Functional characterization of two banana NPR1 genes for pathogen defense response in Arabidopsis

The Non-expressor of pathogenesis-related1 gene (NPR1) mediates the induction of pathogenesis-related (PR) gene products, vital for resistance in plants. In this study, the role of two previously isolated Cavendish banana NPR1-like genes (MNPR1A and MNPR1B) has been characterized in protection against Xanthomonas campestris, Hylaperonospora arabidopsidis, Botrytis cinerea and Pseudomonas syringae pathogens. The specific aim was to investigate if sequence differences in both genes are responsible for differential activity against pathogens because in a previous expression study, MNPR1A and not MNPR1B had been more responsive to the banana necrotrophic pathogen Fusarium oxysporum. By challenging Fusarium-tolerant GCTCV-218 and susceptible Grand Naine Cavendish banana plants (which had been used in a previous characterization study) with the hemi-biotrophic Xanthomonas pathogen (a very important economical pathogen of banana), the two MNPR1, PR-1 and PR-3 genes were found to be sequentially expressed. Expression of these genes was more pronounced in the tolerant GCTCV-218 banana cultivar than in the sensitive Grand Naine cultivar. Comparative sequence analysis further showed that these two banana NPR1-like coding sequences had dissimilarities even within conserved functional domains; they grouped closely with other defense-related NPR1-like sequences and harboured defense cis-regulatory elements. Transformation of the coding sequences of both genes under the control of the 35S CaMV promoter/terminator sequences into npr1-2 Arabidopsis mutant complimented the phenotype of this mutant following infection with distinct classes of pathogens (biotrophic Hyaloperonospora, necrotrophic Botrytis and hemi-biotrophic Pseudomonas pathogens). These Infected-MNPR1-expressing plants had higher PR-1 transcript amounts with more reduced pathogen growth compared to non-transgenic npr1-2 Arabidopsis mutant plants. However, the difference in the two banana coding sequences did not translate into a differential pattern of response against the three different classes of pathogens used in this study. Further detailed studies are suggested to investigate the role of the MNPR1 promoter-coding sequences in the differential response to pathogens using a bananapathogen system. This study also addressed the question of whether cystosolic glutathione (GSH) is necessary for NPR1 transcription during systemic acquired resistance. Using Arabidopsis mutants (clt1clt2clt3) defective in cytosolic GSH biosynthesis and following infection with either Pseudomonas or Botrytis, NPR1 and PR-1 transcription was much reduced rendering the mutants more sensitive to pathogens compared to infected-wild-type i>Arabidopsis plants. Results from this study therefore implicate cytosolic glutathione as an essential antioxidant for the establishment of an effective defense response cascade.Thesis (PhD)--University of Pretoria, 2011.Plant Scienceunrestricte

A post-gene silencing bioinformatics protocol for plant-defence gene validation and underlying process identification: case study of the Arabidopsis thaliana NPR1

Advances in forward and reverse genetic techniques have enabled the discovery and identification of several plant defence genes based on quantifiable disease phenotypes in mutant populations. Existing models for testing the effect of gene inactivation or genes causing these phenotypes do not take into account eventual uncertainty of these datasets and potential noise inherent in the biological experiment used, which may mask downstream analysis and limit the use of these datasets. Moreover, elucidating biological mechanisms driving the induced disease resistance and influencing these observable disease phenotypes has never been systematically tackled, eliciting the need for an efficient model to characterize completely the gene target under consideration

Two different banana NPR1-like coding sequences confer similar protection against pathogens in Arabidopsis

Differences between the coding sequences of two banana homologues of the Non-expressor of Pathogenesis-Related 1 (NPR1) genes (MNPR1A and MNPR1B) were investigated as a possible cause for the differential activity of the two genes. Each of the MNPR1 coding sequences were expressed under the control of the cauliflower mosaic virus 35S promoter/terminator sequences in the transgenic Arabidopsis npr1-2 mutant. These MNPR1-expressing plants were then exposed to either the biotrophic oomycete Hyaloperonospora arabidopsidis, the necrotrophic fungus Botrytis cinerea, or the hemi-biotrophic bacterial pathogen Pseudomonas syringae. Expression of either MNPR1A or MNPR1B increased Pathogenesis-related 1 (PR-1) transcription in a similar manner in mutant plants and reduced pathogen growth, restoring resistance of the Arabidopsis npr1-2 mutant plants to pathogens. Sequence differences between MNPR1A and MNPR1B coding sequences did not affect MNPR1activity, suggesting a possible role for the involvement of other regulatory sequences in differential MNPR1 gene expression.Rockefeller Foundation and the University of Pretoria.http://link.springer.com/journal/12042hb2016Forestry and Agricultural Biotechnology Institute (FABI)Plant Scienc

Factors facilitating sustainable scientific partnerships between developed and developing countries

