Olivier Leroux

Ghent University | UGhent · Department of Plants and Crops | Department of Biology

Hereditary symbioses with bacteria are common in the animal kingdom, but relatively unexplored in plants. Several plant species form associations with bacteria in their leaves, which is called leaf symbiosis.

This work describes the development of a novel method for quantitative mapping of Hg and Se in mushroom fruit body tissues with laser ablation coupled to inductively coupled plasma-mass spectrometry (LA-ICP-MS). Different parameters of the protocol for preparation of the standards used for quantification via external calibration were assessed, e.g....

Variation in life styles occurs in the fungal genus Verticillium. Verticillium longisporum causes diseases on several brassicaceous crops, including cauliflower, but has not been observed causing damage in broccoli. Verticillium isaacii has been frequently isolated from fields of horticultural crops, but the majority of the isolates has exhibited l...

While elemental mapping via LA-ICP-MS – i.e. mapping the distribution of elements across the surface of a solid material – has shown a substantial evolution towards higher speed, sensitivity and...

Hereditary symbioses have the potential to drive transgenerational effects, yet the mechanisms responsible for transmission of heritable plant symbionts are still poorly understood. The leaf symbiosis between Dioscorea sansibarensis and the bacterium Orrella dioscoreae offers an appealing model system to study how heritable bacteria are transmitted...

The timing of abiotic stress elicitors on wood formation largely affects xylem traits that determine xylem efficiency and vulnerability. Nonetheless, seasonal variability of elevated CO2 (eCO2) effects on tree functioning under drought remains largely unknown. To address this knowledge-gap, one-year-old aspen (Populus tremula L.) trees were grown u...

About 90% of all land plants form mycorrhiza to facilitate the acquisition of essential nutrients such as phosphorus, nitrogen, and sometimes carbon. Based on the morphology of the interaction and the identity of the interacting plants and fungi, four major mycorrhizal types have been distinguished: arbuscular mycorrhiza (AM), ectomycorrhizal (EcM)...

Somatic embryogenesis in Coffea spp. is important for mass production and genetic engineering. Coffee is an exceptional case, as somatic embryogenesis can be induced by applying a cytokinin such as 2iP as the only plant growth regulator. 1-(2-(2-Hydroxyethyl)phenyl)-3-(3-(trifluoromethoxy)phenyl)urea (3TFM-2HE) and 1-(3-bromo-5-(trifluoromethoxy)ph...

Selection of high-yielding traits in cereal plants led to a continuous increase in productivity. However, less effort was made to select on adaptive traits, favorable in adverse and harsh environments. Under current climate change conditions and the knowledge that cereals are staple foods for people worldwide, it is highly important to shift focus...

A vibrating microtome is widely used to produce good-quality sections of plant organs or tissues. This method allows for an improved preservation of antigenicity and structure and is compatible with most (immuno)cytochemical staining procedures.

Foliar water uptake (FWU), the direct uptake of water into leaves, is a global phenomenon, having been observed in an increasing number of plant species. Despite the growing recognition of its functional relevance, our understanding of how FWU occurs and which foliar surface structures are implicated, is limited. In this study, fluorescent and ioni...

In order to improve the understanding of plant water relations under drought stress, the water use behavior of two Fragaria x ananassa Duch. cultivars, contrasting in their drought stress phenotype, is identified. Under drought, stomatal closure is gradual in Figaro. Based on this, we associate Figaro with conservative water use behavior. Contraril...

Agrochemicals provide vast potential to improve plant productivity, because they are easy to implement at low cost while not being restricted by species barriers as compared to breeding strategies. Despite the general interest, only few compounds with growth-promoting activity have been described so far. Here, we add cis-cinnamic acid (c-CA) to the...

BACKGROUND & AIMS: The bacterial leaf nodule symbiosis is an interaction where bacteria are housed in specialised structures in the leaves of their plant host. In the Rubiaceae plant family, host plants interact with Burkholderia bacteria. This interaction might play a role in the host plant defence system. It is unique due to its high specificity;...

Generally, tree species load photoassimilates passively into the phloem, while herbaceous species load actively. These phloem loading strategies have implications for phloem sugar concentration and growth potential. Whereas, in previous research, phloem loading identification was performed with 14 C-autoradiography, we suggest 11 C-autoradiography,...

Plants are known to respond to warming temperatures. Few studies, however, have included the temperature experienced by the parent plant in the experimental design, in spite of the importance of this factor for population dynamics. We investigated the phenological and growth responses of seedlings of two key temperate tree species (Fagus sylvatica...

Background and aims The bacterial leaf nodule symbiosis is a close interaction between endophytes and their plant hosts, mainly within the coffee family. The interaction between Rubiaceae species and Burkholderia bacteria is unique due to its obligate nature, high specificity, and predominantly vertical transmission of the endophytes to the next ge...

