Permanent Feeding Site Research Articles

The Soybean Cyst Nematode Effector Cysteine Protease 1 (CPR1) Targets a Mitochondrial Soybean Branched-Chain Amino Acid Aminotransferase (GmBCAT1).

The soybean cyst nematode (SCN; Heterodera glycines) facilitates infection by secreting a repertoire of effector proteins into host cells to establish a permanent feeding site composed of a syncytium of root cells. Among the diverse proteins secreted by the nematode, we were specifically interested in identifying proteases to pursue our goal of engineering decoy substrates that elicit an immune response when cleaved by an SCN protease. We identified a cysteine protease that we named Cysteine Protease 1 (CPR1), which was predicted to be a secreted effector based on transcriptomic data obtained from SCN esophageal gland cells, presence of a signal peptide, and lack of transmembrane domains. CPR1 is conserved in all isolates of SCN sequenced to date, suggesting it is critical for virulence. Transient expression of CPR1 in Nicotiana benthamiana leaves suppressed cell death induced by a constitutively active nucleotide binding leucine-rich repeat protein, RPS5, indicating that CPR1 inhibits effector-triggered immunity. CPR1 localizes in part to the mitochondria when expressed in planta. Proximity-based labeling in transgenic soybean roots, co-immunoprecipitation, and cleavage assays identified a branched-chain amino acid aminotransferase from soybean (GmBCAT1) as a substrate of CPR1. Consistent with this, GmBCAT1 also localizes to mitochondria. Silencing of the CPR1 transcript in the nematode reduced penetration frequency in soybean roots while the expression of CPR1 in soybean roots enhanced susceptibility. Our data demonstrates that CPR1 is a conserved effector protease with a direct target in soybean roots, highlighting it as a promising candidate for decoy engineering.

Advances in Migratory Plant Endoparasitic Nematode Effectors.

Unlike sedentary plant-parasitic nematodes, migratory plant endoparasitic nematodes (MPENs) are unable to establish permanent feeding sites, and all developmental stages (except eggs) can invade and feed on plant tissues and can be easily overlooked because of the unspecific symptoms. They cause numerous economic losses in agriculture, forestry, and horticulture. In order to understand the pathogenetic mechanism of MPENs, here we describe research on functions and host targets focused on currently identified effectors from six MPENs, namely Radopholus similis, Pratylenchus spp., Ditylenchus destructor, Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Hirschmanniella oryzae. This information will provide valuable insights into understanding MPEN effectors and for future fostering advancements in plant protection.

Evaluation of Chemical-Inducible Gene Expression Systems for Beet Cyst Nematode Infection Assays in Arabidopsis thaliana.

Cyst nematodes co-opt plant developmental programs for the establishment of a permanent feeding site called a syncytium in plant roots. In recent years, the role of plant developmental genes in syncytium formation has gained much attention. One main obstacle in studying the function of development-related genes in syncytium formation is that mutation or ectopic expression of such genes can cause pleiotropic phenotypes, making it difficult to interpret nematode-related phenotypes or, in some cases, impossible to carry out infection assays due to aberrant root development. Here, we tested three commonly used inducible gene expression systems for their application in beet cyst nematode infection assays of the model plant Arabidopsis thaliana. We found that even a low amount of ethanol diminished nematode development, deeming the ethanol-based system unsuitable for use in cyst nematode infection assays, whereas treatment with estradiol or dexamethasone did not negatively affect cyst nematode viability. Dose and time course responses showed that in both systems, a relatively low dose of inducer (1 μM) is sufficient to induce high transgene expression within 24 h of treatment. Transgene expression peaked at 3 to 5 days post-induction and began to decline thereafter, providing a perfect window for inducible transgenes to interfere with syncytium establishment while minimizing any adverse effects on root development. These results indicate that both estradiol- and dexamethasone-based inducible gene expression systems are suitable for cyst nematode infection assays. The employment of such systems provides a powerful tool to investigate the function of essential plant developmental genes in syncytium formation. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Redox signalling in plant-nematode interactions: Insights into molecular crosstalk and defense mechanisms.

