Differentially expressed proteins associated with drought tolerance in bananas (<Emphasis Type="Italic">Musa</Emphasis> spp.)

Bananas are one of the most important fruits in tropical and subtropical regions worldwide. Each year, banana plantations expand, but the areas available are mostly dry lands. The establishment of strategies for obtaining drought tolerant cultivars depends on understanding of biological responses at genetic, molecular and biochemical levels. Proteomics is a powerful tool for functional characterization of the response of plants to abiotic stress and little is known about drought tolerance in Musa spp. Therefore, the aim of this study was to identify proteins related to drought tolerance in two contrasting banana genotypes, Prata Anã and BRS Tropical, susceptible and tolerant to drought, respectively. Proteins were extracted from rhizomes of bananas grown under greenhouse conditions with control, irrigated and water deficit regimes. The differential protein expression pattern was established by two-dimensional (2-D) electrophoresis and spots analyzed in nano Q-Tof Micro UPLC. Twenty-three differentially expressed proteins were found in the tolerant genotype (BRS Tropical) under water deficit, with proteins involved in metabolism, defense and transport. Proteins were classified according to known function and biosynthetic pathways. Signaling proteins in response to water stress, especially for the biological function of growth and development of plants cells, were also encountered, whereas heat shock proteins played a significant role. This is the first report of proteomic analysis for drought tolerance in ‘Pome’ and ‘Silk-type’ bananas containing the ‘B’ genome. Our work provides insights into Musa spp. response to drought and data for further studies regarding molecular mechanisms, which determine how Musa spp. cells better overcome environmental perturbations.     

Detection of Pseudomonas savastanoi pv. savastanoi in Olive Plants by Enrichment and PCR

The sequence of the gene iaaL of Pseudomonas savastanoi EW2009 was used to design primers for PCR amplification. The iaaL-derived primers directed the amplification of a 454-bp fragment from genomic DNA isolated from 70 strains of P. savastanoi, whereas genomic DNA from 93 non-P. savastanoi isolates did not yield this amplified product. A previous bacterial enrichment in the semiselective liquid medium PVF-1 improved the PCR sensitivity level, allowing detection of 10 to 100 CFU/ml of plant extract. P. savastanoi was detected by the developed enrichment-PCR method in knots from different varieties of inoculated and naturally infected olive trees. Moreover, P. savastanoi was detected in symptomless stem tissues from naturally infected olive plants. This enrichment-PCR method is more sensitive and less cumbersome than the conventional isolation methods for detection of P. savastanoi.     

Effect of a virus associated with the reproductive system of the parasitoid wasp,Campoletis sonorensis,on host weight gain

The particulate fraction of the calyx fluid of the endoparasitoid, Campoletis sonorensis, reduces host weight gain when manually injected into healthy Heliothis virescens larvae. Reduced weight gain of the host, H. virescens, is normally associated with parasitism by C. sonorensis. Electron microscopy has confirmed that the particulate fraction of the calyx fluid is composed of virus particles and it appears that this virus, injected with the egg at oviposition, actually reduces host weight gain. The effect of the virus is negated when the calyx fluid is exposed to ultraviolet light prior to injection. Furthermore, the calyx fluid is effective only if injected into hosts; there is no effect on host weight gain when hosts are fed or topically treated with the virus-containing calyx fluid.     

Helianthus tuberosus agglutinin directly induces neutrophil migration, which can be modulated/inhibited by resident mast cells.

We investigated the effect of Helianthus tuberosus agglutinin (HTA) on neutrophil migration in vivo and in vitro. The role of resident cells in this effect was analyzed. Peritonitis was induced by injecting stimuli into rat (150-200 g) peritoneal cavities, and in vitro neutrophil chemotaxis was performed using a Boyden microchamber. HTA (80, 200, or 500 microg/mL per cavity) induced significant in vivo neutrophil migration (p < 0.05); in vitro assays showed that this lectin also induced neutrophil chemotaxis, an effect inhibited by the incubation of lectin associated with alpha-D(+)-mannose, its specific binding sugar. Depletion of the resident-cell population by peritoneal lavage did not alter HTA-induced neutrophil migration (200 microg/mL per cavity). The opposite strategy, increasing peritoneal macrophages by intraperitoneally injecting rats with thioglycollate, did not enhance the neutrophil migration produced by HTA (200 microg/mL per cavity). In addition, injection of supernatant from HTA-stimulated macrophage culture (300 microg/mL) into rat peritoneal cavities did not induce neutrophil migration. However, reduction of the peritoneal mast-cell population potentiated the neutrophil migration (p < 0.05) induced by HTA (200 microg/mL per cavity). Lectin from H. tuberosus has a direct neutrophil chemotatic effect that is modulated by mast cells.     

