Molecular Characterization and Functional Analysis of the Hb-hsp90-1 Gene in Relation to Temperature Changes in Heterorhabditis bacteriophora

Temperature Effects on Expression Levels of hsp Genes in Eggs and Second-Stage Juveniles of Meloidogyne hapla Chitwood, 1949

Meloidogyne hapla is one of the most important nematode pathogens. It is a sedentary, biotrophic parasite of plants that overwinters in the soil or in diseased roots. The development of M. hapla is temperature dependent. Numerous studies have been performed on the effect of temperature on the development of M. hapla, but only a few of them analyzed the heat shock protein (hsp) genes. The aim of the study was to perform expression profiling of eight hsp genes (Mh-hsp90, Mh-hsp1, Mh-hsp4, Mh-hsp6, Mh-hsp60, Mh-dnj19, Mh-hsp43, and Mh-hsp12.2) at two development stages of M. hapla, i.e., in eggs and second-stage juveniles (J2). The eggs and J2 were incubated under cold stress (5 °C), heat stress (35 °C, 40 °C), and non-stress (10 °C, 20 °C, and 30 °C) conditions. Expression profiling was performed by qPCR. It was demonstrated that only two genes, Mh-hsp60 and Mh-dnj19, have been upregulated by heat and cold stress at both development stages. Heat stress upregulated the expression of more hsp genes than cold stress did. The level of upregulation of most hsp genes was more marked in J2 than in eggs. The obtained results suggest that the Mh-hsp90 and Mh-hsp1 genes can be used as bioindicators of environmental impacts on nematodes of the Meloidogyne genus.

Heat Shock Proteins as Potential Indicators of Induced Stress in Nematodes

Heat shock proteins (HSPs) in all animals studied to date constitute potential indicators of stress, under various environmental conditions. The goal of this chapter is to show, for the first time, the suitability of the approach based on evaluation of the expression levels of heat shock proteins, as good indicators of stress induced in nematodes by the cultivation of resistant plant varieties or by other potential stressors.

Entomopathogenic nematodes and their symbiotic bacteria: from genes to field uses

The term "microbial control" has been used to describe the use of microbial pathogens (bacteria, viruses, or fungi) or entomopathogenic nematodes (EPNs) to control various insect pest populations. EPNs are among the best biocontrol agents, and major developments in their use have occurred in recent decades, with many surveys having been conducted all over the world to identify EPNs that may have potential in the management of insect pests. For nematodes, the term "entomopathogenic" means "causing disease to insects" and is mainly used in reference to the bacterial symbionts of Steinernema and Heterorhabditis (Xenorhabdus and Photorhabdus, respectively), which cause EPN infectivity. A compendium of our multiannual experiences on EPN surveys and on their collection, identification, characterization, and use in agro-forestry ecosystems is presented here to testify and demonstrate once again that biological control with EPNs is possible and offers many advantages over chemicals, such as end-user safety, minimal damage to natural enemies, and lack of environmental pollution, which are essential conditions for an advanced IPM strategy.

Effect of Vicia sativa L. on Motility, Mortality and Expression Levels of hsp Genes in J2 Stage of Meloidogyne hapla

Assuming that the seeds of Vicia sativa L. have a stressful effect on J2 stage Meloidogyne hapla, we undertook research on the effect of these seeds on the motility and mortality of J2 and determined the expression levels of selected hsp genes in J2. The assessment of the effect of V. sativa seeds on the motility of M. hapla specimens consisted of observing the movement of J2 immersed in a seed diffusate or in a tomato root filtrate at temperatures of 10, 17, and 21°C. In J2 treated with V. sativa (cv. Ina) seed diffusates, the expression level of hsp genes was determined by qPCR. J2 exposed to V. sativa diffusates were found to lose their motility, while their mortality did not exceed 30%. J2 in the seed diffusate were characterized by an increase in the expression levels of the Mh-hsp90, Mh-hsp1, and Mh-hsp43 genes. It is suggested that the hsp90 gene may be a potential bioindicator of the environmental impact on Meloidogyne nematodes. The impaired ability to move in J2 of M. hapla is attributable to the occurrence of V. sativa seeds in their habitat. These studies may contribute to developing methods of reducing crop damage caused by M. hapla.