In situ detection of Burkholderia endophytes in longitudinal sections of the three additional P. punctata embryos using FISH. (A) Merged epifluorescence images of the outer space of the embryo in close proximity of the cotyledons, showing FISH-labelled endophyte (red, arrow). (B) Same detail as (A), stained with TBO after FISH labelling. (C) Merged...

Detailed information on the identification of the endophytes in the different plant structures of Psychotria punctata. List of the detected endophytes, the plant structure from which their DNA was extracted, host plant acquisition numbers of the living collection at the Botanic Garden Meise (BGM), the identity of the endophytes on species level, Ge...

Background: Plant reproductive output is determined by a complex set of factors including resource availability, pollination success and pre-dispersal predation. Disentangling the relative contribution of each factor is critical to underpin the factors determining plant fitness. Aims: To unravel the relative contributions of initial reproductive ef...

Background and aims: A key structural adaptation of vascular plants was the evolution of specialized vascular and mechanical tissues, innovations likely to have generated novel cell wall architectures. While collenchyma is a strengthening tissue typically found in growing organs of angiosperms, a similar tissue occurs in the petiole of the fern As...

Grapevines are characterized by a period of irreversible stem shrinkage around the onset of ripening of the grape berries. Since this shrinkage is unrelated to meteorological conditions or drought, it is often suggested that it is caused by the increased sink strength of the grape berries during this period. However, no studies so far have experime...

Folates (B9 vitamins) are essential cofactors in one-carbon metabolism. Since C1 transfer reactions are involved in synthesis of nucleic acids, proteins, lipids and other biomolecules, as well as in epigenetic control, folates are vital for all living organisms. This work presents the first complete study of a plant DHFR-TS (dihydrofolate reductase...

* Heat girdling is a method to estimate the relative contribution of phloem vs xylem water flow to fruit growth. The heat girdling process is assumed to destroy all living tissues, including the phloem, without affecting xylem conductivity. However, to date, the assumption that xylem is not affected by heat girdling remains unproven. * In this stud...

Folates (B9 vitamins) are essential cofactors in one-carbon metabolism. Since C1 transfer reactions are involved in synthesis of nucleic acids, proteins, lipids, and other biomolecules, as well as in epigenetic control, folates are vital for all living organisms. This work presents a complete study of a plant DHFR-TS (dihydrofolate reductase-thymid...

Because the plant cell wall provides the first line of defence against biotic and abiotic assaults, its functional integrity needs to be maintained under stress conditions. Through a phenotype-based compound screening approach we identified a novel cellulose synthase inhibitor, designated C17. C17 administration depletes cellulose synthase complexe...

While it is kno3wn that complex tissues with specialized functions emerged during land plant evolution, it is not clear how cell wall polymers and their structural variants are associated with specific tissues or cell types. Moreover, due to the economic importance of many flowering plants, ferns have been largely neglected in cell wall comparative...

At present, the importance of sample preparation equipment for electron microscopy represents the driving force behind major breakthroughs in microscopy and cell biology. In this paper we present an introduction to the most commonly used cryo-fixation techniques, with special attention paid towards high-pressure freezing followed by freeze substitu...

Plants are very well adapted to growth in ultraviolet-B (UV-B) containing light. In Arabidopsis thaliana, many of these adaptations are mediated by the UV-B receptor UV RESISTANCE LOCUS 8 (UVR8). Using small amounts of supplementary UV-B light, we observed changes in the shape of rosette leaf blades. Wild type plants show more pronounced epinasty o...

Background and Aims Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper fu...

Background and AimsInnovations in vegetative and reproductive characters were key factors in the evolutionary history of land plants and most of these transformations, including dramatic changes in life cycle structure and strategy, necessarily involved cell-wall modifications. To provide more insight into the role of cell walls in effecting change...

The majority of microbial mediated soil processes depend on availability of organic matter (OM), water and air. Because of its ability to visualize the 3D architecture of soil non-destructively, X-ray computed tomography (CT) is becoming a widespread tool for studying soil pore network structure. However, phase determination of pore space, soil OM,...

Background and AimsEnvironmental change is increasingly impacting ecosystems worldwide. However, our knowledge about the interacting effects of various drivers of global change on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. This study examines populations of poorly regenerating and threatened common j...

Plant cell walls are essential for most aspects of plant growth, development, and survival, including cell division, expansive cell growth, cell-cell communication, biomechanical properties, and stress responses. Therefore, characterizing cell wall diversity contributes to our overall understanding of plant evolution and development. Recent biochem...

Laminae of Adiantum raddianum Presl., a fern belonging to the family Pteridaceae, are characterised by the presence of epidermal fibre-like cells under the vascular bundles. These cells were thought to contain silica bodies, but their thickened walls leave no space for intracellular silica suggesting it may actually be deposited within their walls....