Plant-parasitic nematodes, specifically cyst nematodes (CNs) and root-knot nematodes (RKNs), pose significant threats to global agriculture, leading to substantial crop losses. Both CNs and RKNs induce permanent feeding sites in the root of their host plants, which then serve as their only source of nutrients throughout their lifecycle. Plants deploy reactive oxygen species (ROS) as a primary defense mechanism against nematode invasion. Notably, both CNs and RKNs have evolved sophisticated strategies to manipulate the host's redox environment to their advantage, with each employing distinct tactics to combat ROS. In this review, we have focused on the role of ROS and its scavenging network in interactions between host plants and CNs and RKNs. Overall, this review emphasizes the complex interplay between plant defense mechanism, redox signallingand nematode survival tactics, suggesting potential avenues for developing innovative nematode management strategies in agriculture.

Temporal occurrence and species composition of birds on artificial feeding sites maintained for game mammals in the Dinaric Mountains, Slovenia

Artificial feeding is a widely used management tool, but it often attracts nontarget species, including birds, to permanent feeding sites. This study used camera traps to monitor the presence of birds at selected sites used for bear management in Dinaric forest. A large number of bird species (35) were recorded, representing roughly half of all species breeding in the surrounding area. These species were grouped based on monthly and hourly presence, and corresponded to food groups, with most belonging to granivores or scavengers. Some species, such as Pigeons (Columba sp.), Raven (Corvus corax) and Buzzard (Buteo buteo), adapted their presence to the availability of food at the feeding sites, while others were not affected by this. Both Chaffinches (Fringilla coelebs) and Jays (Garrulus glandarius) frequented the feeding sites, but their temporal presence was influenced by their biology rather than by food availability. The Sparrowhawk (Accipiter nisus) also adapted its presence to food availability, and its presence was closely associated with that of the Jay. This study confirms the temporal differences in the use of feeding sites by birds and mammals, which is likely due to their different biology and past management. This can be used to make wildlife management more efficient and reduce the undesirable effects of artificial feeding.

A serological screening for potential viral pathogens among semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Finland

BackgroundReindeer herding and husbandry is a traditional and important livelihood in Fennoscandia, and about 200,000 semi-domesticated reindeer are herded in Finland. Climatic changes, leading to ice-locked winter pastures, and encroachment of pasture-land have led to changes in reindeer husbandry, increasing the extent of supplementary or full ration feeding, which has become very common in Finland. Keeping reindeer in corrals or gathering them at permanent feeding sites will increase nose-to-nose contact between animals and they may be exposed to poor hygienic conditions. This may impact the epidemiology of infectious diseases, such as viral infections. The aim of this study was to investigate Finnish semi-domesticated reindeer for exposure to viral pathogens. Blood samples were collected from 596 reindeer (358 calves, 238 adults) in 2015, from nine reindeer slaughterhouses, representing most of the reindeer herding regions in Finland. Plasma samples were investigated for antibodies against a selection of known and potential reindeer viral pathogens by using enzyme linked immunosorbent assays (ELISA).ResultsThe screening suggested that alphaherpesvirus and gammaherpesvirus (malignant catarrhal fever virus group; MCFV) were enzootic in the reindeer population, with a seroprevalence of 46.5% (range at slaughterhouse level 28.6–64.3%) and 29.0% (range 3.5–62.2%), respectively. Whereas the seroprevalence was significantly higher for alphaherpesvirus among adult reindeer (91.2%) as compared to calves (16.8%), no age difference was revealed for antibodies against gammaherpesvirus. For alphaherpesvirus, the seroprevalence in the northernmost region, having the highest animal density (animals/km2), was significantly higher (55.6%) as compared to the southernmost region (36.2%), whereas the seroprevalence pattern for gammaherpesvirus indicated the opposite, with 8.1% in the north and 50.0% in the south. Four reindeer (0.7%) had antibodies against Pestivirus, whereas no antibodies were detected against Bluetongue virus or Schmallenbergvirus.ConclusionsAlphaherpesvirus and gammaherpesvirus (MCFV) seems to be enzootic in the Finnish reindeer population, similar to other reindeer herds in Fennoscandia, whereas the exposure to Pestivirus was low compared to findings in Norway and Sweden. The ongoing changes in the reindeer herding industry necessitate knowledge on reindeer health and diseases that may impact animal welfare and health of reindeer as well as the economy of the reindeer herding industry.

