Downregulation of the Basic Peroxidase Isoenzyme from Zinnia elegans by Gibberellic Acid

Hypocotyl formation during the epigeal germination of seedlings is under strict hormonal regulation. In a 3 d old Zinnia elegans seedling system, gibberellic acid (GA_3) exerts an opposite effect to that exerted by light on hypocotyl photomorphogenesis because GA_3 promotes an etiolated-like growth with an inhibition of radial (secondary) growth. For this reason, the effect of GA_3 on the basic peroxidase isoenzyme from Z. Elegans (ZePrx), an enzyme involved in hypocotyl lignin biosynthesis, was studied. The results showed that GA_3 reduces ZePrx activity, similarly to the way in which it reduces seedling secondary growth. This hormonal response is supported by the analysis of the ZePrx promoter, which contains four types of GA_3-responsive cis-elements: the W Box/O2S; the Pyr Box; the GARE; and the Amy Box. Taken together, these results suggest that ZePrx is directly regulated by GA_3, with this effect matching the inhibitory effect of GA on the hypocotyl secondary growth.     

Hepatic myofibroblasts: A heterogeneous population of multifunctional cells in liver fibrogenesis

Hepatic myofibroblasts constitute a heterogenous population of highly proliferative, pro-fibrogenic, pro-inflammatory, pro-angiogenic and contractile cells that sustain liver fibrogenesis and then fibrotic progression of chronic liver diseases of different aetiology to the common advanced-stage of cirrhosis. These α-smooth muscle actin-positive myofibroblast-like cells, according to current literature, mainly originate by a process of activation and trans-differentiation that involves either hepatic stellate cells or fibroblasts of portal areas. Hepatic myofibroblasts can also originate from bone marrow-derived cells, including mesenchymal stem cells or circulating fibrocytes able to engraft chronically injured liver, as well as, in certain conditions, by a process of epithelial to mesenchymal transition involving hepatocytes and cholangiocytes. Hepatic myofibroblasts may have also additional crucial roles in modulating immune response and in the cross talk with hepatic progenitor (stem) cells as well as with malignant cells of either primary hepatocellular carcinomas or of metastatic cancers.     

Geospatial analysis of spatiotemporal patterns of pH, total suspended sediment and chlorophyll-a on the Amazon floodplain

We applied spatial data analysis and geostatistical procedures to pH, total suspended sediment and chlorophyll-a concentration data gathered on an Amazon floodplain lake. Variographic analysis and ordinary kriging interpolation were used to identify and describe spatiotemporal patterns of variability in these parameters, which are relevant to understand the dynamics of water circulation on the floodplain lake. In spite of the complexity of the processes underlying the spatiotemporal patterns, this approach demonstrated that the heterogeneity in the seasonal water composition is forced not only by the Amazon River flood pulse, but also by the lake bottom topography and the wind intensity.     

Evaluation of the presence of aspartic proteases from Centaurea calcitrapa during seed germination

Aspartic proteinases are present in a variety of organisms including plants. Common features of aspartic proteases include an active site cleft that contains two catalytic aspartic residues, acid pH optima for enzymatic activity, inhibition by pepstatin A. Plant aspartic proteinases occur in seeds and may be involved in the processing of storage proteins. Many of them have been purified and characterized. The presence of aspartic proteases in seeds of Centaurea calcitrapa during germination was investigated by measuring the activity on enzyme extracts. The aspartic proteases are present mainly in the beginning of seed germination suggesting that they could initiate the degradation of protein reserves in germinating seeds.

These proteases were purified by salt precipitation followed by anion-exchange chromatography. Purified aspartic proteases have an optimal pH between 3.5 and 4.5, using FTC-hemoglobin as substrate and an optimal temperature at 52 °C. The ability of seed extracts for milk clotting was tested and the clotting time that was achieved is in the same range found for flower extracts appropriated for special cheeses in which weak clotting agents are required.     

