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Shared and novel molecular responses of mandarin to drought
No full textDrought is the most important stress experienced by citrus crops. A citrus cDNA microarray of about 6.000 genes has been utilized to identify transcriptomic responses of mandarin to water stress. As observed in other plant species challenged with drought stress, key genes for lysine catabolism, proline and raffinose synthesis, hydrogen peroxide reduction, vacuolar malate transport, RCI2 proteolipids and defence proteins such as osmotin, dehydrins and heat-shock proteins are induced in mandarin. Also, some aquaporin genes are repressed. The osmolyte raffinose could be detected in stressed roots while the dehydrin COR15 protein only accumulated in stressed leaves but not in roots. Novel drought responses in mandarin include the induction of genes encoding a new miraculin isoform, chloroplast beta-carotene hydroxylase, oleoyl desaturase, ribosomal protein RPS13A and protein kinase CTR1. These results suggest that drought tolerance in citrus may benefit from inhibition of proteolysis, activation of zeaxanthin and linolenoyl synthesis, reinforcement of ribosomal structure and down-regulation of the ethylene response
Predation by the mirids 'Nesidiocoris tenuis' and 'Macrolophus pygmaeus' on the tomato borer 'Tuta absoluta'
No full textRelevant Role of Fibronectin-Binding Proteins in Staphylococcus aureus Biofilm-Associated Foreign-Body Infections
No full textStaphylococcus aureus can establish chronic infections on implanted medical devices due to its capacity to form biofilms. Analysis of the factors that assemble cells into a biofilm has revealed the occurrence of strains that produce either a polysaccharide intercellular adhesin/poly-N-acetylglucosamine (PIA/PNAG) exopolysaccharide- or a protein-dependent biofilm. Examination of the influence of matrix nature on the biofilm capacities of embedded bacteria has remained elusive, because a natural strain that readily converts between a polysaccharide- and a protein-based biofilm has not been studied. Here, we have investigated the clinical methicillin (meticillin)-resistant Staphylococcus aureus strain 132, which is able to alternate between a proteinaceous and an exopolysaccharidic biofilm matrix, depending on environmental conditions. Systematic disruption of each member of the LPXTG surface protein family identified fibronectin-binding proteins (FnBPs) as components of a proteinaceous biofilm formed in Trypticase soy broth-glucose, whereas a PIA/PNAG-dependent biofilm was produced under osmotic stress conditions. The induction of FnBP levels due to a spontaneous agr deficiency present in strain 132 and the activation of a LexA-dependent SOS response or FnBP overexpression from a multicopy plasmid enhanced biofilm development, suggesting a direct relationship between the FnBP levels and the strength of the multicellular phenotype. Scanning electron microscopy revealed that cells growing in the FnBP-mediated biofilm formed highly dense aggregates without any detectable extracellular matrix, whereas cells in a PIA/PNAG-dependent biofilm were embedded in an abundant extracellular material. Finally, studies of the contribution of each type of biofilm matrix to subcutaneous catheter colonization revealed that an FnBP mutant displayed a significantly lower capacity to develop biofilm on implanted catheters than the isogenic PIA/PNAG-deficient mutant
Ensayo de injerto en alficoz ecológico
Get PDFEl alficoz (Cucumis melo var. Flexuosus) es un cultivo tradicional en la zona de
Elche y resulta de gran interés el estudio del injerto como método de lucha contra enfermedades
de suelo en cultivo ecológico.
El ensayo se desarrolló en la EEA de Elche, al aire libre, riego por goteo y 6 años
en ecológico. Como portainjerto se usó el RS-841 (Cucurbita híbrida) de Royal Sluis con
resistencias a Fusarium (FON), Verticilium y tolerancia a Phythium y nemátodos.
El diseño estadístico fue de 2 tratamientos (alficoz injertado y sin injertar) en 6
bloques al azar. Se controlaron las producciones 3 veces por semana, con un seguimiento
completo del estado fitosanitario del cultivo.
Analizadas estadísticamente las producciones encontramos diferencias significativas
(al 95%) entre los tratamientos, a favor del injerto, que llega a duplicar la producción
comercial del sin injertar (5,78 kg/m2 frente a 2,26 kg/m2). Las plantas sin injertar se vieron
afectadas en su práctica totalidad por el «colapso» del melón al mes de iniciarse las
recolecciones, mientras que las injertadas siguieron produciendo durante un mes más.