Arabidopsis thaliana AtHRS1 gene is involved in the response to Heterodera schachtii infection and its overexpression hampers development of syncytia and involves a jasmonic acid-dependent mechanism

Sedentary plant parasitic nematodes have developed competences to reprogram host plant cell metabolism via sophisticated manipulation of gene expression, leading to the formation of permanent feeding sites for an unlimited source of food. Arabidopsis thaliana and the beet cyst nematode Heterodera schachtii is a good model for studying the mechanisms of compatible plant-nematode interactions and basic plant responses to nematode infection. Transcription factors are proteins that modulate plant reactions during regular development and under different biotic and abiotic stresses via direct binding to promoter regions of genes. Here, we report on the AtHRS1 gene encoding a MYB-related transcription factor belonging to the GARP family, whose expression is downregulated in syncytia, as confirmed by gene expression analysis. Constitutive overexpression of AtHRS1 disturbed the development of nematode-induced syncytia and led to a reduction in the number of developed females in transgenic A. thaliana roots. In contrast, the hrs1 mutant with decreased expression of AtHRS1 was more susceptible to cyst nematode infection. The influence of AtHRS1 on selected elements of the JA-dependent defence pathway suggests its mode of action in plant response to nematode attack. Based on these results, we suggest that the downregulation of AtHRS1 expression by nematode is important for its successful development.

Factors influencing the success of capturing European brown bears with foot snares

Abstract Management of free-ranging wildlife may include the capture of animals, with the implication that the capture process is optimized, both logistically and economically and in a way that avoids animal suffering, injury or accidental mortality. Studies targeting the optimization of trapping techniques are scarce, especially when focusing on large European mammals. Therefore, to fill this knowledge gap, we aimed to evaluate key factors that help determine brown bear capture success. This was done by analysing a complete data set from 23 years of capturing free-living Eurasian brown bears in Croatia by using Aldrich-type foot snares. Results showed significantly higher capture efficiency when traps were located at permanent feeding sites when compared to temporary feeding sites. Also, the use of a trail trap design was significantly more efficient in capturing bears than using a cubby set. Finally, results showed that trapping was more efficient when we bait the traps more frequently and when we implemented longer trap-sessions, with at least 14 days.

Arabidopsis thaliana Myb59 Gene Is Involved in the Response to Heterodera schachtii Infestation, and Its Overexpression Disturbs Regular Development of Nematode-Induced Syncytia.

Transcription factors are proteins that directly bind to regulatory sequences of genes to modulate and adjust plants’ responses to different stimuli including biotic and abiotic stresses. Sedentary plant parasitic nematodes, such as beet cyst nematode, Heterodera schachtii, have developed molecular tools to reprogram plant cell metabolism via the sophisticated manipulation of genes expression, to allow root invasion and the induction of a sequence of structural and physiological changes in plant tissues, leading to the formation of permanent feeding sites composed of modified plant cells (commonly called a syncytium). Here, we report on the AtMYB59 gene encoding putative MYB transcription factor that is downregulated in syncytia, as confirmed by RT-PCR and a promoter pMyb59::GUS activity assays. The constitutive overexpression of AtMYB59 led to the reduction in A. thaliana susceptibility, as indicated by decreased numbers of developed females, and to the disturbed development of nematode-induced syncytia. In contrast, mutant lines with a silenced expression of AtMYB59 were more susceptible to this parasite. The involvement of ABA in the modulation of AtMYB59 gene transcription appears feasible by several ABA-responsive cis regulatory elements, which were identified in silico in the gene promoter sequence, and experimental assays showed the induction of AtMYB59 transcription after ABA treatment. Based on these results, we suggest that AtMYB59 plays an important role in the successful parasitism of H. schachtii on A. thaliana roots.