Study of the effect of the peptide loading and solvent system in SPPS by HRMAS-NMR.

The SPPS methodology has continuously been investigated as a valuable model to monitor the solvation properties of polymeric materials. In this connection, the present work applied HRMAS-NMR spectroscopy to examine the dynamics of an aggregating peptide sequence attached to a resin core with varying peptide loading (up to 80%) and solvent system. Low and high substituted BHAR were used for assembling the VQAAIDYING sequence and some of its minor fragments. The HRMAS-NMR results were in agreement with the swelling of each resin, i.e. there was an improved resolution of resonance peaks in the better solvated conditions. Moreover, the peptide loading and the attached peptide sequence also affected the spectra. Strong peptide chain aggregation was observed mainly in highly peptide loaded resins when solvated in CDCl3. Conversely, due to the better swelling of these highly loaded resins in DMSO, improved NMR spectra were acquired in this polar aprotic solvent, thus enabling the detection of relevant sequence-dependent conformational alterations. The more prominent aggregation was displayed by the VQAAIDYING segment and not by any of its intermediary fragments and these findings were also corroborated by EPR studies of these peptide-resins labelled properly with an amino acid-type spin probe.     

Pressure dependence of side chain <Superscript>13</Superscript>C chemical shifts in model peptides Ac-Gly-Gly-Xxx-Ala-NH<Subscript>2</Subscript>

For evaluating the pressure responses of folded as well as intrinsically unfolded proteins detectable by NMR spectroscopy the availability of data from well-defined model systems is indispensable. In this work we report the pressure dependence of ¹³C chemical shifts of the side chain atoms in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH₂ (Xxx, one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of a number of nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The size of the polynomial pressure coefficients B ₁ and B ₂ is dependent on the type of atom and amino acid studied. For H^N, N and C^α the first order pressure coefficient B ₁ is also correlated to the chemical shift at atmospheric pressure. The first and second order pressure coefficients of a given type of carbon atom show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure also are weakly correlated. The downfield shifts of the methyl resonances suggest that gauche conformers of the side chains are not preferred with pressure. The valine and leucine methyl groups in the model peptides were assigned using stereospecifically ¹³C enriched amino acids with the pro-R carbons downfield shifted relative to the pro-S carbons.     

Characterization of resistance to the bean weevil <Emphasis Type="Italic">Acanthoscelides obtectus</Emphasis> Say, 1831 (Coleoptera: Bruchidae) in common bean genotypes

The bean weevil Acanthoscelides obtectus (Say, 1831) (Coleoptera: Bruchidae) is one of the most serious pests of stored beans worldwide because of the damage it causes to grains within warehouses. The use of resistant genotypes may offer a control strategy for this pest. In the current study, we screened common bean genotypes of Andean American and Mesoamerican origin in laboratory and greenhouse bioassays to select the most promising beans for resistance to the bean weevil. In the laboratory, we evaluated number of eggs, period of development (egg-adult), number of emerged adults, dry weight of adults, and weight of consumed grains. In the greenhouse, number of pods per plant and number of grains per pod were evaluated. We also assessed the percentages of damaged pods per plant and damaged grains per pod. Combining the results obtained in the laboratory and greenhouse assays, the common bean genotypes Arc.1, Arc.2, Arc.1S, Arc.5S, and Arc.3S were identified as resistance expressing antibiosis against A. obtectus. The lowest percentages of damaged pods were found in the Arc.1 and Arc.1S genotypes, and their resistance to damage was apparently morphological (antixenotic) because they possessed structures that prevented contact between larvae and grains. The use of resistant genotypes in combination with other techniques may improve management of the weevil. Additionally, the resistant genotypes identified here can be used in breeding programs to develop common bean lines with resistance to A. obtectus.