Le Corre V.,CNRS Agroecology Lab |
Kremer A.,French National Institute for Agricultural Research |
Kremer A.,University of Bordeaux 1
Molecular Ecology | Year: 2012
Most adaptive traits are controlled by large number of genes that may all together be the targets of selection. Adaptation may thus involve multiple but not necessarily substantial allele frequency changes. This has important consequences for the detection of selected loci and implies that a quantitative genetics framework may be more appropriate than the classical 'selective sweep' paradigm. Preferred methods to detect loci involved in local adaptation are based on the detection of 'outlier' values of the allelic differentiation F ST. A quantitative genetics framework is adopted here to review theoretical expectations for how allelic differentiation at quantitative trait loci (F STQ) relates to (i), neutral genetic differentiation (F ST) and (ii), phenotypic differentiation (Q ST). We identify cases where results of outlier-based methods are likely to be poor and where differentiation at selected loci conveys little information regarding local adaptation. A first case is when neutral differentiation is high, so that local adaptation does not necessitate increased differentiation. A second case is when local adaptation is reached via an increased covariance of allelic effects rather than via allele frequency changes, which is more likely under high gene flow when the number of loci is high and selection is recent. The comparison of theoretical predictions with observed data from the literature suggests that polygenic local adaptation involving only faint allele frequency changes are very likely in some species such as forest trees and for climate-related traits. Recent methodological improvements that may alleviate the weakness of F ST-based detection methods are presented. © 2012 Blackwell Publishing Ltd.
Delye C.,CNRS Agroecology Lab |
Jasieniuk M.,University of California at Davis |
Le Corre V.,CNRS Agroecology Lab
Trends in Genetics | Year: 2013
Resistance to herbicides in arable weeds is increasing rapidly worldwide and threatening global food security. Resistance has now been reported to all major herbicide modes of action despite the development of resistance management strategies in the 1990s. We review here recent advances in understanding the genetic bases and evolutionary drivers of herbicide resistance that highlight the complex nature of selection for this adaptive trait. Whereas early studied cases of resistance were highly herbicide-specific and largely under monogenic control, cases of greatest concern today generally involve resistance to multiple modes of action, are under polygenic control, and are derived from pre-existing stress response pathways. Although 'omics' approaches should enable unraveling the genetic bases of complex resistances, the appearance, selection, and spread of herbicide resistance in weed populations can only be fully elucidated by focusing on evolutionary dynamics and implementing integrative modeling efforts. © 2013 Elsevier Ltd.
Griffiths B.S.,Teagasc |
Philippot L.,CNRS Agroecology Lab
FEMS Microbiology Reviews | Year: 2013
Soil is increasingly under environmental pressures that alter its capacity to fulfil essential ecosystem services. To maintain these crucial soil functions, it is important to know how soil microorganisms respond to disturbance or environmental change. Here, we summarize the recent progress in understanding the resistance and resilience (stability) of soil microbial communities and discuss the underlying mechanisms of soil biological stability together with the factors affecting it. Biological stability is not solely owing to the structure or diversity of the microbial community but is linked to a range of other vegetation and soil properties including aggregation and substrate quality. We suggest that resistance and resilience are governed by soil physico-chemical structure through its effect on microbial community composition and physiology, but that there is no general response to disturbance because stability is particular to the disturbance and soil history. Soil stability results from a combination of biotic and abiotic soil characteristics and so could provide a quantitative measure of soil health that can be translated into practice. Interactions between soil physico-chemical properties and microbial species functional characteristics are key determinants of soil biological stability (resistance and resilience). © 2012 Federation of European Microbiological Societies.