Screening soybean cyst nematode effectors for their ability to suppress plant immunity.

The soybean cyst nematode (SCN), Heterodera glycines, is one of the most destructive pathogens of soybeans. SCN is an obligate and sedentary parasite that transforms host plant root cells into an elaborate permanent feeding site, a syncytium. Formation and maintenance of a viable syncytium is an absolute requirement for nematode growth and reproduction. In turn, sensing pathogen attack, plants activate defence responses and may trigger programmed cell death at the sites of infection. For successful parasitism, H. glycines must suppress these host defence responses to establish and maintain viable syncytia. Similar to other pathogens, H. glycines engages in these molecular interactions with its host via effector proteins. The goal of this study was to conduct a comprehensive screen to identify H. glycines effectors that interfere with plant immune responses. We used Nicotiana benthamiana plants infected by Pseudomonas syringae and Pseudomonas fluorescens strains. Using these pathosystems, we screened 51 H. glycines effectors to identify candidates that could inhibit effector‐triggered immunity (ETI) and/or pathogen‐associated molecular pattern (PAMP)‐triggered immunity (PTI). We identified three effectors as ETI suppressors and seven effectors as PTI suppressors. We also assessed expression modulation of plant immune marker genes as a function of these suppressors.

CCS52 and DEL1 function in root-knot nematode giant cell development in Xinjiang wild myrobalan plum (Prunus sogdiana Vassilcz).

Root-knot nematodes (RKNs) are highly invasive plant parasites that establish permanent feeding sites within the roots of the host plant. Successful establishment of the feeding site is essential for the survival of RKN. The formation and development of the feeding cell, also called giant cell, involve both cell division and endoreduplication. Here, we examined giant cell development and endoreduplication in Prunus sogdiana infected with the RKN. We found that feeding sites were established 3-5days post inoculation (dpi) and matured at 21-28dpi. The giant cells began to form 5dpi and continued to increase in size from 7 to 21dpi. The large numbers of dividing nuclei were observed in giant cells from 7 to 14dpi. However, nuclear division was rarely observed after 28days. RT-PCR and in situ hybridization analyses revealed that PsoCCS52A was abundantly expressed at 7-21dpi and the PsoCCS52A signal observed in giant cell nucleus at 7-14dpi. The PsoCCS52B is highly expressed at 14dpi, and the hybridization signal was mainly in the cytoplasm of giant cells. The PsoDEL1 expression was lowest 7-21dip, with negligible transcript detected in the giant cells. This indicates that the PsoCCS52A plays a role in the process of cell division, while the CCS52B plays a role in the development of giant cells. The PsoDEL1 plays a negative regulatory role in megakaryocyte nuclear replication. These data suggest that an increased expression of PsoCCS52A promotes nuclear division and produces a large number of polyploid nuclei, the area of giant cells and feeding sites increase, ultimately leading to the formation of galls in Prunus sogdiana.

Heterodera schachtii infection affects nitrogen metabolism in Arabidopsis thaliana

