393,335 research outputs found
Plant basal resistance: genetics, biochemistry, and impacts on plant-biotic interactions
No full textBasal resistance depends largely on a diverse range of defence mechanisms that become active upon attack by pathogens or insects. These mechanisms range from rapid stomatal closure and production of reactive oxygen species, to callose deposition and defence gene induction. It is commonly assumed that the speed and intensity of these inducible defences determines the effectiveness of basal resistance. The present dissertation describes different aspects of basal resistance in Arabidopsis thaliana and Zea mays. Chapter 2 of the dissertation describes natural variation between Arabidopsis accessions in basal defence responsiveness to pathogen-associated molecular patterns (PAMPs) and the defence hormone salicylic acid (SA). Quantitative trait loci (QTL) analysis identified different loci regulating the sensitivity of PAMP-induced callose and SA-induced defence gene expression. One QTL controlling SA responsiveness was found to contribute to basal resistance against Pseudomonas syringae pv. tomato. In Chapter 3, the contribution of benzoxazinoids (BXs) in basal resistance of maize is described, using maize bx1 mutant lines that are impaired in the first dedicated step of BX biosynthesis. Compared to wild-type lines, bx1 lines displayed reduced penetration resistance against aphids and fungus. Furthermore, infestation of wild-type plants by aphids and fungi stimulated the conversion of DIMBOA-glucoside into HDMBOA-glucoside and DIMBOA, which was most pronounced in the apoplast of challenged tissues. Interestingly, these events preceded major tissue damage or symptom development, suggesting that BX-dependent basal resistance does not necessarily depend on tissue damage. Upon further investigation of wild-type and bx1 mutant lines, we observed significantly reduced callose deposition in bx1 plants after PAMP treatment. Furthermore, DIMBOA infiltration of the apoplast mimicked PAMP-induced callose in wild-type plants. Hence, DIMBOA acts as a regulatory signal in the expression of cell wall-based basal resistance of maize. BXs have also been reported to act as allelopathic signals belowground, which are further investigated in Chapter 4. Chromatographic analysis revealed that DIMBOA is the dominant BX species in root exudates of maize. To investigate the impact of BXs on root-colonizing rhizobacteria, transcriptome analysis was performed of DIMBOA-treated Pseudomonas putida KT2440. This global analysis pointed towards increased transcription of bacterial genes that are involved in break-down of aromatic metabolites and chemotaxis. The latter response was confirmed by in vitro assays, which demonstrated chemotaxis of the bacteria towards DIMBOA. Furthermore, root colonisation assays with GFP-expressing P. putida KT2440 revealed that wild-type plants allowed more bacterial colonization than BX-deficient bx1 plants, indicating that BXs can recruit rhizobacteria from the soil. Preliminary results that are presented in Chapter 5 show that root colonization by P. putida KT2440 primes aboveground basal defences against herbivores, thereby further highlighting the central and multifaceted function of DIMBOA in maize basal resistance
Toward a Molecular Understanding of Plant Hormone Actions
No full textPlants rely on a diverse set of small-molecule hormones to regulate every aspect of their biological processes including development, growth, and adaptation. Since the discovery of the first plant hormone, auxin, hormones have always been at the frontier of plant biology. Although the physiological functions of most plant hormones have been studied for decades, the last 15–20 years have seen dramatic progress in our understanding of the molecular mechanisms of hormone actions. The publication of the whole-genome sequences of the model systems of Arabidopsis and rice, together with the advent of multidisciplinary approaches, has opened the door to successful experimentation on plant hormone actions.SCI(E)PubMed中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)EDITORIAL [email protected]; [email protected]
The role of climate and plant functional trade-offs in shaping global biome and biodiversity patterns
No full textAim: Two of the oldest observations in plant geography are the increase in plant diversity from the poles towards the tropics and the global geographic distribution of vegetation physiognomy (biomes). The objective of this paper is to use a process-based vegetation model to evaluate the relationship between modelled and observed global patterns of plant diversity and the geographic distribution of biomes.Location: The global terrestrial biosphere.Methods: We implemented and tested a novel vegetation model aimed at identifying strategies that enable plants to grow and reproduce within particular climatic conditions across the globe. Our model simulates plant survival according to the fundamental ecophysiological processes of water uptake, photosynthesis, reproduction and phenology. We evaluated the survival of an ensemble of 10,000 plant growth strategies across the range of global climatic conditions. For the simulated regional plant assemblages we quantified