Transcriptome Analysis of Meloidogyne javanica and the Role of a C-Type Lectin in Parasitism.

Meloidogyne javanica is one of the most widespread and economically important sedentary endoparasites. In this study, a comparative transcriptome analysis of M. javanica between pre-parasitic second-stage juveniles (Pre-J2) and parasitic juveniles (Par-J3/J4) was conducted. A total of 48,698 unigenes were obtained, of which 18,826 genes showed significant differences in expression (p < 0.05). In the differentially expressed genes (DEGs) from transcriptome data at Par-J3/J4 and Pre-J2, a large number of unigenes were annotated to the C-type lectin (CTL, Mg01965), the cathepsin L-like protease (Mi-cpl-1), the venom allergen-like protein (Mi-mps-1), Map-1 and the cellulase (endo-ß-1,4-glucanase). Among seven types of lectins found in the DEGs, there were 10 CTLs. The regulatory roles of Mj-CTL-1, Mj-CTL-2 and Mj-CTL-3 in plant immune responses involved in the parasitism of M. javanica were investigated. The results revealed that Mj-CTL-2 could suppress programmed cell death (PCD) triggered by Gpa2/RBP-1 and inhibit the flg22-stimulated ROS burst. In situ hybridization and developmental expression analyses showed that Mj-CTL-2 was specifically expressed in the subventral gland of M. javanica, and its expression was up-regulated at Pre-J2 of the nematode. In addition, in planta silencing of Mj-CTL-2 substantially increased the plant resistance to M. javanica. Moreover, yeast co-transformation and bimolecular fluorescence complementation assay showed that Mj-CTL-2 specifically interacted with the Solanum lycopersicum catalase, SlCAT2. It was demonstrated that M. javanica could suppress the innate immunity of plants through the peroxide system, thereby promoting parasitism.

A Bursaphelenchus xylophilus effector BxICD1 inducing plant cell death, concurrently contributes to nematode virulence and migration.

The migratory endoparasitic phytonematodes Bursaphelenchus xylophilus is the causal agent of pine wilt disease and causes significant economic damage to pine forests in China. Effectors play a key role in the successful parasitism of plants by phytonematodes. In this study, 210 genes obtained by transcriptomics analyses were found to be upregulated in B. xylophilus infecting Pinus massoniana that were not functionally annotated nor reported previously in B. xylophilus infecting P. thunbergii. Among these differentially expressed genes, a novel effector, BxICD1, that could induce cell death in the extracellular space of Nicotiana benthamiana was identified. BxICD1 was upregulated in the early stages of infection, as shown by RT-qPCR analyses. In situ hybridization analysis showed that BxICD1 was expressed in the esophageal gland of nematodes. The yeast signal sequence trap system indicated that BxICD1 possessed an N-terminal signal peptide with secretion functionality. Using an Agrobacterium-mediated transient expression system, it was demonstrated that the cell death-inducing activity of BxICD1 was dependent on N. benthamiana brassinosteroid-insensitive 1-associated kinase 1 (NbBAK1). Finally, BxICD1 contributed to B. xylophilus virulence and migration in host pine trees, as demonstrated by RNAi silencing assays. These findings indicate that BxICD1 both induces plant cell death and also contributes to nematode virulence and migration in P. massonian.

Meloidogyne paramali n. sp. (Nematoda: Meloidogyninae) and First Report of M. marylandi in maple and yacca tree from Japan.

Meloidogyne paramali n. sp. was detected from Japanese maple trees (Acer palmatum) from Chiba, Japan during quarantine inspections in China. This species is characterized by second-stage juveniles (J2) with short tail length 32.2 (24-36.8) µm, finely rounded to broadly pointed tail terminus with extremely short hyaline tail terminus 4.3 (3.0-4.9) µm; perineal patterns of females characterized by an oval or irregular appearance, with round and low dorsal arch, and fine and smooth striae. M. paramali n. sp. is very similar to M. mali in that the perineal pattern has fine, smooth striae and both J2 have a short tail, but it can be distinguished from the latter by perineal pattern of the female (lateral field distinct vs. indistinct), shorter J2 hyaline tail terminus (4.3 [3.0-4.9] µm vs. 8.2 [4.8-12.7] µm, and by J2 tail with finely rounded to broadly pointed tail terminus, never sharply pointed vs. finely rounded and almost pointed. The polytomous key codes of the new species are as follows: Female: A21, B2, C32, D4; Male: A21, B3, C2, D1, E2, F2; J2: A2, B23, C43, D34, E12, F34. Detailed phylogenetic analysis based on partial 18S, ITS, D2-D3 28S, and partial mtCOI sequences also confirmed it as a new species, which is very close to M. mali and M. vitis and forms molecular group VIII. M. marylandi and other Meloidogyne species detected from plants from Japan in China are also discussed.

CRISPR/Cas9-mediated mutagenesis of the susceptibility gene OsHPP04 in rice confers enhanced resistance to rice root-knot nematode.

