Rhizomania: Hide and Seek of Polymyxa betae and the Beet Necrotic Yellow Vein Virus with Beta vulgaris.

The molecular interactions between Polymyxa betae, the protist vector of sugar beet viruses, beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania, and Beta vulgaris have not been extensively studied. Here, the transmission of BNYVV to sugar beet by P. betae zoospores was optimized using genetically characterized organisms. Molecular interactions of aviruliferous and viruliferous protist infection on sugar beet were highlighted by transcriptomic analysis. P. betae alone induced limited gene expression changes in sugar beet, as a biotrophic asymptomatic parasite. Most differentially expressed plant genes were down-regulated and included resistance gene analogs and cell wall peroxidases. Several enzymes involved in stress regulation, such as the glutathione-S-transferases, were significantly induced. With BNYVV, the first stages of the P. betae life cycle on sugar beet were accelerated with a faster increase of relative protist DNA level and an earlier appearance of sporangia and sporosori in plants roots. A clear activation of plant defenses and the modulation of genes involved in plant cell wall metabolism were observed. The P. betae transcriptome in the presence of BNYVV revealed induction of genes possibly involved in the switch to the survival stage. The interactions were different depending on the presence or absence of the virus. P. betae alone alleviates plant defense response, playing hide-and-seek with sugar beet and allowing for their mutual development. Conversely, BNYVV manipulates plant defense and promotes the rapid invasion of plant roots by P. betae. This accelerated colonization is accompanied by the development of thick-walled resting spores, supporting the virus survival. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Metabolic Analysis of the Development of the Plant-Parasitic Cyst Nematodes Heterodera schachtii and Heterodera trifolii by Capillary Electrophoresis Time-of-Flight Mass Spectrometry.

The cyst nematodes Heterodera schachtii and Heterodera trifolii, whose major hosts are sugar beet and clover, respectively, damage a broad range of plants, resulting in significant economic losses. Nematodes synthesize metabolites for organismal development and social communication. We performed metabolic profiling of H. schachtii and H. trifolii in the egg, juvenile 2 (J2), and female stages. In all, 392 peaks were analyzed by capillary electrophoresis time-of-flight mass spectrometry, which revealed a lot of similarities among metabolomes. Aromatic amino acid metabolism, carbohydrate metabolism, choline metabolism, methionine salvage pathway, glutamate metabolism, urea cycle, glycolysis, gluconeogenesis, coenzyme metabolism, purine metabolism, pyrimidine metabolism, and tricarboxylic acid (TCA) cycle for energy conversion (ß-oxidation and branched-chain amino acid metabolism) energy storage were involved in all stages studied. The egg and female stages synthesized higher levels of metabolites compared to the J2 stage. The key metabolites detected were glycerol, guanosine, hydroxyproline, citric acid, phosphorylcholine, and the essential amino acids Phe, Leu, Ser, and Val. Metabolites, such as hydroxyproline, acetylcholine, serotonin, glutathione, and glutathione disulfide, which are associated with growth and reproduction, mobility, and neurotransmission, predominated in the J2 stage. Other metabolites, such as SAM, 3PSer, 3-ureidopropionic acid, CTP, UDP, UTP, 3-hydroxy-3-methylglutaric acid, 2-amino-2-(hydroxymethyl-1,3-propanediol, 2-hydroxy-4-methylvaleric acid, Gly Asp, glucuronic acid-3 + galacturonic acid-3 Ser-Glu, citrulline, and γ-Glu-Asn, were highly detected in the egg stage. Meanwhile, nicotinamide, 3-PG, F6P, Cys, ADP-Ribose, Ru5P, S7P, IMP, DAP, diethanolamine, p-Hydroxybenzoic acid, and γ-Glu-Arg_divalent were unique to the J2 stage. Formiminoglutamic acid, nicotinaminde riboside + XC0089, putrescine, thiamine 2,3-dihydroxybenzoic acid, 3-methyladenine, caffeic acid, ferulic acid, m-hydrobenzoic acid, o- and p-coumaric acid, and shikimic acid were specific to the female stage. Overall, highly similar identities and quantities of metabolites between the corresponding stages of the two species of nematode were observed. Our results will be a valuable resource for further studies of physiological changes related to the development of nematodes and nematode-plant interactions.

Rapid and Visual Detection of Heterodera schachtii Using Recombinase Polymerase Amplification Combined with Cas12a-Mediated Technology.