AbstractNitrogen metabolism is important for physiological processes during normal growth and development, as well as plant defence responses. Second‐stage juveniles of the cyst nematode Heterodera schachtii penetrate into the root and initiate permanent feeding sites called syncytia, from which they draw all necessary nutrients. To unravel whether the cyst nematode infestation changes nitrogen metabolism, the enzymatic activity and gene expression of nitrate (NIA) and nitrite (NIR) reductases and glutamate dehydrogenase (GDH), as well as levels of the metabolites nitrates, nitrites, and ammonium ions were estimated both locally in inoculated roots and systemically in shoots of inoculated Arabidopsis thaliana plants at 3, 7, and 15 days post‐inoculation (dpi). Moreover, gene expression of long hypocotyle 5 (HY5), a basic‐region leucine zipper (bZIP) transcription factor, was also determined, to learn more about the potential transcriptional regulation of the analysed enzymes. It was shown that the activity of nitrogen‐related enzymes and the content of metabolites fluctuated during the whole period of infection. These results were accompanied by organ‐specific and dpi‐dependent gene expression patterns. The high gene expression level of HY5 in infected roots at 7 and 15 dpi coexisted with enhanced expression of NIA1 and NIR1 at 7 dpi and NIA2 at 15 dpi. Enhanced HY5 expression level in shoots of infected plants at 15 dpi was followed by up‐regulation of NIA1 expression, suggesting that HY5 may regulate the gene expression of NIA and NIR during nematode infection. Our results indicate that changes in plant nitrogen metabolism occur during cyst nematode infection.

The effector GpRbp-1 of Globodera pallida targets a nuclear HECT E3 ubiquitin ligase to modulate gene expression in the host.

SummaryPlant‐parasitic nematodes secrete effectors that manipulate plant cell morphology and physiology to achieve host invasion and establish permanent feeding sites. Effectors from the highly expanded SPRYSEC (SPRY domain with a signal peptide for secretion) family in potato cyst nematodes have been implicated in activation and suppression of plant immunity, but the mechanisms underlying these activities remain largely unexplored. To study the host mechanisms used by SPRYSEC effectors, we identified plant targets of GpRbp‐1 from the potato cyst nematode Globodera pallida. Here, we show that GpRbp‐1 interacts in yeast and in planta with a functional potato homologue of the Homology to E6‐AP C‐Terminus (HECT)‐type ubiquitin E3 ligase UPL3, which is located in the nucleus. Potato lines lacking StUPL3 are not available, but the Arabidopsis mutant upl3‐5 displaying a reduced UPL3 expression showed a consistently small but not significant decrease in susceptibility to cyst nematodes. We observed a major impact on the root transcriptome by the lower levels of AtUPL3 in the upl3‐5 mutant, but surprisingly only in association with infections by cyst nematodes. To our knowledge, this is the first example that a HECT‐type ubiquitin E3 ligase is targeted by a pathogen effector and that a member of this class of proteins specifically regulates gene expression under biotic stress conditions. Together, our data suggest that GpRbp‐1 targets a specific component of the plant ubiquitination machinery to manipulate the stress response in host cells.

Activity profiling of barley vacuolar processing enzymes provides new insights into the plant and cyst nematode interaction.

SummaryVacuolar processing enzymes (VPEs) play an important role during regular growth and development and defence responses. Despite substantial attempts to understand the molecular basis of plant–cyst nematode interaction, the mechanism of VPEs functioning during this interaction remains unknown. The second‐stage Heterodera filipjevi juvenile penetrates host roots and induces the formation of a permanent feeding site called a syncytium. To investigate whether infection with H. filipjevi alters plant host VPEs, the studies were performed in Hordeum vulgare roots and leaves on the day of inoculation and at 7, 14 and 21 days post‐inoculation (dpi). Implementing molecular, biochemical and microscopic methods we identified reasons for modulation of barley VPE activity during interaction with H. filipjevi. Heterodera filipjevi parasitism caused a general decrease of VPE activity in infected roots, but live imaging of VPEs showed that their activity is up‐regulated in syncytia at 7 and 14 dpi and down‐regulated at 21 dpi. These findings were accompanied by tissue‐specific VPE gene expression patterns. Expression of the barley cystatin HvCPI‐4 gene was stimulated in leaves but diminished in roots upon infestation. External application of cyclotides that can be produced naturally by VPEs elicits in pre‐parasitic juveniles vesiculation of their body, enhanced formation of granules, induction of exploratory behaviour (stylet thrusts and head movements), production of reactive oxygen species (ROS) and final death by methuosis. Taken together, down‐regulation of VPE activity through nematode effectors promotes the nematode invasion rates and leads to avoidance of the induction of the plant proteolytic response and death of the invading juveniles.