Wendehenne D.,CNRS Agroecology Lab |
Gao Q.-M.,University of Kentucky |
Kachroo A.,University of Kentucky |
Kachroo P.,University of Kentucky
Current Opinion in Plant Biology | Year: 2014
Systemic acquired resistance (SAR) is a form of defense that protects plants against a broad-spectrum of secondary infections by related or unrelated pathogens. SAR related research has witnessed considerable progress in recent years and a number of chemical signals and proteins contributing to SAR have been identified. All of these diverse constituents share their requirement for the phytohormone salicylic acid, an essential downstream component of the SAR pathway. However, recent work demonstrating the essential parallel functioning of nitric oxide (NO)-derived and reactive oxygen species (ROS)-derived signaling together with SA provides important new insights in the overlapping pathways leading to SAR. This review discusses the potential significance of branched pathways and the relative contributions of NO/ROS-derived and SA-derived pathways in SAR. © 2014 Elsevier Ltd.
Rasul S.,CNRS Agroecology Lab
Plant signaling & behavior | Year: 2012
We investigated the production and function of nitric oxide (NO) in Arabidopsis thaliana leaf discs as well as whole plants elicited by oligogalacturonides (OGs). Using genetic, biochemical and pharmacological approaches, we provided evidence that OGs induced a Nitrate Reductase (NR)-dependent NO production together with an increased NR activity and NR transcripts accumulation. In addition, NO production was sensitive to the mammalian NOS inhibitor L-NAME. Intriguingly, L-NAME impaired OG-induced NR activity and did not further affect the remaining OG-induced NO production in the nia1nia2 mutant. These data suggest that the L-arginine and NR pathways, co-involved in NO production, do not work independently. Taking account these new data, we propose scenarios to explain NO production in response to biotic stress.
Delye C.,CNRS Agroecology Lab
Pest Management Science | Year: 2013
Non-target-site-based resistance (NTSR) can confer unpredictable cross-resistance to herbicides. However, the genetic determinants of NTSR remain poorly known. The current, urgent challenge for weed scientists is thus to elucidate the bases of NTSR so that detection tools are developed, the evolution of NTSR is understood, the efficacy of the shrinking herbicide portfolio is maintained and integrated weed management strategies, including fully effective herbicide applications, are designed and implemented. In this paper, the importance of NTSR in resistance to herbicides is underlined. The most likely way in which NTSR evolves-by accumulation of different mechanisms within individual plants-is described. The NTSR mechanisms, which can interfere with herbicide penetration, translocation and accumulation at the target site, and/or protect the plant against the consequences of herbicide action, are then reviewed. NTSR is a part of the plant stress response. As such, NTSR is a dynamic process unrolling over time that involves 'protectors' directly interfering with herbicide action, and also regulators controlling 'protector' expression. NTSR is thus a quantitative trait. On this basis, a three-step procedure is proposed, based on the use of the 'omics' (genomics, transcriptomics, proteomics or metabolomics), to unravel the genetic bases of NTSR. © 2012 Society of Chemical Industry.
Ochatt S.,CNRS Agroecology Lab
Biotechnology Advances | Year: 2013
The use and exploitation of electrophysiology with plant cells have witnessed a slow but steady increase for a number of purposes in recent years. First envisaged only as a tool for the recovery of somatic hybrid plants following protoplast electrofusion, or for transient and/or stable genetic transformation following electroporation-mediated entry of foreign genes into protoplasts and cells, electrophysiological studies with plant cells and tissues have since spanned into other areas, and particularly for the assessment of the possible effects of electric and electromagnetic fields on the subsequent growth and differentiation competences of the electro-treated cells. This review will critically discuss these various applications of electrophysiology and will also aim at analysing the fundamental physiological and physico-chemical mechanisms underlying them. © 2013 Elsevier Inc.