Heterodera schachtii is a well-known cyst nematode that causes serious economic losses in sugar beet production every year. Rapid and visual detection of H. schachtii is essential for more effective prevention and control. In this study, a species-specific recombinase polymerase amplification (RPA) primer was designed from a specific H. schachtii sequence-characterized amplified region (SCAR) marker. A band was obtained in reactions with DNA from H. schachtii, but absent from nontarget cyst nematodes. The RPA results could be observed by the naked eye, using a lateral flow dipstick (LFD). Moreover, we combined CRISPR technology with RPA to identify positive samples by fluorescence detection. Sensitivity analysis indicated that 10-4 single cysts and single females, 4-3 single second-stage juveniles, and a 0.001 ng genomic DNA template could be detected. The sensitivity of the RPA method for H. schachtii detection is not only higher than that of PCR and qPCR, but can also provide results in <1 h. Consequently, the RPA assay is a practical and useful diagnostic tool for early diagnosis of plant tissues infested by H. schachtii. Sugar beet nematodes were successfully detected in seven of 15 field sugar beet root samples using the RPA assay. These results were consistent with those achieved by conventional PCR, indicating 100% accuracy of the RPA assay in field samples. The RPA assay developed in the present study has the potential for use in the direct detection of H. schachtii infestation in the field.

Re-targeting of a plant defense protease by a cyst nematode effector.

Plants mount defense responses during pathogen attacks, and robust host defense suppression by pathogen effector proteins is essential for infection success. 4E02 is an effector of the sugar beet cyst nematode Heterodera schachtii. Arabidopsis thaliana lines expressing the effector-coding sequence showed altered expression levels of defense response genes, as well as higher susceptibility to both the biotroph H. schachtii and the necrotroph Botrytis cinerea, indicating a potential suppression of defenses by 4E02. Yeast two-hybrid analyses showed that 4E02 targets A. thaliana vacuolar papain-like cysteine protease (PLCP) 'Responsive to Dehydration 21A' (RD21A), which has been shown to function in the plant defense response. Activity-based protein profiling analyses documented that the in planta presence of 4E02 does not impede enzymatic activity of RD21A. Instead, 4E02 mediates a re-localization of this protease from the vacuole to the nucleus and cytoplasm, which is likely to prevent the protease from performing its defense function and at the same time, brings it in contact with novel substrates. Yeast two-hybrid analyses showed that RD21A interacts with multiple host proteins including enzymes involved in defense responses as well as carbohydrate metabolism. In support of a role in carbohydrate metabolism of RD21A after its effector-mediated re-localization, we observed cell wall compositional changes in 4E02 expressing A. thaliana lines. Collectively, our study shows that 4E02 removes RD21A from its defense-inducing pathway and repurposes this enzyme by targeting the active protease to different cell compartments.

Molecular insights into the compatible and incompatible interactions between sugar beet and the beet cyst nematode.

BACKGROUND: Sugar beet (Beta vulgaris subsp. vulgaris) is an economically important crop that provides nearly one third of the global sugar production. The beet cyst nematode (BCN), Heterodera schachtii, causes major yield losses in sugar beet and other crops worldwide. The most effective and economic approach to control this nematode is growing tolerant or resistant cultivars. To identify candidate genes involved in susceptibility and resistance, the transcriptome of sugar beet and BCN in compatible and incompatible interactions at two time points was studied using mRNA-seq. RESULTS: In the susceptible cultivar, most defense-related genes were induced at 4 dai while suppressed at 10 dai but in the resistant cultivar Nemakill, induction of genes involved in the plant defense response was observed at both time points. In the compatible interaction, alterations in phytohormone-related genes were detected. The effect of exogenous application of Methyl Jasmonate and ET-generator ethephon on susceptible plants was therefore investigated and the results revealed significant reduction in plant susceptibility. Genes putatively involved in the resistance of Nemakill were identified, such as genes involved in phenylpropanoid pathway and genes encoding CYSTM domain-containing proteins, F-box proteins, chitinase, galactono-1,4-lactone dehydrogenase and CASP-like protein. Also, the transcriptome of the BCN was analyzed in infected root samples and several novel potential nematode effector genes were found. CONCLUSIONS: Our data provides detailed insights into the plant and nematode transcriptional changes occurring during compatible and incompatible interactions between sugar beet and BCN. Many important genes playing potential roles in susceptibility or resistance of sugar beet against BCN, as well as some BCN effectors with a potential role as avr proteins were identified. In addition, our findings indicate the effective role of jasmonate and ethylene in enhancing sugar beet defense response against BCN. This research provides new molecular insights into the plant-nematode interactions that can be used to design novel management strategies against BCN.

