Quantitative trait loci and underlying candidate genes controlling agronomical and fruit quality traits in octoploid strawberry <Emphasis Type="Italic">(Fragaria</Emphasis> × <Emphasis Type="Italic">ananassa</Emphasis>)

Breeding for fruit quality traits in strawberry (Fragaria × ananassa, 2n = 8x = 56) is complex due to the polygenic nature of these traits and the octoploid constitution of this species. In order to improve the efficiency of genotype selection, the identification of quantitative trait loci (QTL) and associated molecular markers will constitute a valuable tool for breeding programs. However, the implementation of these markers in breeding programs depends upon the complexity and stability of QTLs across different environments. In this work, the genetic control of 17 agronomical and fruit quality traits was investigated in strawberry using a F₁ population derived from an intraspecific cross between two contrasting selection lines, ‘232’ and ‘1392’. QTL analyses were performed over three successive years based on the separate parental linkage maps and a pseudo-testcross strategy. The integrated strawberry genetic map consists of 338 molecular markers covering 37 linkage groups, thus exceeding the 28 chromosomes. 33 QTLs were identified for 14 of the 17 studied traits and approximately 37% of them were stable over time. For each trait, 1–5 QTLs were identified with individual effects ranging between 9.2 and 30.5% of the phenotypic variation, indicating that all analysed traits are complex and quantitatively inherited. Many QTLs controlling correlated traits were co-located in homoeology group V, indicating linkage or pleiotropic effects of loci. Candidate genes for several QTLs controlling yield, anthocyanins, firmness and l-ascorbic acid are proposed based on both their co-localization and predicted function. We also report conserved QTLs among strawberry and other Rosaceae based on their syntenic location.     

Plant Conservation in the Caribbean Island Biodiversity Hotspot

While the Caribbean is a recognized “biodiversity hotspot”, plant conservation has not received adequate attention; particularly, given the high levels of endemism in many plant groups. Besides establishing protected areas, there needs to be a sustained effort to study the taxonomy, systematics and ecology of the flora. Recent phylogenetic studies have shown high levels of endemism and conservation studies indicate a large propotion of the flora is threatened with extinction. Eight recommendations are given for plant conservation in the region.     

Inhibition of Fas expression by RNAi modulates 5-fluorouracil-induced apoptosis in HCT116 cells expressing wild-type p53

Drug resistance to 5-fluorouracil (5-FU) is still a major limitation to its clinical use. In addition, the clinical value of p53 as a predictive marker for 5-FU-based chemotherapy remains a matter of debate. Here, we used HCT116 human colorectal cancer cells expressing wild-type p53 and investigated whether inhibition of Fas expression by interference RNA modulates 5-FU-induced apoptosis. Cells were treated with 5-FU (1, 4 or 8 microM) for 8-48 h. Cell viability was evaluated by trypan blue dye exclusion. Apoptosis was assessed by changes in nuclear morphology and caspase activity. The interference RNA technology was used to silence Fas expression. Caspase activation, p53, Fas, cytochrome c, and Bcl-2 family protein expression was evaluated by immunoblotting. 5-FU was cytotoxic in HCT116 cells (p<0.001). Nuclear fragmentation and caspase-3, -8 and -9 activities were also markedly increased in HCT116 cells after 5-FU (p<0.001). In addition, wild-type p53 and Fas expression were 25- and 4-fold increased (p<0.05). Notably, when interference RNA was used to inhibit Fas, 5-FU-mediated nuclear fragmentation and caspase activity were markedly reduced in HCT116 cells. Finally, western blot analysis of mitochondrial extracts from HCT116 cells exposed to 5-FU showed a 6-fold increase in Bax, together with a 3-fold decrease in cytochrome c (p<0.001). In conclusion, 5-FU exerts its cytotoxic effects, in part, through a p53/Fas-dependent apoptotic pathway that involves Bax translocation and mitochondrial permeabilization.     

Erratum to: Development of SCAR markers for rapid and specific detection of Pseudomonas syringae pv. morsprunorum races 1 and 2, using conventional and real-time PCR

Applied Microbiology and Biotechnology -     

The antimicrobial effects of glucosinolates and their respective enzymatic hydrolysis products on bacteria isolated from the human intestinal tract

Aims:  The aim of the study was to evaluate the in vitro antibacterial activity of glucosinolates and their enzymatic hydrolysis product against bacteria isolated from the human intestinal tract.
Methods and results:  Using a disc diffusion bioassay, different doses of intact glucosinolates and their corresponding hydrolysis products were tested. There were clear structure–activity and concentration differences with respect to the in vitro growth inhibition effects as well as differences in the sensitivities of the individual bacteria. The most effective glucosinolate hydrolysis products were the isothiocyanates; sulforaphane and benzyl isothiocyanate were the best inhibitors of growth. Indole-3-carbinol had some inhibitory effects against the Gram-positive bacteria but had no effect, even at the highest dose, against the Gram-negative bacteria. Indole-3-acetonitrile had some inhibitory activity against the Gram-negative bacteria. Glucosinolates, nitriles and amines were ineffective at all the doses used.
Conclusions:  Glucosinolate hydrolysis products and specifically the isothiocyanates SFN and BITC have significant antimicrobial activity against Gram-positive and Gram-negative bacteria, and might be useful in controlling human pathogens through the diet.
Significance and Impact of the Study:  This the first major in vitro study demonstrating the potential of these natural dietary chemicals as an alternative to, or in combination with, current antibiotic-based therapies for treating infectious diseases.     