Se confirma el comportamiento del injerto como un eficaz método de prevención
frente a los patógenos del suelo en el cultivo del alficoz ecológico. Siendo aconsejable su
empleo incluso en aquellos casos en los que se presuma un buen estado fitosanitario del
suelo, ya que además produce un ligero incremento en la precocidad y vigor de la planta
Development of a CiFT Co-expression System for Functional Analysis of Genes in Citrus Flowers and Fruit
Get PDFWe have developed a CiFT co-expression system for the rapid evaluation of transgenic citrus flowers and fruit. In order to co-express a target gene and the CiFT gene, a CiFT co-expression vector was constructed by inserting the fragment containing a chimeric target gene into the binary vector harboring P35S::CiFT. This system was applied to metabolically engineer aroma components in trifoliate orange (Poncirus trifoliata L. Raf). In order to reduce the limonene level, a gene encoding limonene synthase (CitMTSE1) from satsuma mandarin (Citrus unshiu Marc.) was introduced into trifolliate orange in an anti-sense orientation with the CiFT co-expression vector. Transgenic plants flowered extremely early, and began to produce normal fruit within 2 years of Agrobacterium infection. Transcripts of transgenes were accumulated in reproductive tissues of transgenic plants, and endogenous transcripts for limonene synthase were reduced. The ratio of limonene to other monoterpenes was significantly decreased in flowers and fruit of transgenic plants. These results clearly indicated that the CiFT co-expression system is a useful tool for the functional analysis of genes in citrus flowers and fruit. Such analyses are important for several applications, including the metabolic engineering of aroma components in citrus
Graft Transmission Efficiencies and Multiplication of 'Candidatus Liberibacter americanus' and 'Ca. Liberibacter asiaticus' in Citrus Plants
No full textIn Brazil 'Candidatus Liberibacter asiaticus' and 'Ca. L. americanus' cause huanglongbing (also known as greening), the most destructive citrus disease. A shift in pathogen prevalence was observed over time, with a disproportional increase in 'Ca. L. asiaticus' occurrence. Graft transmission experiments were used for a comparative study of both species using budsticks from symptomatic branches of field-affected trees as inoculum. The plants were inoculated with 'Ca. L. asiaticus' or 'Ca. L. americanus' alone, or simultaneously with both species. Symptom manifestation and conventional and quantitative real-time polymerase chain reaction were used for plant evaluations. 'Ca. L. americanus' was detected mainly in symptomatic plants and 'Ca. L. asiaticus' was detected in symptomatic plants as well as in infected plants prior to symptom manifestation. Transmission percentages varied from 54.7 to 88.0% for 'Ca. L. asiaticus' and 10.0 to 45.2% for 'Ca. L. americanus' in two experiments. In co-inoculated plants, 12.9% contained 'Ca. L. americanus' only, 40.3% contained 'Ca. L. asiaticus' only, and 19.3% contained both species. Average bacterial titers for 'Ca. L. asiaticus' and 'Ca. L. americanus', in log cells per gram of leaf midrib, were 6.42 and 4.87 for the experimental plants and 6.67 and 5.74 for the field trees used as the source of inoculum. The higher bacterial populations of the 'Ca. L. asiaticus'-infected plants provided an explanation for the disproportional increase in field prevalence of this species over time, based on the greater likelihood for pathogen transmission by the insect vector
Are molecular tools solving the challenges posed by detection of plant pathogenic bacteria and viruses?