BvcZR3 and BvHs1pro-1 Genes Pyramiding Enhanced Beet Cyst Nematode (Heterodera schachtii Schm.) Resistance in Oilseed Rape (Brassica napus L.).

Beet cyst nematode (Heterodera schachtii Schm.) is one of the most damaging pests in sugar beet growing areas around the world. The Hs1pro-1 and cZR3 genes confer resistance to the beet cyst nematode, and both were cloned from sugar beet translocation line (A906001). The translocation line carried the locus from B. procumbens chromosome 1 including Hs1pro-1 gene and resistance gene analogs (RGA), which confer resistance to Heterodera schachtii. In this research, BvHs1pro-1 and BvcZR3 genes were transferred into oilseed rape to obtain different transgenic lines by A. tumefaciens mediated transformation method. The cZR3Hs1pro-1 gene was pyramided into the same plants by crossing homozygous cZR3 and Hs1pro-1 plants to identify the function and interaction of cZR3 and Hs1pro-1 genes. In vitro and in vivo cyst nematode resistance tests showed that cZR3 and Hs1pro-1 plants could be infested by beet cyst nematode (BCN) juveniles, however a large fraction of penetrated nematode juveniles was not able to develop normally and stagnated in roots of transgenic plants, consequently resulting in a significant reduction in the number of developed nematode females. A higher efficiency in inhibition of nematode females was observed in plants expressing pyramiding genes than in those only expressing a single gene. Molecular analysis demonstrated that BvHs1pro-1 and BvcZR3 gene expressions in oilseed rape constitutively activated transcription of plant-defense related genes such as NPR1 (non-expresser of PR1), SGT1b (enhanced disease resistance 1) and RAR1 (suppressor of the G2 allele of skp1). Transcript of NPR1 gene in transgenic cZR3 and Hs1pro-1 plants were slightly up-regulated, while its expression was considerably enhanced in cZR3Hs1pro-1 gene pyramiding plants. The expression of EDS1 gene did not change significantly among transgenic cZR3, Hs1pro-1 and cZR3Hs1pro-1 gene pyramiding plants and wild type. The expression of SGT1b gene was slightly up-regulated in transgenic cZR3 and Hs1pro-1 plants compared with the wild type, however, its expression was not changed in cZR3Hs1pro-1 gene pyramiding plant and had no interaction effect. RAR1 gene expression was significantly up-regulated in transgenic cZR3 and cZR3Hs1pro-1 genes pyramiding plants, but almost no expression was found in Hs1pro-1 transgenic plants. These results show that nematode resistance genes from sugar beet were functional in oilseed rape and conferred BCN resistance by activation of a CC-NBS-LRR R gene mediated resistance response. The gene pyramiding had enhanced resistance, thus offering a novel approach for the BCN control by preventing the propagation of BCN in oilseed rape. The transgenic oilseed rape could be used as a trap crop to offer an alternative method for beet cyst nematode control.

Disruption of the Pathogenicity and Sex Ratio of the Beet Cyst Nematode Heterodera schachtii by Host-Delivered RNA Interference.

The beet cyst nematode (BCN) Heterodera schachtii causes serious damage and yield losses in numerous important crops worldwide. This study examines the efficacy of three types of transgenic Arabidopsis RNA interference (RNAi) lines to decrease the biological activity of this devastating nematode. The first RNAi construct (E1E2-RNAi) targets two nematode endoglucanase genes, which are involved in BCN pathogenicity, the second construct (MSP-RNAi) contains a fragment corresponding to the major sperm protein transcript necessary for BCN development and reproduction, and the third construct (E1E2MSP-RNAi) comprises all three target fragments. Transcript expression profiles of the target genes in all biological stages of the nematode were determined for the initial inoculated population and the resulting progeny. Bioassay data under indoor aseptic cultivation indicated that feeding on these RNAi lines did not affect pathogenic activity and reproductive capacity of the initial population, whereas inoculating the progeny into new transgenic plants corresponding with the lines from which they were recovered reduced the nematode penetration and the number of eggs per cyst. In addition, the male/female ratio increased more than the double, and the effects of RNAi continued in the second generation of the nematodes, because the progeny derived from E1E2-RNAi and E1E2MSP-RNAi lines showed an impaired ability to infect wild-type plants.