In vivo transport of folded EGFP by the DeltapH/TAT-dependent pathway in chloroplasts of Arabidopsis thaliana

Among the protein translocation pathways of the thylakoid membrane in chloroplasts, the DeltapH/TAT pathway is unique in several aspects. In vitro transport assays with isolated chloroplasts or thylakoids have defined the trans-thylakoidal proton gradient as the sole requirement for effecting transport. From these studies, evidence has also accumulated indicating that, in contrast to the remaining protein transport pathways present in the thylakoid membrane, the DeltapH/TAT pathway is able to mediate the transport of folded proteins. The present work has established a novel approach to demonstrate the transport of folded proteins by this pathway in vivo. For this purpose, Arabidopsis thaliana plants were stably transformed with gene constructs expressing enhanced green fluorescent protein (EGFP) alone or fused to the transit peptides of different chloroplast proteins under the control of the 35S CAMV promoter. The intracellular and intraorganellar distribution of EGFP in the resulting transformants showed that while all the chloroplast transit peptides efficiently mediated the transport of EGFP into plastids, only those specific for the DeltapH/TAT pathway were able to direct the protein into the thylakoid lumen as well. This could be demonstrated both by fluorescence and immunoelectron microscopy. Analysis of isolated and fractionated chloroplasts using western blot and spectrofluorometric assays confirmed the presence of folded EGFP solely within the thylakoid lumen of these lines. These results strongly suggest that the protein adopts a folded state in the chloroplast stroma and thus, can only be translocated further into the chloroplast lumen by the DeltapH/TAT pathway.     

Life history of Amblyseius herbicolus (Chant) (Acari: Phytoseiidae) on coffee plants

The predaceous mite Amblyseius herbicolus (Chant) is the second most abundant phytoseiid on coffee plants (Coffea arabica L), after Euseius alatus DeLeon, in Lavras, MG, Brazil, associated to the vector of the coffee ring spot virus, Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae). Its life history was studied taking into account biological aspects, life table, predatory activity and functional and numerical responses in relation to the density of the prey. The adult female has longevity of 38 days when supplied with B. phoenicis. The intrinsic rate of population increase (r m) was 0.150 and the mean generation time (T) 25.3 days. The population doubles every 4.6 days. Thirty mites B. phoenicis /3-cm diameter coffee leaf arenas were separately offered to one specimen of each predator phase. Adult females were more efficient in killing all developmental phases of B. phoenicis, followed by the nymph stages. For the functional and numerical responses studies, from 0.14 to 42.3 immature specimens of the prey /cm(2) of arena were submitted to the predator, the preferred phase for predation. Predation and the oviposition of A. herbicolus increased with increasing prey density, with a positive and highly significant correlation. Regression analysis suggests a functional type II response, with a maximum daily predation near 35 B. phoenicis /cm(2) /one adult female.     

Entamoeba histolytica: ADP-ribosylation of secreted glyceraldehyde-3-phosphate dehydrogenase

In addition to its classic glycolytic role, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been implicated in many activities unrelated to glycolysis, such as membrane fusion, binding to host proteins and signal transduction. GAPDH can be the target of several modifications that allow incorporation to membranes and possible regulation of its activity; among these modifications is mono-ADP-ribosylation. This post-translational modification is important for the regulation of many cellular processes and is the mechanism of action of several bacterial toxins. In a previous study, we observed the extracellular ADP-ribosylation of a 37-kDa ameba protein. We report here that GAPDH and cysteine synthase A are the main ADP-ribosylated proteins in Entamoeba histolytica extracellular medium, GAPDH is secreted from ameba at 37 degrees C in a time-dependent manner, and its enzymatic activity is not inhibited by ADP-ribosylation. Extracellular GAPDH from ameba may play an important role in the survival of this human pathogen or in interaction with host molecules, as occurs in other organisms.     

Characteristics of loci and individuals are associated with germline microsatellite mutation rates in lesser kestrels (Falco naumanni)

Although microsatellites are one of the most popular tools in genetic studies, their mutational dynamics and evolution remain unclear. Here, we apply extensive pedigree genotyping to identify and analyze the patterns and factors associated with de novo germline mutations across nine microsatellite loci in a wild population of lesser kestrels (Falco naumanni). A total of 10 germline mutations events were unambiguously identified in four loci, yielding an average mutation rate of 2.96x10(-3). Across loci, mutation rate was positively correlated with locus variability and average allele size. Mutations were primarily compatible with a stepwise mutation model, although not exclusively involved single-step changes. Unexpectedly, we found an excess of maternally transmitted mutations (male-to-female ratio of 0.1). One of the analyzed loci (Fn2.14) resulted hypermutable (mutation rate=0.87%). This locus showed a size-dependent mutation bias, with longer alleles displaying deletions or additions of a small number of repeat than shorter alleles. Mutation probability at Fn2.14 was higher for females and increased with parental (maternal) age but was not associated with individual physical condition, multilocus heterozygosity, allele length or allele span. Overall, our results do not support the male-biased mutation rate described in other organisms and suggest that mutation dynamics at microsatellite loci are a complex process which requires further research.