Duhoux A.,CNRS Agroecology Lab |
Delye C.,CNRS Agroecology Lab
PLoS ONE | Year: 2013
Variation in the expression of numerous genes is at the basis of plant response to environmental stresses. Non-target-site-based resistance to herbicides (NTSR), the major threat to grass weed chemical control, is governed by a subset of the genes involved in herbicide stress response. Quantitative PCR assays allowing reliable comparison of gene expression are thus key to identify genes governing NTSR. This work aimed at identifying a set of reference genes with a stable expression to be used as an internal standard for the normalisation of quantitative PCR data in studies investigating NTSR to herbicides inhibiting acetolactate synthase (ALS) in the major grass weed Lolium sp. Gene expression stability was assessed in plants resistant or sensitive to two ALS inhibitors, subjected or not to herbicide stress. Using three complementary approaches implemented in the programs BestKeeper, NormFinder and geNorm, cap-binding protein, glyceraldehyde-3-phosphate-dehydrogenase and ubiquitin were identified as the most suitable reference genes. This reference gene set can probably be used to study herbicide response in other weed species. It was used to compare the expression of the genes encoding two herbicide target enzymes (ALS and acetyl-coenzyme A carboxylase) and five cytochromes P450 (CYP) with potential herbicide-degrading activity between plants resistant or sensitive to ALS inhibitors. Overall, herbicide application enhanced CYP gene expression. Constitutive up-regulation of all CYP genes observed in resistant plants compared to sensitive plants suggested enhanced secondary metabolism in the resistant plants. Comprehensive transcriptome studies associated to gene expression analyses using the reference gene set validated here are required to unravel NTSR genetic determinants. © 2013 Duhoux, Délye.
Darmency H.,CNRS Agroecology Lab
Pest Management Science | Year: 2013
The rapid adoption of genetically engineered herbicide-resistant crop varieties (HRCVs)-encompassing 83% of all GM crops and nearly 8% of the worldwide arable area-is due to technical efficiency and higher returns. Other herbicide-resistant varieties obtained from genetic resources and mutagenesis have also been successfully released. Although the benefit for weed control is the main criteria for choosing HRCVs, the pleiotropic costs of genes endowing resistance have rarely been investigated in crops. Here the available data of comparisons between isogenic resistant and susceptible varieties are reviewed. Pleiotropic harmful effects on yield are reported in half of the cases, mostly with resistance mechanisms that originate from genetic resources and mutagenesis (atrazine in oilseed rape and millet, trifluralin in millet, imazamox in cotton) rather than genetic engineering (chlorsulfuron and glufosinate in some oilseed rape varieties, glyphosate in soybean). No effect was found for sethoxydim and bromoxynil resistance. Variable minor effects were found for imazamox, chlorsulfuron, glufosinate and glyphosate resistance. The importance of the breeding plan and the genetic background on the emergence of these effects is pointed out. Breeders' efforts to produce better varieties could compensate for the yield loss, which eliminates any possibility of formulating generic conclusions on pleiotropic effects that can be applied to all resistant crops. © 2013 Society of Chemical Industry.
Calderon K.,CNRS Agroecology Lab
ISME Journal | Year: 2016
Soil ecosystems worldwide are subjected to marked modifications caused by anthropogenic disturbances and global climate change, resulting in microbial diversity loss and alteration of ecosystem functions. Despite the paucity of studies, restoration ecology provides an appropriate framework for testing the potential of manipulating soil microbial communities for the recovery of ecosystem functioning. We used a reciprocal transplant design in experimentally altered microbial communities to investigate the effectiveness of introducing microbial communities in degraded soil ecosystems to restore N-cycle functioning. Microbial diversity loss resulted in alternative compositional states associated with impaired N-cycle functioning. Here, the addition of complex microbial communities to these altered communities revealed a pivotal role of deterministic community assembly processes. The diversity of some alternative compositional states was successfully increased but without significant restoration of soil N-cycle functioning. However, in the most degraded alternative state, the introduction of new microbial communities caused an overall decrease in phylogenetic diversity and richness. The successful soil colonization by newly introduced species for some compositional states indicates that priority effects could be overridden when attempting to manipulate microbial communities for soil restoration. Altogether, our result showed consistent patterns within restoration treatments with minor idiosyncratic effects. This suggests the predominance of deterministic processes and the predictability of restoration trajectories, which could be used to guide the effective management of microbial community assemblages for ecological restoration of soils.The ISME Journal advance online publication, 24 June 2016; doi:10.1038/ismej.2016.86. © 2016 International Society for Microbial Ecology