A novel picornavirus-like genome from transcriptome sequencing of sugar beet cyst nematode represents a new putative genus.

Analysis of transcriptome sequence data from eggs and second-stage juveniles (J2s) of sugar beet cyst nematode (SBCN, Heterodera schachtii) identified the full-length genome of a positive-sense single-stranded RNA virus, provisionally named sugar beet cyst nematode virus 1 (SBCNV1). The SBCNV1 sequence was detected in both eggs and J2s, indicating its possible vertical transmission. The 9503-nucleotide genome sequence contains a single long open reading frame, which was predicted to encode a polyprotein with conserved domains for picornaviral structural proteins proximal to its amino terminus and RNA helicase, cysteine proteinase and RNA-dependent RNA polymerase (RdRp) conserved domains proximal to its carboxyl terminus, hallmarks of viruses belonging to the order Picornavirales. Phylogenetic analysis of the predicted SBCNV1 RdRp amino acid sequence indicated that the SBCNV1 sequence is most closely related to members of the family Secoviridae, which includes genera of nematode-transmitted plant-infecting viruses. SBCNV1 represents the first fully sequenced viral genome from SBCN.

The cyst nematode effector protein 10A07 targets and recruits host posttranslational machinery to mediate its nuclear trafficking and to promote parasitism in Arabidopsis.

Plant-parasitic cyst nematodes synthesize and secrete effector proteins that are essential for parasitism. One such protein is the 10A07 effector from the sugar beet cyst nematode, Heterodera schachtii, which is exclusively expressed in the nematode dorsal gland cell during all nematode parasitic stages. Overexpression of H. schachtii 10A07 in Arabidopsis thaliana produced a hypersusceptible phenotype in response to H. schachtii infection along with developmental changes reminiscent of auxin effects. The 10A07 protein physically associates with a plant kinase and the IAA16 transcription factor in the cytoplasm and nucleus, respectively. The interacting plant kinase (IPK) phosphorylates 10A07 at Ser-144 and Ser-231 and mediates its trafficking from the cytoplasm to the nucleus. Translocation to the nucleus is phosphorylation dependent since substitution of Ser-144 and Ser-231 by alanine resulted in exclusive cytoplasmic accumulation of 10A07. IPK and IAA16 are highly upregulated in the nematode-induced syncytium (feeding cells), and deliberate manipulations of their expression significantly alter plant susceptibility to H. schachtii in an additive fashion. An inactive variant of IPK functioned antagonistically to the wild-type IPK and caused a dominant-negative phenotype of reduced plant susceptibility. Thus, exploitation of host processes to the advantage of the parasites is one mechanism by which cyst nematodes promote parasitism of host plants.

Molecular Characterization and Identification of Stubby Root Nematode Species From Multiple States in the United States.

Stubby root nematodes (SRN) are important plant parasites infecting many crops and widely distributed in many regions of the United States. SRN transmit Tobacco rattle virus, which causes potato corky ringspot disease, thereby having a significant economic impact on the potato industry. In 2015 to 2017, 184 soil samples and 16 nematode suspensions from North Dakota, Minnesota, Idaho, Oregon, Washington, South Carolina, North Carolina, and Florida were assayed for the presence of SRN. SRN were found in 106 soil samples with population densities of 10 to 320 SRN per 200 g of soil and in eight of the nematode suspensions. Sequencing of ribosomal DNA (rDNA) or species-specific polymerase chain reaction assays revealed the presence of four SRN species, including Paratrichodorus allius, P. minor, P. porosus, and Trichodorus obtusus. Accordingly, their rDNA sequences were characterized by analyzing D2-D3 of 28S rDNA, 18S rDNA, and internal transcribed spacer (ITS) rDNA obtained in this study and retrieved from GenBank. Both intra- and interspecies variations were higher in ITS rDNA than 18S rDNA and D2-D3 of 28S rDNA. Based on phylogenetic analysis, the four SRN species formed a monophyletic group, with P. allius more closely related to P. porosus than P. minor and T. obtusus. Indel variation of ITS2 rDNA was present in P. allius populations from the same geographic regions. This study documented the occurrence of SRN species across multiple states. The intra- and interspecies genetic diversity of rDNA in this study will provide more information for understanding the evolutionary relationships of SRN and will be valuable for future studies of SRN species identification and management.

Effect of Cuscuta campestris parasitism on the physiological and anatomical changes in untreated and herbicide-treated sugar beet.