International scientific partnerships are key to the success of strategic investments in plant science research and the farm-level adoption of new varieties and technologies, as well as the coherence of agricultural policies across borders to address global challenges. Such partnerships result not only in a greater impact of published research enhancing the career development of early and later stage researchers, but they also ensure that advances in plant science and crop breeding technologies make a meaningful contribution to society by brokering acceptance of emerging solutions to the world problems. We discuss the evidence showing that despite a lack of funding, scientists in some African countries make a significant contribution to global science output. We consider the criteria for success in establishing long-term scientific partnerships between scientists in developing countries in Southern Africa (“the South”) and developed countries such as the UK (“the North”). We provide our own personal perspectives on the key attributes that lead to successful institutional collaborations and the establishment of sustainable networks of successful “North-South” scientific partnerships. In addition, we highlight some of the stumbling blocks which tend to hinder the sustainability of long-term “North-South” scientific networks. We use this personal knowledge and experiences to provide guidelines on how to establish and maintain successful long-term “North-South” scientific partnerships.National Research Foundation of South Africa, Winter Cereal Trust and African Union Research Grant Programme funded by the European Union.http://journals.sagepub.com/home/oaghj2021Forestry and Agricultural Biotechnology Institute (FABI)Plant Production and Soil Scienc

A phenornics approach to the analysis of the influence of glutathione on leaf area and abiotic stress tolerance in Arabidopsis thaliana

Reduced glutathione (GSH) is an abundant low molecular weight plant thiol. It fulfills multiple functions in plantbiology, many of which remain poorly characterized. Aphenomics approach was therefore used to investigate the effects of glutathione home ostasis on growth and stress tolerance in Arabidopsisthalian. Rosette leaf area was compared in mutants that are either defective in GSH synthesis (cad2, pad2, andrax1)or the exportofγ-glutamylcysteine and GSH from the chloroplast (clt) and in wild-type plants understandard growth conditions and following exposure to arange of abiotic stress treatments,including oxidative stress,waterstress,and high salt.In the absence of stress,the GSH synthes is mutants had a significantly lower leaf area than the wild type.Conversely,the clt mutant has a greater leaf area and a significantly reduced lateral rootdensity than the wild type.These findings demonstrate that cellular glutathione homeostasis exerts an influence on root architecture and on rosette area. An impaired capacity to synthesize GSH or a specific depletion of the cytosolic GSH pool did not adversely affect leaf are ainplants exposed to short-termabioticstress. However, the negative effects of long-term exposure to oxidative stress and high salt on leaf are awere less marked in the GSH synthesis mutants than the wild type. These findings demonstrate the importance of cellular glutathione homeostasis in the regulation of plant growth under optimal and stress conditions.FP7-PIRSES-GA-2008-230830 (LEGIM, Rosita E.Yocgo) and PITN-GA-2008-215174 (Chloroplast Signals,Daniel Schnaubelt).http://www.frontiersin.orghb201

From lateral root density to nodule number, the strigolactone analogue GR24 shapes the root architecture of Medicago truncatula

In the rhizosphere, strigolactones not only act as crucial signalling molecules in the communication of plants with parasitic weeds and arbuscular mycorrhiza, but they also play a key role in regulating different aspects of the root system. Here we investigated how strigolactones influence the root architecture of Medicago truncatula. We provide evidence that addition of the synthetic strigolactone analogue GR24 has an inhibitory effect on the lateral root density. Moreover, treatment with GR24 of Sinorhizobium meliloti-inoculated M. truncatula plants affects the nodule number both positively and negatively, depending on the concentration. Plants treated with 0.1 μM GR24 had a slightly increased number of nodules, whereas concentrations of 2 and 5 μM strongly reduced it. This effect was independent of the autoregulation of nodulation mechanism that is controlled by SUPER NUMERIC NODULE. Furthermore, we demonstrate that GR24 controls the nodule number through crosstalk with SICKLE-dependent ethylene signalling. Additionally, because the expression of the nodulation marker EARLY NODULATION11 was strongly reduced in GR24-treated plants, we concluded that strigolactones influence nodulation at a very early stage of the symbiotic interaction.European Union Seventh Framework Programme (EU-FP7-PIRSES-GA-2008–230830 LEGIM).J.F. is indebted to the Institut National de la Recherche Agronomique for a postdoctoral fellowship (Contrat Jeune Scientifique). C.D.C. is a predoctoral fellow of the Research Foundation-Flanders.http://jxb.oxfordjournals.org2016-01-30hb201

Erratum to "From lateral root density to nodule number, the strigolactone analogue GR24 shapes the root architecture of medicago truncatula" (vol 66, pg 137, 2015)

Erratum to http://prodinra.inra.fr/record/279289Erratum to "From lateral root density to nodule number, the strigolactone analogue GR24 shapes the root architecture of [i]medicago truncatula[/i]" (vol 66, pg 137, 2015