functional richness, functional diversity and functional identity.Results: A strong relationship was found (correlation coefficient of 0.75) between the modelled and the observed plant diversity. Our approach demonstrates that plant functional dissimilarity increases and then saturates with increasing plant diversity. Six of the major Earth biomes were reproduced by clustering grid cells according to their functional identity (mean functional traits of a regional plant assemblage). These biome clusters were in fair agreement with two other global vegetation schemes: a satellite image classification and a biogeography model (kappa statistics around 0.4).Main conclusions: Our model reproduces the observed global patterns of plant diversity and vegetation physiognomy from the number and identity of simulated plant growth strategies. These plant growth strategies emerge from the first principles of climatic constraints and plant functional trade-offs. Our study makes important contributions to furthering the understanding of how climate affects patterns of plant diversity and vegetation physiognomy from a process-based rather than a phenomenological perspective
Sensor-based phenotyping of above-ground plant-pathogen interactions
No full textPlant pathogens cause yield losses in crops worldwide. Breeding for improved disease resistance and management by precision agriculture are two approaches to limit such yield losses. Both rely on detecting and quantifying signs and symptoms of plant disease. To achieve this, the field of plant phenotyping makes use of non-invasive sensor technology. Compared to invasive methods, this can offer improved throughput and allow for repeated measurements on living plants. Abiotic stress responses and yield components have been successfully measured with phenotyping technologies, whereas phenotyping methods for biotic stresses are less developed, despite the relevance of plant disease in crop production. The interactions between plants and pathogens can lead to a variety of signs (when the pathogen itself can be detected) and diverse symptoms (detectable responses of the plant). Here, we review the strengths and weaknesses of a broad range of sensor technologies that are being used for sensing of signs and symptoms on plant shoots, including monochrome, RGB, hyperspectral, fluorescence, chlorophyll fluorescence and thermal sensors, as well as Raman spectroscopy, X-ray computed tomography, and optical coherence tomography. We argue that choosing and combining appropriate sensors for each plant-pathosystem and measuring with sufficient spatial resolution can enable specific and accurate measurements of above-ground signs and symptoms of plant disease.ImPhys/Computational Imagin
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
The Plant Short-Chain Dehydrogenase (SDR) superfamily:genome-wide inventory and diversification patterns
No full textBackground Short-chain dehydrogenases/reductases (SDRs) form one of the largest and oldest NAD(P)(H) dependent oxidoreductase families. Despite a conserved 'Rossmann-fold' structure, members of the SDR superfamily exhibit low sequence similarities, which constituted a bottleneck in terms of identification. Recent classification methods, relying on hidden-Markov models (HMMs), improved identification and enabled the construction of a nomenclature. However, functional annotations of plant SDRs remain scarce. Results Wide-scale analyses were performed on ten plant genomes. The combination of hidden Markov model (HMM) based analyses and similarity searches led to the construction of an exhaustive inventory of plant SDR. With 68 to 315 members found in each analysed genome, the inventory confirmed the over-representation of SDRs in plants compared to animals, fungi and prokaryotes. The plant SDRs were first classified into three major types --- 'classical', 'extended' and 'divergent' --- but a minority (10 % of the predicted SDRs) could not be classified into these general types ('unknown' or 'atypical' types). In a second step, we could categorize the vast majority of land plant SDRs into a set of 49 families. Out of these 49 families, 35 appeared early during evolution since they are commonly found through all the Green Lineage. Yet, some SDR families --- tropinone reductase-like proteins (SDR65C), 'ABA2-like'-NAD dehydrogenase (SDR110C), 'salutaridine/menthone-reductase-like' proteins (SDR114C), 'dihydroflavonol 4-reductase'-like proteins (SDR108E) and 'isoflavone-reductase-like' (SDR460A) proteins --- have undergone significant functional diversification within vascular plants since they diverged from Bryophytes. Interestingly, these diversified families are either involved in the secondary metabolism routes (terpenoids, alkaloids, phenolics) or participate in developmental processes (hormone biosynthesis or catabolism, flower development), in opposition to SDR families involved in primary metabolism which are poorly diversified. Conclusion The application of HMMs to plant genomes enabled us to identify 49 families that encompass all Angiosperms ('higher plants') SDRs, each family being sufficiently conserved to enable simpler analyses based only on overall sequence similarity. The multiplicity of SDRs in plant kingdom is mainly explained by the diversification of large families involved in different secondary metabolism pathways, suggesting that the chemical diversification that accompanied the emergence of vascular plants acted as a driving force for SDR evolution