The effects of field dodder on physiological and anatomical processes in untreated sugar beet plants and the effects of propyzamide on field dodder were examined under controlled conditions. The experiment included the following variants: N-noninfested sugar beet plants (control); I - infested sugar beet plants (untreated), and infested plants treated with propyzamide (1500 g a.i. ha-1 (T1) and 2000 g a.i. ha-1(T2)). The following parameters were checked: physiological-pigment contents (chlorophyll a, chlorophyll b, total carotenoids); anatomical -leaf parameters: thickness of epidermis, parenchyma and spongy tissue, mesophyll and underside leaf epidermis, and diameter of bundle sheath cells; petiole parameters: diameter of tracheid, petiole hydraulic conductance, xylem surface, phloem cell diameter and phloem area in sugar beet plants. A conventional paraffin wax method was used to prepare the samples for microscopy. Pigment contents were measured spectrophotometrically after methanol extraction. All parameters were measured: prior to herbicide application (0 assessment), then 7, 14, 21, 28 and 35 days after application (DAA). Field dodder was found to affect the pigment contents in untreated sugar beet plants, causing significant reductions. Conversely, reduction in the treated plants decreased 27% to 4% for chlorophyll a, from 21% to 5% for chlorophyll b, and from 28% to 5% for carotenoids (T1). Also, in treatment T2, reduction decreased in infested and treated plants from 19% to 2% for chlorophyll a, from 21% to 2% for chlorophyll b, from 23% to 3% for carotenoids and stimulation of 1% and 2% was observed 28 and 35 DAA, respectively. Plants infested (untreated) by field dodder had lower values of most anatomical parameters, compared to noninfested plants. The measured anatomical parameters of sugar beet leaves and petiole had significantly higher values in noninfested plants and plants treated with propyzamide than in untreated plants. Also, the results showed that propyzamide is an adequate herbicide for control of field dodder at the stage of early infestation.

[ANTINEMATICIDAL ACTIVITY OF METABOLITES PRODUCED BY SOIL STREPTOMYCETE].

GOAL: To study in vitro the antinematicide activity of soil streptomycetes metabolite and bioformulations based on them against root-knot, cyst and leaf nematodes of species. METHODS: Action of streptomycetes metabolites and their bioformulations were determined in vitro against larvae at two age of root-knot nematode M incognita (Kofoid & White, 1919) Chitwood 1949 and sugar beet cyst nematode H. schachtii A. Schmidt 1871, and leaf nematodes ofAphlenchoides genus by cultivation them in solutions of biomass ethanol extracts separate individual components metabolites and bioformulations during 24 hours. Nematicide and nematistatic effects of the substances were evaluated by the change in the motility activity of the nematodes. RESULTS: Soil streptomycetes S. violaceus IMV Ac-5027, S. averinitilis IMV Ac-5015 and metabolite bioformulations based on them (Violar, Aver- com and Avercom-nova, respectively) showed significant nematicidal activity against plant pathogenic nematodes M incognita and H. schachtii. The biomass extracts of S. avermiti- lis IMV Ac-5015 and S. violaceus IMV Ac-5027 caused 100 % death of nematodes, and S. netropsis IMV Ac-5025 caused only 75 % mortality during 24 hours of action. Using an antibiotic complex from S. violaceus IMV Ac-5027 was divided on six fractions that were different from the avermectin complex. Purified fractions of individual antibiotic complex of S. violaceus IMV Ac-5 027 have a negative impact against the root-knot nematode M incognita. The highest nematicidal activity showed fractions #4 and #5 since their efficiency was over 90 % after a 0.5 hours of action. Nematicidal efficiency of fractions ## 1, 2, 3 and 6 remained between 72.6-86.2 % during 24 hours of action. Fractions 4 and 5 showed high nematicidal effectiveness against leaf nematodes of Aphelenchoides genus where 90-95 % level of helminthes death was observed after 4 hours of action. Among created complex metabolite bioformulations Avercom-nova was the most effective which caused 100 % mortality of nematodes M incognita and H. schachtii after 24 hours of action. Bioformu- lation Violar caused 96.6-96.8 and 95.2-97.0 % of death of nematodes M incognita and H. schachtii, after 24 hours of action. Phytovit based on S. netropsis IMV Ac-5025 showed low nematicide activity against of nematodes, which did not exceed 15.2-18.4 % of their death after 24 hour of action. Bioformulations based on streptomycetes metabolites did not inferior to chemical insecticide Konfidor Maxi, which caused the death of 93.3-94.6 % nematodes at doses recommended by the manufacturer. CONCLUSION: Soil streptomycetes S. violaceus IV Ac-5027 and S. avermitilis IMV Ac-5015 are promising producers for creation of bioformulations with nematicidal activity against plant-parasitic nematode of M incoenita and H. schachtii.