Type Strains of Entomopathogenic Nematode-Symbiotic Bacterium Species, Xenorhabdus szentirmaii (EMC) and X. budapestensis (EMA), Are Exceptional Sources of Non-Ribosomal Templated, Large-Target-Spectral, Thermotolerant-Antimicrobial Peptides (by Both), and Iodinin (by EMC)

Antimicrobial multidrug resistance (MDR) is a global challenge, not only for public health, but also for sustainable agriculture. Antibiotics used in humans should be ruled out for use in veterinary or agricultural settings. Applying antimicrobial peptide (AMP) molecules, produced by soil-born organisms for protecting (soil-born) plants, seems a preferable alternative. The natural role of peptide-antimicrobials, produced by the prokaryotic partner of entomopathogenic-nematode/bacterium (EPN/EPB) symbiotic associations, is to sustain monoxenic conditions for the EPB in the gut of the semi-anabiotic infective dauer juvenile (IJ) EPN. They keep pathobiome conditions balanced for the EPN/EPB complex in polyxenic (soil, vanquished insect cadaver) niches. Xenorhabdus szentirmaii DSM16338(T) (EMC), and X. budapestensis DSM16342(T) (EMA), are the respective natural symbionts of EPN species Steinernema rarum and S. bicornutum. We identified and characterized both of these 15 years ago. The functional annotation of the draft genome of EMC revealed 71 genes encoding non-ribosomal peptide synthases, and polyketide synthases. The large spatial Xenorhabdus AMP (fabclavine), was discovered in EMA, and its biosynthetic pathway in EMC. The AMPs produced by EMA and EMC are promising candidates for controlling MDR prokaryotic and eukaryotic pathogens (bacteria, oomycetes, fungi, protozoa). EMC releases large quantity of iodinin (1,6-dihydroxyphenazine 5,10-dioxide) in a water-soluble form into the media, where it condenses to form spectacular water-insoluble, macroscopic crystals. This review evaluates the scientific impact of international research on EMA and EMC.

Novel Nematode-Killing Protein-1 (Nkp-1) from a Marine Epiphytic Bacterium Pseudoalteromonas tunicata

Drug resistance among parasitic nematodes has resulted in an urgent need for the development of new therapies. However, the high re-discovery rate of anti-nematode compounds from terrestrial environments necessitates a new repository for future drug research. Marine epiphytes are hypothesised to produce nematicidal compounds as a defence against bacterivorous predators, thus representing a promising yet underexplored source for anti-nematode drug discovery. The marine epiphytic bacterium Pseudoalteromonas tunicata is known to produce several bioactive compounds. Screening heterologously expressed genomic libraries of P. tunicata against the nematode Caenorhabditis elegans, identified as an E. coli clone (HG8), shows fast-killing activity. Here we show that clone HG8 produces a novel nematode-killing protein-1 (Nkp-1) harbouring a predicted carbohydrate-binding domain with weak homology to known bacterial pore-forming toxins. We found bacteria expressing Nkp-1 were able to colonise the C. elegans intestine, with exposure to both live bacteria and protein extracts resulting in physical damage and necrosis, leading to nematode death within 24 h of exposure. Furthermore, this study revealed C. elegans dar (deformed anal region) and internal hatching may act as a nematode defence strategy against Nkp-1 toxicity. The characterisation of this novel protein and putative mode of action not only contributes to the development of novel anti-nematode applications in the future but reaffirms the potential of marine epiphytic bacteria as a new source of novel biomolecules.

Pratylenchus vovlasi sp. Nov. (Nematoda: Pratylenchidae) on Raspberries in North Italy with a Morphometrical and Molecular Characterization

Root-lesion nematode species rank third only to root-knot and cyst nematodes as having the greatest economic impact on crops worldwide. A survey of plant-parasitic nematodes associated with decaying raspberries (Rubus sp.) in northern Italy revealed that root-lesion nematodes were the most frequently occurring species among other phytonematodes. Several Pratylenchus species have been associated with Rubus sp. in Canada (Quebec, British Columbia) and USA (North Carolina, Maryland, New Jersey) including P. penetrans and P. crenatus. In the roots and rhizosphere of symptomatic raspberries, nematodes of two Pratylenchus spp. were detected. Detailed morphometrics of the two root-lesion nematode isolates were consistent with Pratylenchus crenatus and with an undescribed Pratylenchus species. The extracted nematodes were observed and measured as live and fixed materials and subsequently identified by integrative taxonomy (morphometrically and molecularly). The latter species is described herein as Pratylenchus vovlasi sp. nov., resulting morphometrically closest to P. mediterraneus and phylogenetically to P. pratensis. The molecular identification of Pratylenchus vovlasi sp. nov. was carried out by sequencing the ITS region, D2-D3 expansion domains of the 28S rRNA gene and a partial region of the nuclear hsp90 gene. ITS-RFLP and sequence analyses revealed that Pratylenchus vovlasi sp. nov. had species-specific restriction profiles with no corresponding sequences present in the database. The phylogenetic relationships with ITS and D2-D3 sequences placed the Pratylenchus vovlasi sp. nov. in a clade with P. pratensis and P. pseudopratensis. This research confirms the occurrence of cryptic biodiversity within the genus Pratylenchus as well as the need for an integrative approach to the identification of Pratylenchus species.