Gene expression modulation by chalcopyrite and bornite in Acidithiobacillus ferrooxidans

Acidithiobacillus ferrooxidans is a mesophilic, acidophilic, chemolithoautotrophic bacterium that obtains energy from the oxidation of ferrous iron (Fe²⁺), elemental sulfur and reduced sulfur compounds. The industrial interest in A. ferrooxidans resides in its capacity to oxidize insoluble metal sulfides into soluble metal sulfates, thus allowing the recovery of the desired metals from low-grade sulfide ores. In the present work, RNA arbitrarily primed PCR (RAP-PCR) was performed to identify cDNAs differentially expressed in A. ferrooxidans cells grown in the presence of Fe²⁺ and cells maintained for 24 h in the presence of the copper sulfides bornite and chalcopyrite. Eighteen cDNAs corresponding to genes with known function were identified, and their relative expression was further characterized by real-time quantitative PCR. Bornite had a mild effect on the expression of the 18 genes analyzed. None of these genes was down-regulated and among the few genes up-regulated, it is worth mentioning lepA and def-2 that are involved in protein synthesis. Chalcopyrite presented the most significant changes. Five genes related to protein processing were down-regulated, and another 5 genes related to the transport system were up-regulated. The up- and down-regulation of these genes in the presence of bornite and chalcopyrite could be due to alterations in the ideal pH, presence of copper ions in solution and nutrient limitation. The results suggest that gene expression modulation might be important for the A. ferrooxidans early response to copper sulfides.     

Floral polymorphism in Chamaecrista flexuosa (Fabaceae-Caesalpinioideae): a possible case of atypical enantiostyly?

Background and Aims

Reciprocal herkogamy, including enantiostyly and heterostyly, involves reciprocity in the relative positions of the sexual elements within the flower. Such systems result in morphologically and, since pollen is deposited on and captured from different parts of the pollinator, functionally distinct floral forms. Deviations from the basic pattern may modify the functionality of these mechanisms. For heterostylous species, such deviations are generally related to environmental disturbances, pollination services and/or reduced numbers of one floral morph. Deviations for enantiostylous species have not yet been reported. This study aims to investigate enantiostyly in Chamaecrista flexuosa, in particular the presence of deviations from the standard form, in an area of coastal vegetation in north-east Brazil.

Methods

Observations and investigations of floral biology, the reproductive system, pollinator behaviour, floral morphology and morphometry were performed.

Key Results

In C. flexuosa flowers, anthers of different size but similar function are grouped. The flowers were self-compatible and set fruits after every treatment, except in the spontaneous self-pollination experiment, thereby indicating their dependence on pollen vectors. The flowers were pollinated by bees, especially Xylocopa cearensis and X. grisencens. Pollen is deposited and captured from the ventral portion of the pollinator''s body. Variations in the spatial arrangement of floral elements allowed for the identification of floral morphs based on both morphological and functional criteria. Using morphological criteria, morphologically right (MR) and morphologically left (ML) floral morphs were identified. Three floral morphs were identified using functional criteria: functionally right (FR), functionally central (FC) and functionally left (FL). Combinations of morphologically and functionally defined morphs did not occur in equal proportions. There was a reduced frequency of the MR–FR combination.

Conclusions

The results indicate the occurrence of an atypical enantiostyly in C. flexuosa. This seems to improve reproductive success by increasing the efficiency of pollen deposition and capture.     

Enantiostyly in Chamaecrista ramosa (Fabaceae‐Caesalpinioideae): floral morphology,pollen transfer dynamics and breeding system

Enantiostyly is a form of reciprocal herkogamy, in which floral morphs present reciprocal differences in the position of sexual elements, and occurs in monomorphic and dimorphic forms. This polymorphism maximises cross‐pollination and reduces self‐pollination, being very common within the subtribe Cassiinae (Fabaceae). Nevertheless, few studies have investigated the functionality of enantiostyly, particularly in this plant group. The present study aimed to investigate enantiostyly and its functionality in Chamaecrista ramosa, a monomorphic enantiostylous shrub, in an area of coastal vegetation in northeast Brazil. Pollen deposition and capture on the body of floral visitors, the relationship of these data with floral biology and breeding system, and morph ratio were evaluated. Pollen deposition and capture occurred in specific sites of the floral visitor body, showing the functionality of enantiostyly. The floral architecture, associated with the floral visitor behaviour, resulted in indirect pollen deposition on the floral visitor body. This occurred through a loop made by the pollen upon the inner petal surface, similar that generally reported for other Cassiinae. Chamaecrista ramosa is self‐compatible, although no fruit set was observed through spontaneous self‐pollination. The occurrence and number of floral morphs was similar within clumps. Enantiostyly seems to be advantageous for this species, as it results in efficient pollen capture and deposition, reduces the chances of autogamy and maximises intermorph pollen flow.