Integrative diagnosis, biological observations, and histopathology of the fig cyst nematode Heteroderafici Kirjanova (1954) associated with Ficuscarica L. in southern Italy.

Morpho-biological notes and histopathology, based on LM and SEM observations, of the fig cyst nematode Heteroderafici isolated from Ficuscarica roots, collected in home and public gardens of Apulia region, southern Italy, are described and illustrated. Seventy-five localities throughout the Apulia region were sampled and one-quarter of the sampled localities had fig roots infested with H.fici, with population densities ranging from 44 to 180 cysts/100 ml of soil. All attempts to detect H.fici on ornamental Ficus spp. as well as on imported bonsai in Italy were unsuccessful. Morphometric characters of the Italian population conform to those of the type and re-description populations reported for H.fici. Molecular analysis using ITS, D2–D3 expansion domains of the 28S rRNA, and the partial 18S rRNA sequences of H.fici newly obtained in this study matched well with the corresponding sequences of H.fici present in the GenBank database. Phylogenetic trees confirmed and supported the grouping of H.fici in the Humuli group. Heteroderafici completes its embryogenic development in 14–16 days at 25 °C. Post-invasion development and maturity in the roots of F.carica seedlings is completed in 64–68 days at 25–28 °C with juveniles and adults showing different parasitic habits, being endoparasitic and semi-endoparasitic respectively. The establishment of permanent feeding sites that consist of the formation of large syncytia causes anatomical modification of vascular elements and general disorder in the root stelar structures. Syncytia structures associated with mature females showed different degrees of vacuolisation, numbers of syncytial cells, and contained nuclei and nucleoli which were constantly hypertrophied.

Lignification plays an important role on resistance to root-knot nematode ( Meloidogyne incognita ) based on contrastive analysis in peach

Abstract Root-knot nematode (RKN) is a serious global pest in peach cultivation; it establishes and maintains a permanent feeding site within plant roots. To elucidate the host response to RKN infection in peach, we conducted a comparative histological and transcriptome analysis during RKN invasion in two genotypes of peach–‘Honggengansutao’ (resistant to Meloidogyne incognita) and ‘Bailey’ (susceptible genotype). Roots of the two genotypes infested with nematodes for 0, 12, 36 and 84 h were taken as samples. Histological analysis showed that cells concentrated with RKN were lignified. Gene ontology analysis revealed a higher percentage of differential expressed genes enriched for “catalytic” and “metabolic process”. Therefore, genes with catalytic functions in lignin biosynthesis were focused on. Filtering of genes with no obvious differences compared to control revealed the resistant cultivar responded to RKN infection earlier than the susceptible one; two genes involved in upstream of lignin biosynthesis pathway were up-regulated and an additional GT-1 cis-element which can activate transcription in vivo was found in each promoter of these two genes only in the resistant cultivar. These results form a basis for understanding the mechanism of RKN resistance in peach and other plants.

Vulture mortality resulting from illegal poisoning in the southern Balkan Peninsula.

A study was carried out to determine the incidents of illegal poisoning of griffon vulture (Gyps fulvus), Egyptian vulture (Neophron percnopterus), black vulture (Aegypius monachus), and bearded vulture (Gypaetus barbatus) in the southern Balkan Peninsula between 1982 and 2017. A total of 38 poisoning cases affecting 224 vultures were analyzed to identify their causes and the primary target species for poisoning. Nine different compounds were used in these incidents and the most frequently applied were strychnine, carbamate, and organophosphoros compounds. The poison used to kill gray wolf had the most significant collateral damage to the vulture populations in comparison to the other investigated reasons. It was the primary cause of 60% of all registered vulture poisoning events in the southern Balkan Peninsula during the last 36years. Establishing permanent feeding sites for vultures in areas with wolves appears to be an effective way to minimize the risk of poisoning. There is a pressing need for the development of an appropriate conservation practice taking into consideration relationships among the main and casual target species for poisoning as an essential element in conjunction with the human activities.

