The distribution of lectins across the phylum Nematoda : a genome-wide search

Nematodes are a very diverse phylum that has adapted to nearly every ecosystem. They have developed specialized lifestyles, dividing the phylum into free-living, animal, and plant parasitic species. Their sheer abundance in numbers and presence in nearly every ecosystem make them the most prevalent animals on earth. In this research nematode-specific profiles were designed to retrieve predicted lectin-like domains from the sequence data of nematode genomes and transcriptomes. Lectins are carbohydrate-binding proteins that play numerous roles inside and outside the cell depending on their sugar specificity and associated protein domains. The sugar-binding properties of the retrieved lectin-like proteins were predicted in silico. Although most research has focused on C-type lectin-like, galectin-like, and calreticulin-like proteins in nematodes, we show that the lectin-like repertoire in nematodes is far more diverse. We focused on C-type lectins, which are abundantly present in all investigated nematode species, but seem to be far more abundant in free-living species. Although C-type lectin-like proteins are omnipresent in nematodes, we have shown that only a small part possesses the residues that are thought to be essential for carbohydrate binding. Curiously, hevein, a typical plant lectin domain not reported in animals before, was found in some nematode species

Horizontal gene transfer contributes to plant evolution : the case of Agrobacterium T-DNAs

Horizontal gene transfer (HGT) can be defined as the acquisition of genetic material from another organism without being its offspring. HGT is common in the microbial world including archaea and bacteria, where HGT mechanisms are widely understood and recognized as an important force in evolution. In eukaryotes, HGT now appears to occur more frequently than originally thought. Many studies are currently detecting novel HGT events among distinct lineages using next-generation sequencing. Most examples to date include gene transfers from bacterial donors to recipient organisms including fungi, plants, and animals. In plants, one well-studied example of HGT is the transfer of the tumor-inducing genes (T-DNAs) from some Agrobacterium species into their host plant genomes. Evidence of T-DNAs from Agrobacterium spp. into plant genomes, and their subsequent maintenance in the germline, has been reported in Nicotiana, Linaria and, more recently, in Ipomoea species. The transferred genes do not produce the usual disease phenotype, and appear to have a role in evolution of these plants. In this paper, we review previous reported cases of HGT from Agrobacterium, including the transfer of T-DNA regions from Agrobacterium spp. to the sweetpotato [ Ipomoea batatas (L.) Lam.] genome which is, to date, the sole documented example of a naturally-occurring incidence of HGT from Agrobacterium to a domesticated crop plant. We also discuss the possible evolutionary impact of T-DNA acquisition on plants

The role of knowledge in student opinions on genetically modified organisms : an intervention study

Biotechnology, which includes genetic modification (GM), is often considered to be a controversial topic. Large amounts of factual information on GM as well as opinions are widely spread, which can affect people’s opinions and attitudes towards GM. This paper aims to investigate the nature of students’ acquisition of new factual information about genetically modified organisms (GMOs), and how this can be related to how they cope with new factual scientific information and opinions. As such, an intervention study involving 575 sixth year secondary school students was set op. Before, during and after the intervention, students completed a questionnaire measuring their knowledge, perceived risks and benefits, as well as attitudes towards and willingness to eat (WTE) GMOs. The results indicated that acquiring new scientific information increased students’ scores related to perceived benefits, and attitudes, while the scores on risk perception decreased. Hearing others’ opinion on GMOs (combined pro- and anti-GM) had the opposite effect on the related student scores. In addition, the results suggested that the order in which opinions and factual information are addressed in class does not affect students’ attitudes and WTE GMOs as long as both are considered. However, students’ perception of risks and benefits differ depending on the order of the intervention phases. Based on these findings and the perceived fluctuations in the studied variables throughout the intervention, it is recommended that both the factual scientific information as well as the controversial GM debate should be addressed in class as early as possible in order to develop clear and balanced scientific conceptions as well as a personal opinion

Sensitivity towards DMI fungicides and haplotypic diversity of their CYP51 target in the Mycosphaerella graminicola population of Flanders

Septoria leaf blotch, caused by the fungus Mycosphaerella graminicola, is the most important wheat disease in Northwestern Europe, and is currently controlled by fungicide applications. Since the spread of resistance to methyl benzimidazole carbamates (MBCs) and quinone outside inhibitors (QoIs) in European countries, reliable control is mainly dependent upon sterol 14 alpha-demethylation inhibitors (DMIs). In the last decades however, a slow shift towards reduced sensitivity of M. graminicola to DMIs has been observed. This shift is caused mainly by mutations in the CYP51 gene encoding the 14 alpha-demethylase target protein for these fungicides. In this work, M. graminicola isolates were sampled at fields spread over Flanders, Belgium. In vitro assays were used to analyze the sensitivity of the Flemish M. graminicola population towards different DMIs. Sequencing of the CYP51 gene of these isolates allowed us to identify and map the haplotypes in this population. The results showed that there is a large variability in DMI sensitivity between the isolates, even within one field, which is reflected in a high diversity in CYP51 haplotypes within the M. graminicola population in Flanders. Next to some haplotypes that were not described in literature before, we found that the population is dominated by CYP51 haplotypes which were previously associated with increased resistance towards DMIs