Get PDFPlant pathogenic bacteria, phytoplasmas, viruses and viroids are difficult to control, and preventive measures are essential to minimize the losses they cause each year in different crops. In this context, rapid and accurate methods for detection and diagnosis of these plant pathogens are required to apply treatments, undertake agronomic measures or proceed with eradication practices, particularly for quarantine pathogens. In recent years, there has been an exponential increase in the number of protocols based on nucleic-acid tools being those based on PCR or RT-PCR now routinely applied worldwide. Nucleic acid extraction is still necessary in many cases and in practice inhibition problems are decreasing the theoretical sensitivity of molecular detection. For these reasons, integrated protocols that include the use of molecular techniques as screening methods, followed by confirmation by other techniques supported by different biological principles are advisable. Overall, molecular techniques based on different types of PCR amplification and very especially on real-time PCR are leading to high throughput, faster and more accurate detection methods for the most severe plant pathogens, with important benefits for agriculture. Other technologies, such as isothermal amplification, microarrays, etc. have great potential, but their practical development in plant pathology is still underway. Despite these advances, there are some unsolved problems concerning the detection of many plant pathogens due to their low titre in the plants, their uneven distribution, the existence of latent infections and the lack of validated sampling protocols. Research based on genomic advances and innovative detection methods as well as better knowledge of the pathogens' lifecycle, will facilitate their early and accurate detection, thus improving the sanitary status of cultivated plants in the near future
Performance of Forner-Alcaide 5 and Forner-Alcaide 13, hybrids of Cleopatra mandarin x Poncirus trifoliata, as Salinity-Tolerant Citrus Rootstocks
No full textChloride and sodium concentrations and gas exchange parameters were measured on leaves of 'Valencia' orange scions grafted onto the rootstocks Cleopatra mandarin (CM), Poncirus trifoliato (PT) and their hybrids Forner-Alcaide 5 (FA-5) and Forner-Alcaide 13 (FA-13), grown in pots with different concentrations of NaCl in the external medium. Scions on CM accumulated less Cl(-) in their leaves than scions on PT. However, Na(+) concentrations were lower in scions on PT than on CM. Leaf Cl(-) exclusion appears to be transmitted to F1 hybrids FA-5 and FA-13. Also, the limited transport of Na(+) from rootstock to scions on PT was transmitted to FA-5. Leaf gas exchange parameters in salt-treated plants were reduced to different extents, depending on the rootstock. The decreases in net CO, assimilation and transpiration were more pronounced in CM, followed by PT and FA-13. The lowest reductions in both parameters occurred in scions on FA-5. The results indicate that, both in terms of saline ion exclusion and gas exchange parameters, FA-5 was the most tolerant genotype to salinity of the four studied, followed by FA-13
Plant Phenotype Demarcation Using Nontargeted LC-MS and GC-MS Metabolite Profiling
No full textThe characterization of the metabolome is a critical aspect in basic research and plant breeding. In this work, the Putative application of metabolomics for phenotyping closely related genotypes has been tested. Crude extracts were profiled by LC-MS and GC-MS, and mass data extraction was performed with XCMS software. Result validation was achieved with principal component analysis (PCA). The ability of the profiling methodologies to discriminate plant genotypes was assessed after hierarchical clustering analysis (HCA). Cluster robustness was assessed by a multiscale bootstrap resampling method. A better performance of LC-MS profiling over GC-MS was evidenced in terms of phenotype demarcation after PCA and HCA, Citrus demarcation was similarly achieved independently of the environmental conditions used to grow plants. In addition, when all different locations were pooled in a single experimental design, it was still possible to differentiate the three closely related genotypes. The presented methodology provides a fast and nontargeted workflow as a powerful tool to discriminate related plant phenotypes. The novelty of the technique relies on the use of mass signals as markers for phenotype demarcation independent of putative metabolite identities and the relatively simple analytical strategy that can be applicable to a wide range of plant matrices with no previous optimization
Killing niche competitors by remote-control bacteriophage induction
No full textA surprising example of interspecies competition is the production by certain bacteria of hydrogen peroxide at concentrations that are lethal for others. A case in point is the displacement of Staphylococcus aureus by Streptococcus pneumoniae in the nasopharynx, which is of considerable clinical significance. How it is accomplished, however, has been a great mystery, because H2O2 is a very well known disinfectant whose lethality is largely due to the production of hyperoxides through the abiological Fenton reaction. In this report, we have solved the mystery by showing that H2O2 at the concentrations typically produced by pneumococci kills lysogenic but not nonlysogenic staphylococci by inducing the SOS response. The SOS response, a stress response to DNA damage, not only invokes DNA repair mechanisms but also induces resident prophages, and the resulting lysis is responsible for H2O2 lethality. Because the vast majority of S. aureus strains are lysogenic, the production of H2O2 is a very widely effective antistaphylococcal strategy. Pneumococci, however, which are also commonly lysogenic and undergo SOS induction in response to DNA-damaging agents such as mitomycin C, are not SOS-induced on exposure to H2O2. This is apparently because they are resistant to the DNA-damaging effects of the Fenton reaction. The production of an SOS-inducing signal to activate prophages in neighboring organisms is thus a rather unique competitive strategy, which we suggest may be in widespread use for bacterial interference. However, this strategy has as a by-product the release of active phage, which can potentially spread mobile genetic elements carrying virulence genes