Elucidation of the compatible interaction between banana and Meloidogyne incognita via high-throughput proteome profiling.

With a diverse host range, Meloidogyne incognita (root-knot nematode) is listed as one of the most economically important obligate parasites of agriculture. This nematode species establishes permanent feeding sites in plant root systems soon after infestation. A compatible host-nematode interaction triggers a cascade of morphological and physiological process disruptions of the host, leading to pathogenesis. Such disruption is reflected by altered gene expression in affected cells, detectable using molecular approaches. We employed a high-throughput proteomics approach to elucidate the events involved in a compatible banana- M. incognita interaction. This study serves as the first crucial step in developing natural banana resistance for the purpose of biological-based nematode management programme. We successfully profiled 114 Grand naine root proteins involved in the interaction with M. incognita at the 30th- and 60th- day after inoculation (dai). The abundance of proteins involved in fundamental biological processes, cellular component organisation and stress responses were significantly altered in inoculated root samples. In addition, the abundance of proteins in pathways associated with defence and giant cell maintenance in plants such as phenylpropanoid biosynthesis, glycolysis and citrate cycle were also implicated by the infestation.

Comparative transcriptome analysis of genes involved in the response of resistant and susceptible peach cultivars to nematode infection

Root-knot nematode (RKN) is among the most devastating peach pathogens, since it establishes and maintains a permanent feeding site within the plant root system. The objective of this study was to identify differentially expressed genes between two peach cultivars, one resistant and one susceptible, at 0, 0.25, 0.5, 1.5, 2.5, and 3.5 d post-inoculation (dpi) with RKN, using the Illumina HiSeq 2000 platform. Transcriptome analysis indicated that plant response was vigorous at 0.5–1.5dpi, compared with the other time points. A gene ontology analysis of the differentially expressed genes at 0.5dpi demonstrated that they were involved in metabolic and cellular processes. Filtering of genes with no obvious differences between the two cultivars revealed 11 genes associated with phytohormone metabolism that were up-regulated only in the resistant cultivar, and two genes involved in ethylene biosynthesis in the susceptible cultivar. The detailed expression pattern of the genes indicated that abscisic acid and ethylene might play an important role in signal transport during RKN infection in the resistant cultivar. Overall, this study provided a platform for further functional genomic research on peach response to RKN infection.

Arginase activity in Arabidopsis thaliana infected with Heterodera schachtii

The activity of arginase (ARGAH), which results in ornithine and urea production, is important for nitrogen metabolism in all organisms as well as for defence responses. The second‐stage juveniles of the cyst‐forming nematode Heterodera schachtii penetrate roots and induce the formation of a permanent feeding site. To determine whether infection with H. schachtii causes the induction of arginase, the expression was studied in Arabidopsis roots and shoots at the day of inoculation and at 3, 7 and 15 days post‐inoculation (dpi). Parasite infection caused a strong decrease of root arginase activity and ARGAH1 gene expression, which persisted over the entire examination period. In shoots, the mRNA expression of ARGAH2 increased at 3 and 7 dpi, but the enzymatic activity was significantly enhanced only at 3 dpi. Thus, while arginase down‐regulation occurs in roots, which is apparently due to the presence of nematode effectors, in shoots the activity is only transiently up‐regulated despite persistently high gene expression. As oxidative stress is possible during nematode infection, the activity and gene expression of glutathione reductase, a marker of the redox equilibrium, were estimated and found to be significantly enhanced at 7 dpi in shoots of infected plants. The level of proline, an amino acid known for its ability to scavenge free radicals, was increased 60‐fold. The results suggest that the disruption of redox homeostasis, as reflected by increased proline level and glutathione reductase expression and activity, accompanies changes in arginine metabolism in the shoots, indicating systemic changes induced by nematode infection.