Evolution of GHF5 endoglucanase gene structure in plant-parasitic nematodes: no evidence for an early domain shuffling event

Background Endo-1,4-beta-glucanases or cellulases from the glycosyl hydrolase family 5 (GHF5) have been found in numerous bacteria and fungi, and recently also in higher eukaryotes, particularly in plant-parasitic nematodes (PPN). The origin of these genes has been attributed to horizontal gene transfer from bacteria, although there still is a lot of uncertainty about the origin and structure of the ancestral GHF5 PPN endoglucanase. It is not clear whether this ancestral endoglucanase consisted of the whole gene cassette, containing a catalytic domain and a carbohydrate-binding module (CBM, type 2 in PPN and bacteria) or only of the catalytic domain while the CBM2 was retrieved by domain shuffling later in evolution. Previous studies on the evolution of these genes have focused primarily on data of sedentary nematodes, while in this study, extra data from migratory nematodes were included. Results Two new endoglucanases from the migratory nematodes Pratylenchus coffeae and Ditylenchus africanus were included in this study. The latter one is the first gene isolated from a PPN of a different superfamily (Sphaerularioidea); all previously known nematode endoglucanases belong to the superfamily Tylenchoidea (order Rhabditida). Phylogenetic analyses were conducted with the PPN GHF5 endoglucanases and homologous endoglucanases from bacterial and other eukaryotic lineages such as beetles, fungi and plants. No statistical incongruence between the phylogenetic trees deduced from the catalytic domain and the CBM2 was found, which could suggest that both domains have evolved together. Furthermore, based on gene structure data, we inferred a model for the evolution of the GHF5 endoglucanase gene structure in plant-parasitic nematodes. Our data confirm a close relationship between Pratylenchus spp. and the root knot nematodes, while some Radopholus similis endoglucanases are more similar to cyst nematode genes. Conclusions We conclude that the ancestral PPN GHF5 endoglucanase gene most probably consisted of the whole gene cassette, i.e. the GHF5 catalytic domain and the CBM2, rather than that it evolved by domain shuffling. Our evolutionary model for the gene structure in PPN GHF5 endoglucanases implies the occurrence of an early duplication event, and more recent gene duplications at genus or species level

Salicylic acid biosynthesis in plants

Salicylic acid (SA) is an important plant hormone that is best known for mediating host responses upon pathogen infection. Its role in plant defense activation is well established, but its biosynthesis in plants is not fully understood. SA is considered to be derived from two possible pathways; the ICS and PAL pathway, both starting from chorismate. The importance of both pathways for biosynthesis differs between plant species, rendering it hard to make generalizations about SA production that cover the entire plant kingdom. Yet, understanding SA biosynthesis is important to gain insight into how plant pathogen responses function and how pathogens can interfere with them. In this review, we have taken a closer look at how SA is synthesized and the importance of both biosynthesis pathways in different plant species

Interplay between carotenoids, abscisic acid and jasmonate guides the compatible rice-Meloidogyne graminicola interaction

In this study, we have characterized the role of carotenoids and chlorophyll in the compatible interaction between the sedentary root knot nematode (RKN) Meloidogyne graminicola and the monocot model plant rice (Oryza sativa). Previous transcriptome data showed a differential expression of carotenoid and chlorophyll biosynthesis genes in nematode-induced giant cells and gall tissue. Metabolite measurement showed that galls indeed accumulate chlorophyll a, b and carotenoids, as well as the hormone abscisic acid (ABA). When ABA was externally applied on rice plants, or when ABA-biosynthesis was inhibited, a significant increase in gall formation and nematode development was found, showing the complex role of ABA in this interaction. ABA application suppressed jasmonic acid (JA) levels in the plants, while ABA-biosynthesis inhibition lead to increased JA levels confirming an antagonism between ABA and JA in rice roots. In addition, combined applications of ABA and JA showed that the ABA-effect can overcome JA-induced defense. Based on these observations, we hypothesized that the accumulation of chlorophyll and carotenoid precursors would be beneficial to nematode infection. Indeed, when chemically blocking the carotenoid biosynthesis pathway at different steps, which leads to differential accumulation of carotenoids and chlorophyll in the plants, a positive and clear link between accumulation of carotenoids and chlorophyll and rice susceptibility to RKN was detected