolus vulgaris leaves by Xanthomonas axonopodis pv. phaseoli and an unexpected association between chloroplast and mitochondrion

Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli, is an important disease affecting beans causing considerable yield losses in many producing areas. Our aim was to investigate Xap–beans interactions in the first 48 h after infection analyzing structurally relevant changes by electron microscopy. Scanning electron microscopy analysis demonstrated morphological changes on leaf surfaces of both species. Transmission electron microscopy showed different types of chloroplast structural disorganization in both parenchyma and bundle sheath cells of Vigna unguiculata which were only observed in parenchyma cells of Phaseolus vulgaris. Additionally, we report an unexpected physical association between the chloroplasts and mitochondria observed only to P. vulgaris-infected plants.     

Identification and partial characterization of two cysteine proteases from castor bean leaves (<Emphasis Type="Italic">Ricinus communis</Emphasis> L.) activated by wounding and methyl jasmonate stress

Jasmonates are signaling molecules that play key roles in wound response and regulate the biosynthesis of many defensive proteins, including proteases. In this study, we investigate the effects of wounding and methyl jasmonate (MJ) application on the protein expression pattern of Ricinus communis L. leaves and on proteolytic activity. Gelatin zymography demonstrated that both MJ and mechanical wounding induce alterations in the proteolytic pattern of castor bean leaves (R. communis L.). Expression of two cysteine proteases (38 and 29 kDa) was induced by the treatments employed; however, MJ induced a higher protease level than mechanical wounding during the stress period (24, 48, and 72 h). The increase in protease activity mirrors the decline in soluble protein content and rubisco degradation that may indicate initiation of senescence in castor plants. The 29 kDa protease has an acidic optimal pH; whereas the 38 kDa protease has a neutral optimum activity. Both proteases were almost completely inhibited by E-64 and cystatin. The significant induction of these proteins by MJ suggests a possible role of cysteine proteases in leaf senescence as well as their involvement in regulating both the wound response and MJ in castor bean plants.     

Intra and interannual variability in the Madeira River water chemistry and sediment load

Concentrations of cations (Na⁺, Ca²⁺, Mg²⁺, K⁺, NH₄ ⁺), anions (HCO₃ ^?, Cl^?,?NO₃ ^?, SO₄ ^2?, PO₄ ^3?) and suspended sediments in the Madeira River water were?determined near the city of Porto Velho (RO), in order to assess variation in?water chemistry from 2004 to 2007. Calcium and bicarbonate were the dominant?cation and anion, respectively. Significant seasonal differences were found,?with highest concentrations occurring during the dry season, as expected from?the drainage of Andean carbonate-rich substratum. Interannual variations were?also observed, but became significant only when annual average discharge was?25% less than normal. Under this atypical discharge condition, bicarbonate was?replaced by sulfate, and higher suspended sediment concentrations and loads?were also observed. Compared to previously published studies, it appears that?no significant changes in water chemistry have occurred during the last 20?C30?years, although differences in approaches and sampling designs among this and previous studies may not allow detection of modest changes.?The calculated suspended sediment load reported here is close to the values presented elsewhere, reinforcing the relative importance of this river as a?sediment supplier for the Amazon Basin. Seasonality has a significant control?on the chemistry of Madeira River waters, and severe decrease in discharge due?to anthropogenic changes, such as construction of reservoirs or the occurrence?of drier years??a plausible consequence of global climate change??may lead?to modification in the chemical composition as well in the sediment deliver to?the Amazon River.     

Involvement of the AT1 receptor in the venoconstriction induced by angiotensin II in both the inferior vena cava and femoral vein

Although angiotensin II-induced venoconstriction has been demonstrated in the rat vena cava and femoral vein, the angiotensin II receptor subtypes (AT₁ or AT₂) that mediate this phenomenon have not been precisely characterized. Therefore, the present study aimed to characterize the pharmacological receptors involved in the angiotensin II-induced constriction of rat venae cavae and femoral veins, as well as the opposing effects exerted by locally produced prostanoids and NO upon induction of these vasomotor responses. The obtained results suggest that both AT₁ and AT₂ angiotensin II receptors are expressed in both veins. Angiotensin II concentration-response curves were shifted toward the right by losartan but not by PD 123319 in both the vena cava and femoral vein. Moreover, it was observed that both 10⁻⁵ M indomethacin and 10⁻⁴ M L-NAME improve the angiotensin II responses in the vena cava and femoral vein. In conclusion, in the rat vena cava and femoral vein, angiotensin II stimulates AT₁ but not AT₂ to induce venoconstriction, which is blunted by vasodilator prostanoids and NO.     

Relation between bacterial activity in the surface microlayer and estuarine hydrodynamics

Bacterial communities of the surface microlayer (SML) of the estuary Ria de Aveiro (Portugal) were characterized in terms of abundance and activity during a 2-year survey at two sites with distinct hydrodynamic properties (marine and brackish water zones). The hydrodynamic conditions were simulated using a bidimensional numerical model and related to the microbiological observations. The pattern of variation of bacterial biomass productivity (BBP) was distinct between the two sampling sites. At the outer site, BBP was significantly lower at the SML, whereas at the inner site, it was significantly enhanced at the SML. Although the total bacterial abundance was similar in the SML and underlying water (UW), the fraction of cells attached to particles was significantly higher at the SML (two to three times). The integration of microbiological results with environmental and hydrological variables shows that strong currents in the marine zone promote the vertical mixing, inhibiting the establishment of an SML bacterial community distinct from that of UW. In contrast, in the brackish water zone, lower current velocities provide conditions for enhancing the bacterial activity in the enriched SML. Estuarine dynamics influence the distribution and activity of microorganisms at the SML and in the water column, with anticipated impacts for the carbon cycle in the estuarine environment.     