Advances in plant gene-targeted and functional markers: a review
No full textPublic genomic databases have provided new directions for molecular marker development and initiated a shift in
the types of PCR-based techniques commonly used in plant science. Alongside commonly used arbitrarily amplified
DNA markers, other methods have been developed. Targeted fingerprinting marker techniques are based on the
well-established practices of arbitrarily amplified DNA methods, but employ novel methodological innovations such
as the incorporation of gene or promoter elements in the primers. These markers provide good reproducibility and
increased resolution by the concurrent incidence of dominant and co-dominant bands. Despite their promising
features, these semi-random markers suffer from possible problems of collision and non-homology analogous to
those found with randomly generated fingerprints. Transposable elements, present in abundance in plant genomes,
may also be used to generate fingerprints. These markers provide increased genomic coverage by utilizing specific
targeted sites and produce bands that mostly seem to be homologous. The biggest drawback with most of these
techniques is that prior genomic information about retrotransposons is needed for primer design, prohibiting
universal applications. Another class of recently developed methods exploits length polymorphism present in arrays
of multi-copy gene families such as cytochrome P450 and β-tubulin genes to provide cross-species amplification
and transferability. A specific class of marker makes use of common features of plant resistance genes to generate
bands linked to a given phenotype, or to reveal genetic diversity. Conserved DNA-based strategies have limited
genome coverage and may fail to reveal genetic diversity, while resistance genes may be under specific
evolutionary selection. Markers may also be generated from functional and/or transcribed regions of the genome
using different gene-targeting approaches coupled with the use of RNA information. Such techniques have the
potential to generate phenotypically linked functional markers, especially when fingerprints are generated from the
transcribed or expressed region of the genome. It is to be expected that these recently developed techniques will
generate larger datasets, but their shortcomings should also be acknowledged and carefully investigated
Flooding and low oxygen responses in plants
No full textThe world is currently experiencing dramatic increases in flood events impacting on natural vegetation and crops. Flooding often results in low O2 status in root tissues during waterlogging, but sometimes also in shoot tissues when plants become completely submerged. Plants possess a suite of traits enabling tissue aeration and/or adjusted metabolism during hypoxia or even in the absence of O2. This special issue of Functional Plant Biology presents key papers for plant scientists on the quest to further address and improve flood tolerance of terrestrial plants. The papers address low O2 responses in roots, shoots or whole plants in controlled laboratory conditions or in the field situation using natural wetland plants as models as well as economically important crops, such as rice, wheat and barley. The studies advance our understanding of low O2 responses in plant tissues as caused by O2 shortage during flooding. However, in most instances, submergence not only leads to hypoxic or anoxic tissues, but inundation in water also results in accumulation of CO2 and the important plant hormone ethylene. Thus, carefully designed laboratory studies are often needed to unravel the mechanistic relationships between a combined decline in O2 followed by increases in CO2 and ethylene at tissue as well as on the cellular level
Effects of experimental snowmelt and rain on dispersal of six plant species
No full textWater flows affect dispersal of propagules of many plant species, and rivers and streams are therefore very important dispersal vectors. However, small water flows such as trough rain and snowmelt are much more common, but their effects on dispersal are barely studied. The importance of this form of dispersal deserves attention, especially when considering that climate change is predicted to change the amounts of rain and snow worldwide. Dispersal through melting snow and rain was addressed experimentally, using artificial soils mounted on slopes with different angles and subjected to a melting snow pack or an equivalent amount of dripping water. Seeds on the soil moved on average 3.02 cm (+/- 1.81 SE) in rain treatments and 0.23 cm (+/- 0.3 SE) in snowmelt treatments. Tracking plastic granules in field conditions further showed that snowmelt exhibited minimal dispersal capacity. Dispersal distances by rain were enhanced by increasing slope angles and with decreasing seed volume. Given that many species in cold environments have small seeds, dispersal by rain could provide an important (secondary) dispersal mechanism in these habitats
- …