Heterozygote deficits in cyst plant-parasitic nematodes: possible causes and consequences.

Deviations of genotypic frequencies from Hardy-Weinberg equilibrium (HWE) expectations could reveal important aspects of the biology of populations. Deviations from HWE due to heterozygote deficits have been recorded for three plant-parasitic nematode species. However, it has never been determined whether the observed deficits were due (i) to the presence of null alleles, (ii) to a high level of consanguinity and/or (iii) to a Wahlund effect. The aim of the present work was, while taking into the possible confounding effect of null alleles, to disentangle consanguinity and Wahlund effect in natural populations of those three economically important cyst nematodes using microsatellite markers: Globodera pallida, G. tabacum and Heterodera schachtii, pests of potato, tobacco and sugar beet, respectively. The results show a consistent pattern of heterozygote deficiency in the three nematode species sampled at the spatial scale of the host plant. We demonstrate that the prevalence of null alleles is weak and that heterozygote deficits do not have a single origin. Our results suggested that it is restricted dispersal that leads to heterozygote deficits through both consanguinity and substructure, which effects can be linked to soil movement, cyst density, and the number of generations per year. We discuss potential implications for the durability of plant resistances that are used to protect crops against parasites in which mating between relatives occur. While consanguineous mating leads to homozygosity at all loci, including loci governing avirulence/virulence, which favours the expression of virulence when recessive, the Wahlund effect is expected to have no particular effect on the adaptation of nematodes to resistances.

Exploitation of FTA cartridges for the sampling, long-term storage, and DNA-based analyses of plant-parasitic nematodes.

The use of DNA-based analyses in molecular plant nematology research has dramatically increased over recent decades. Therefore, the development and adaptation of simple, robust, and cost-effective DNA purification procedures are required to address these contemporary challenges. The solid-phase-based approach developed by Flinders Technology Associates (FTA) has been shown to be a powerful technology for the preparation of DNA from different biological materials, including blood, saliva, plant tissues, and various human and plant microbial pathogens. In this work, we demonstrate, for the first time, that this FTA-based technology is a valuable, low-cost, and time-saving approach for the sampling, long-term archiving, and molecular analysis of plant-parasitic nematodes. Despite the complex structure and anatomical organization of the multicellular bodies of nematodes, we report the successful and reliable DNA-based analysis of nematode high-copy and low-copy genes using the FTA technology. This was achieved by applying nematodes to the FTA cards either in the form of a suspension of individuals, as intact or pestle-crushed nematodes, or by the direct mechanical printing of nematode-infested plant tissues. We further demonstrate that the FTA method is also suitable for the so-called "one-nematode-assay", in which the target DNA is typically analyzed from a single individual nematode. More surprisingly, a time-course experiment showed that nematode DNA can be detected specifically in the FTA-captured samples many years after initial sampling occurs. Collectively, our data clearly demonstrate the applicability and the robustness of this FTA-based approach for molecular research and diagnostics concerning phytonematodes; this research includes economically important species such as the stem nematode (Ditylenchus dipsaci), the sugar beet nematode (Heterodera schachtii), and the Northern root-knot nematode (Meloidogyne hapla).

Identification and molecular characterization of a chitin-binding protein from the beet webworm, Loxostege sticticalis L.

As the first crucial barrier in the midgut of insects, the peritrophic membrane (PM) plays an important role in preventing external invasion. PM proteins, as the major components of the PM, determine the structure and function of this membrane. A new PM protein, named LstiCBP, from the PM of Loxostege sticticalis larvae was identified using cDNA library screening. The full cDNA of LstiCBP is 2606 bp in length and contains a 2403 bp ORF that encodes an 808-amino acid preprotein with a 15-amino acid as signal peptide. The deduced protein sequence of the cDNA contains 8 cysteine-rich chitin-binding domains (CBDs). Recombinant LstiCBP was successfully expressed in BL21 cells using recombinant plasmid DNA and showed high chitin-binding activity. LstiCBP expression was detected in the midgut at both the transcriptional and translational levels; however, the biochemical and physiological functions of LstiCBP in L. sticticalis require further investigation.