Background Collenchyma has remained in the shadow of commercially exploited mechanical tissues such as wood and fibres, and therefore has received little attention since it was first described. However, collenchyma is highly dynamic, especially compared with sclerenchyma. It is the main supporting tissue of growing organs with walls thickening duri...

Common juniper (Juniperus communis L.) populations in northwest European lowlands are currently declining in size and number. An important cause of this decline is a lack of natural regeneration. Low seed viability seems to be one of the main bottlenecks in this process. Previous research revealed a negative relation between seed viability and both...

Background and aims – In Cyperaceae, the single-ovuled, usually triangular gynoecia are widely considered to have a basic number of three carpels, often reduced to two, resulting in dimerous pistils. However, laterally flattened dimerous pistils cannot be explained by any existing carpel reduction theories, because a single stigma in median positio...

and aims – Recent molecular studies validate a broad definition of Cyperus (Cyperaceae) uniting genera previously scattered in Cyperoideae. First indication of their affinity with Cyperus was obtained through embryography. Cyperus consists of a paraphyletic C3 Cyperus and monophyletic C4 Cyperus. In this study, we aim to check and clarify the putat...

Bacterial 16S rRNA gene sequences isolated from algae (excluding BLAST hits) included in the phylogenetic analysis. (DOCX)

A wide-range maximum likelihood tree showing the phylogenetic positions of endophytic clones and DGGE bands. Phylogenies were inferred from 16S rRNA gene sequences determined in this study (in bold), BLAST hits (see Table 1), Bacteroidetes, Proteobacteria and Mollicutes type strains, and algae-associated bacteria described in the literature (see Su...

Associations between marine seaweeds and bacteria are widespread, with endobiotic bacterial-algal interactions being described for over 40 years. Also within the siphonous marine green alga Bryopsis, intracellular bacteria have been visualized by electron microscopy in the early '70s, but were up to now never molecularly analyzed. To study this par...

The anatomy of Equisetum stems is characterized by the occurrence of vallecular and carinal canals. Previous studies on the carinal canals in several Equisetum species suggest that they convey water from one node to another. Cell wall composition and ultrastructure have been studied using immunocytochemistry and electron microscopy, respectively. S...

Cell wall appositions (CWAs), formed by the deposition of extra wall material at the contact site with microbial organisms, are an integral part of the response of plants to microbial challenge. Detailed histological studies of CWAs in fern roots do not exist. Using light and electron microscopy we examined the (ultra)structure of CWAs in the outer...

In the current model of gravitropism, negative gravitropic (upward) growth of the shoot of a dicotyledonous plant involves sedimentation of starch-containing plastids (statoliths) in the endodermis (starch sheath). Here we show that high levels of brassinosteroids (BRs) counteract gravitropic growth, while BR deficiency enhances gravitropism irresp...

Extraxylary helical cell wall thickenings in vascular plants are not well documented, except for those in orchid velamen tissues which have been studied extensively. Reports on their occurrence in ferns exist, but detailed information is missing. The aim of this study is to focus on the broad patterns of structure and composition and to study the t...

How the diverse polysaccharides present in plant cell walls are assembled and interlinked into functional composites is not known in detail. Here, using two novel monoclonal antibodies and a carbohydrate-binding module directed against the mannan group of hemicellulose cell wall polysaccharides, we show that molecular recognition of mannan polysacc...

'Loxoscaphoid' Asplenium species are morphologically a remarkably distinct group of Aspleniaceae. Except for two preliminary chromosome counts of Asplenium theciferum, the cytology of this group of species has, however, been largely unstudied. Chromosome counts were obtained by acetocarmine squash preparations of one mitotic cell and several meioti...

Since the development of X-ray computed tomography as a medical diagnostic tool, it was adapted and extended for many scientific applications, including plant structure research. As for many biological studies, sample preparation is of major importance to obtain good-quality images. Therefore, we present a new preparation method for fresh material...

A list of 59 newly recorded Pteridophytes from the Bukit Baka- Bukit Raya National Park in Central Kalimantan is presented. Nine species are recorded for Indonesian Borneo (Kalimantan) for the first time: Diplazium polycarpum, Pronephrium peltatum var. persetiferum, Pteris asperula, Selliguea enervis, Sphaerostephanos latebrosus, Sphaerostephanos r...

Projections of cell wall material into the intercellular spaces between parenchymatic cells have been observed since the mid-19th century. Histochemical staining suggested that these intercellular protuberances are probably pectic in nature, but uncertainties about their origin, composition and biological function(s) have remained. Using electron a...

High-quality sections are indispensable for many scientific studies. Most published methods are often time-consuming or require special devices. We present an easy, quick and low-cost method for oriented embedding of thin structures using glycol methacrylate resin and self-constructed, reusable embedding tools made of overhead transparencies. This...