Photosynthetic characteristics of ornamental passion flowers grown under different light intensities

Responses of leaf gas exchange, fluorescence emission, chlorophyll concentration, and morpho-anatomical features to changes in photosynthetic photon flux density (PPFD) were studied in three wild ornamental species of Passiflora L. to select sun and shade species for landscaping projects. Artificial shade was obtained with different shading nylon nets, under field conditions, which allowed the reduction of 25, 50, and 75% of global radiation, along with a control treatment under full sunlight. For Passiflora morifolia the highest mean values of light-saturated net photosynthetic rate (P _Nmax) and light compensation point (LCP) were observed at 50 and 25% shade, respectively, while the highest values of dark respiration rate (R _D) and apparent quantum yield (α) were observed at 75% shade. For Passiflora suberosa litoralis the highest value of P _max was observed at full sunlight. The highest mean values for P _max, R _D, and LCP for Passiflora palmeri var. sublanceolata were obtained at 25% shade. The highest values of net photosynthetic rate (P _N) for P. morifolia, P. palmeri var. sublanceolata, and P. suberosa litoralis were 21.09, 16.15, and 12.36 μmol(CO₂) m⁻² s⁻¹, observed at 50 and 75% shade and full sunlight, respectively. The values of the minimal chlorophyll fluorescence (F₀) were significantly different in P. suberosa litoralis and P. palmeri var. sublanceolata, increasing with the increase of the irradiance. In contrast, the values of maximum photochemical efficiency of PSII (F_v/F_m) were significantly different only in P. suberosa litoralis, being higher at 75%, progressively reducing with the increase of PPFD levels. The total concentration of chlorophyll (Chl) was higher in shaded plants than in the ones cultivated in full sunlight. On the other hand, the values of Chl a/b ratio were reduced in shaded plants. A significant effect of shade levels on leaf area (LA) and specific leaf area (SLA) was found for the three species, whose highest mean values were observed at 75% shade. The thickness of foliar tissues was significantly higher for the three species at full sunlight and 25% shade. These results suggested that P. morifolia and P. palmeri var. sublanceolata appeared to be adapted to moderate shade conditions. P. suberosa litoralis presented higher plasticity to greater variation of the irradiance levels, while the photoinhibition was one of the limiting factors for this species at full sunlight.     

Minimal concentration of human IgM and IgG antibodies necessary to protect mice from challenges with live O6 Escherichia coli

This work evaluated the ability of human anti-lipopolysaccharide O6 IgM and IgG antibodies to protect mice challenged with Escherichia coli serotype O6 : K2ac. Purified IgM-effluent, purified IgG, pools of normal human serum (NHS), or control group were injected into mice 18 h before challenges with O6 E. coli. Interleukin 6 and tumor necrosis factor alpha were quantified in the sera of test and control groups. All mice receiving purified IgM-effluent (66.6 mg L(-1) of anti-lipopolysaccharide O6 IgM antibodies) and NHS survived. Purified IgG (1.1 mg L(-1) of anti-lipopolysaccharide O6 IgG antibodies) protected 87.5% of the animals. The control group showed no protective ability. The minimal concentration of anti-lipopolysaccharide O6 IgM antibodies, able to protect 50% of the animals was 33.3 mg L(-1) of purified IgM-effluent, whereas purified IgG was able to protect 50% of the animals with only 1.1 mg L(-1) of anti-lipopolysaccharide O6 IgG antibodies. Serum from animals pretreated with purified IgM-effluent and purified IgG before challenges with lipopolysaccharide O6 did not have detectable pro-inflammatory cytokines. Hepatocytes of the control group were completely invaded by bacteria, whereas none was found in animals pretreated with purified IgM-effluent and purified IgG. Higher concentrations of anti-lipopolysaccharide O6 IgM antibodies as compared to anti-lipopolysaccharide O6 IgG antibodies were needed to protect mice from challenges with E. coli O6 serotype.     

Infection Process of Cercospora coffeicola on Coffee Leaf

Brown eye spot, caused by Cercospora coffeicola, is an important disease of coffee. Both adaxial and abaxial leaf surfaces were inoculated with a conidial suspension of C. coffeicola. Samples were collected from 4 to 168 h after inoculation and then again at 35 days. Germinated conidia showed positive tropism to stomata where attempted penetrations occurred. Appressoria were not observed. After penetration, C. coffeicola colonized the lacunous parenchyma both inter and intracellularly. Sporulation occurred through or around the stomata. Results from this study provide new insights into the infection process of C. coffeicola on coffee leaf.     

Current strategies for osteochondral regeneration: from stem cells to pre-clinical approaches

Damaged cartilage tissue has no functional replacement alternatives and current therapies for bone injury treatment are far from being the ideal solutions emphasizing an urgent need for alternative therapeutic approaches for osteochondral (OC) regeneration. The tissue engineering field provides new possibilities for therapeutics and regeneration in rheumatology and orthopaedics, holding the potential for improving the quality of life of millions of patients by exploring new strategies towards the development of biological substitutes to maintain, repair and improve OC tissue function. Numerous studies have focused on the development of distinct tissue engineering strategies that could result in promising solutions for this delicate interface. In order to outperform currently used methods, novel tissue engineering approaches propose, for example, the design of multi-layered scaffolds, the use of stem cells, bioreactors or the combination of clinical techniques.