USE OF GREEN MANURE CROPS AND SUGAR BEET VARIETIES TO CONTROL HETERODERA BETAE.

Although it is less studied than the white beet cyst nematode (Heterodera schachtii), the yellow beet cyst nematode (H. betae) has been found in many countries in Europe. For example in The Netherlands, France and Spain. H. betae causes yield losses on sandy soils. A high infestation can result in loss of complete plants. In The Netherlands, this nematode is especially found in the south eastern and north eastern part, where it occurs on 18% and 5% of the fields, respectively. From a project of the Dutch Sugar beet Research Institute IRS (SUSY) on factors explaining differences in sugar yield, this nematode was one of the most important factors reducing sugar yields on sandy soils. Until 2008, the only way to control H. betae was by reducing the number of host crops in the crop rotation. Host crops are crops belonging to the families of Cruciferae, Chenopodiaceae, Polygonaceae, Caryophyllaceae and Leguminosea. In order to find more control measures, research was done to investigate the host status of different green manure crops and the resistance and tolerance of different sugar beet varieties to H. betae. White mustard (Sinapis alba) and oil seed radish (Raphanus sativus spp. oleiferus) varieties resistant to H. schachtii were investigated for their resistance against H. betae. A climate room trial and a field trial with white mustard and oil seed radish were conducted in 2007 and 2008, respectively. Results show that H. betae could multiply on susceptible white mustard and susceptible oil seed radish, but not on the H. schachtii resistant varieties. In climate room trials in 2009, 2010 and 2011 and field trials in 2010, 2011 and 2012, the effect of different sugar beet varieties on the multiplication of H. betae and the effect of H. betae on yield at different infestation levels was investigated. Sugar beet varieties with resistance genes to H. schachtii (from Beta procumbens or B. maritima) were selected. Varieties with resistance genes from these sources were not totally resistant to H. betae, but limited the multiplication of this nematode in comparison with susceptible varieties considerably. Only the varieties with resistance genes from B. maritima gave higher yields in comparison with susceptible varieties. Growing these varieties was already profitable from very light infestation levels (75 eggs and larvae/100 ml soil) of H. betae. Therefore, resistant cruciferous green manure crops and resistant and tolerant sugar beet varieties are good tools for growers to control H. betae.

[Creation of transgenic sugar beet lines expressing insect pest resistance genes cry1C and cry2A].

Impact of insect pests makes a significant limitation of the sugar beet crop yield. Integration of cry-genes of Bacillus thuringiensis into plant genome is one of the promising strategies to ensure plant resistance. The aim of this work was to obtain sugar beet lines (based on the MM 1/2 line) transformed with cry2A and cry1Cgenes. We have optimized transformation protocol and direct plant let regeneration protocol from leaf explants using 1 mg/l benzylaminopurine as well as 0,25 mg/l benzylaminopurine and 0,1 mg/l indole-butyric acid. Consequently, transgenic sugar beet lines transformed with vector constructs pRD400-cry1C and pRD400-cry2A have been obtained. PCR analysis revealed integration of cry2A and cry1C into genome of transgenic lines and expression of these genes in leaf tissues was shown by reverse transcription PCR.

Synergistic interaction of CLAVATA1, CLAVATA2, and RECEPTOR-LIKE PROTEIN KINASE 2 in cyst nematode parasitism of Arabidopsis.

Plant-parasitic cyst nematodes secrete CLAVATA3 (CLV3)/ENDOSPERM SURROUNDING REGION (CLE)-like effector proteins. These proteins act as ligand mimics of plant CLE peptides and are required for successful nematode infection. Previously, we showed that the CLV2/CORYNE (CRN) heterodimer receptor complex is required for nematode CLE signaling. However, there was only a partial reduction in nematode infection when this signaling was disrupted, indicating that there might be additional nematode CLE receptors. In this study, we demonstrate that CLV1 and RECEPTOR-LIKE PROTEIN KINASE 2/TOADSTOOL2 (RPK2), two additional receptors that can transmit the CLV3 signal independent of CLV2/CRN for shoot apical meristem maintenance, also play a role in nematode CLE perception. Localization studies showed that both receptors are expressed in nematode-induced syncytia. Infection assays with clv1 and rpk2 single mutants revealed a decrease in both nematode infection and syncytium size. Significantly, further reduction in nematode infection was observed when rpk2 was combined with clv1 and clv2 mutants. Taken together, our results indicate that parallel signaling pathways involving CLV1, CLV2, and RPK2 are important for nematode parasitism.

Overexpression of the transcription factor RAP2.6 leads to enhanced callose deposition in syncytia and enhanced resistance against the beet cyst nematode Heterodera schachtii in Arabidopsis roots.

BACKGROUND: Cyst nematodes invade the roots of their host plants as second stage juveniles and induce a syncytium which is their source of nutrients throughout their life. A transcriptome analysis of syncytia induced by the beet cyst nematode Heterodera schachtii in Arabidopsis roots has shown that gene expression in the syncytium is different from that of the root with thousands of genes upregulated or downregulated. Among the downregulated genes are many which code for defense-related proteins. One gene which is strongly downregulated codes for the ethylene response transcription factor RAP2.6. The genome of Arabidopsis contains 122 ERF transcription factor genes which are involved in a variety of developmental and stress responses. RESULTS: Expression of RAP2.6 was studied with RT-PCR and a promoter::GUS line. During normal growth conditions the gene was expressed especially in roots and stems. It was inducible by Pseudomonas syringae but downregulated in syncytia from a very early time point on. Overexpression of the gene enhanced the resistance against H. schachtii which was seen by a lower number of nematodes developing on these plants as well as smaller syncytia and smaller female nematodes. A T-DNA mutant had a reduced RAP2.6 transcript level but this did not further increase the susceptibility against H. schachtii. Neither overexpression lines nor mutants had an effect on P. syringae. Overexpression of RAP2.6 led to an elevated expression of JA-responsive genes during early time points after infection by H. schachtii. Syncytia developing on overexpression lines showed enhanced deposition of callose. CONCLUSIONS: Our results showed that H. schachtii infection is accompanied by a downregulation of RAP2.6. It seems likely that the nematodes use effectors to actively downregulate the expression of this and other defense-related genes to avoid resistance responses of the host plant. Enhanced resistance of RAP2.6 overexpression lines seemed to be due to enhanced callose deposition at syncytia which might interfere with nutrient import into syncytia.

Beet cyst nematode HsSNARE1 interacts with both AtSNAP2 and AtPR1 and promotes disease in Arabidopsis.

INTRODUCTION: Plant parasitic cyst nematodes secrete a number of effectors into hosts to initiate formation of syncytia and infection causing huge yield losses. OBJECTIVES: The identified cyst nematode effectors are still limited, and the cyst nematode effectors-involved interaction mechanisms between cyst nematodes and plants remain largely unknown. METHODS: The t-SNARE domain-containing effector in beet cyst nematode (BCN) was identified by In situ hybridization and immunohistochemistry analyses. The mutant of effector gene was designed by protein structure modeling analysis. The functions of effector gene and its mutant were analyzed by genetic transformation in Arabidopsis and infection by BCN. The protein-protein interaction was analyzed by yeast two hybrid, BiFC and pulldown assays. Gene expression was assayed by quantitative real-time PCR. RESULTS: A t-SNARE domain-containing BCN HsSNARE1 was identified as an effector, and its mutant HsSNARE1-M1 carrying three mutations (E141D, A143T and -148S) that altered regional structure from random coils to α-helixes was designed and constructed. Transgenic analyses indicated that expression of HsSNARE1 significantly enhanced while expression of HsSNARE1-M1 and highly homologous HgSNARE1 remarkably suppressed BCN susceptibility of Arabidopsis. HsSNARE1 interacted with AtSNAP2 and AtPR1 via its t-SNARE domain and N-terminal, respectively, while HsSNARE1-M1/HgSNARE1 could not interact with AtPR1 but bound AtSNAP2. AtSNAP2, AtSHMT4 and AtPR1 interacted pairwise, but neither HsSNARE1 nor HsSNARE1-M1/HgSNARE1 could interact with AtSHMT4. Expression of HsSNARE1 significantly suppressed while expression of HsSNARE1-M1/HgSNARE1 considerably induced both AtSHMT4 and AtPR1 in transgenic Arabidopsis infected with BCN. Overexpression of AtPR1 significantly suppressed BCN susceptibility of Arabidopsis. CONCLUSIONS: This work identified a t-SNARE-domain containing cyst nematode effector HsSNARE1 and deciphered a molecular mode of action of the t-SNARE-domain containing cyst nematode effectors that HsSNARE1 promotes cyst nematode disease by interaction with both AtSNAP2 and AtPR1 and significant suppression of both AtSHMT4 and AtPR1, which is mediated by three structure change-causing amino acid residues.