CRISPR crops carrying a mutation in susceptibility (S) genes provide an effective strategy for controlling plant disease, because they could be 'transgene-free' and commonly have more broad-spectrum and durable type of resistance. Despite their importance, CRISPR/Cas9-mediated editing of S genes for engineering resistance to plant-parasitic nematode (PPN) disease has not been reported. In this study, we employed the CRISPR/Cas9 system to specifically induce targeted mutagenesis of the S gene rice copper metallochaperone heavy metal-associated plant protein 04 (OsHPP04), and successfully obtained genetically stable homozygous rice mutants with or without transgenic elements. These mutants confer enhanced resistance to the rice root-knot nematode (Meloidogyne graminicola), a major plant pathogenic nematode in rice agriculture. Moreover, the plant immune responses triggered by flg22, including reactive oxygen species burst, defence-related genes expression and callose deposition, were enhanced in the 'transgene-free' homozygous mutants. Analysis of rice growth and agronomic traits of two independent mutants showed that there are no obvious differences between wild-type plants and mutants. These findings suggest that OsHPP04 may be an S gene as a negative regulator of host immunity and genetic modification of S genes through the CRISPR/Cas9 technology can be used as a powerful tool to generate PPN resistant plant varieties.

A nematode effector inhibits plant immunity by preventing cytosolic free Ca2+ rise.

The Meloidogyne enterolobii effector MeTCTP is a member of the translationally controlled tumour protein (TCTP) family, involved in M. enterolobii parasitism. In this study, we found that MeTCTP forms homodimers and, in this form, binds calcium ions (Ca2+ ). At the same time, Ca2+ could induce homodimerization of MeTCTP. We further identified that MeTCTP inhibits the increase of cytosolic free Ca2+ concentration ([Ca2+ ]cyt ) in plant cells and suppresses plant immune responses. This includes suppression of reactive oxygen species burst and cell necrosis, further promoting M. enterolobii parasitism. Our results have elucidated that the effector MeTCTP can directly target Ca2+ by its homodimeric form and prevent [Ca2+ ]cyt rise in plant roots, revealing a novel mechanism utilized by plant pathogens to suppress plant immunity.

A new aphelench nematode, Basilaphelenchus brevistylus n. sp. (Aphelenchoididae: Tylaphelenchinae) from Pinus massoniana in China.

Basilaphelenchus brevistylus n. sp. was isolated from masson pine (Pinus massoniana) in Guangdong province, China. The new species is characterized by an offset lip region, short stylet (female stylet 4.5-5.5 µm and male stylet 4-5 µm long) with three elongate posteriorly directed knobs, posteriorly located metacorpal valve and lateral field composed of three lines. The female has an elongate postuterine sac and a short conical tail, uniformly narrowing toward a sharp tip, or tapering to a slightly offset mucronate tip in a few individuals. The male has a conical tail with a sharp terminal mucro, three pairs of caudal papillae, and small arcuate spicules with a bluntly rounded condylus and small pointed rostrum. B. brevistylus n. sp. can be distinguished from all described Basilaphelenchus nematodes by numerous morphological and morphometrical traits, especially the tail morphology of both sexes and stylet length. In addition, molecular phylogenetic trees inferred from rRNA small subunit and D2-D3 expansion domains of large subunit revealed that this nematode belongs to the Basilaphelenchus, and is clearly different from all the other Basilaphelsenchus species.

The Meloidogyne javanica effector Mj2G02 interferes with jasmonic acid signalling to suppress cell death and promote parasitism in Arabidopsis.

Plant-parasitic nematodes can cause devastating damage to crops. These nematodes secrete effectors that suppress the host immune responses to enhance their survival. In this study, Mj2G02, an effector from Meloidogyne javanica, is described. In situ hybridization and transcriptional analysis showed that Mj2G02 was highly expressed in the early infection stages and exclusively expressed in the nematode subventral oesophageal gland cells. In planta RNA interference targeting Mj2G02 impaired M. javanica parasitism, and Mj2G02-transgenic Arabidopsis lines displayed more susceptibility to M. javanica. Using an Agrobacterium-mediated transient expression system and plant immune response assays, we demonstrated that Mj2G02 localized in the plant cell nuclei and could suppress Gpa2/RBP-1-induced cell death. Moreover, by RNA-Seq and quantitative reverse transcription PCR analyses, we showed that Mj2G02 was capable of interfering with the host jasmonic acid (JA) signalling pathway. Multiple jasmonate ZIM-domain (JAZ) genes were significantly upregulated, whereas the JAR1 gene and four JA-responsive genes, MYC3, UPI, THI2.1, and WRKY75, were significantly downregulated. In addition, HPLC analysis showed that the endogenous jasmonoyl-isoleucine (JA-Ile) level in Mj2G02-transgenic Arabidopsis lines was significantly decreased compared to that in wildtype plants. Our results indicate that the M. javanica effector Mj2G02 suppresses the plant immune response, therefore facilitating nematode parasitism. This process is probably mediated by a JA-Ile reduction and JAZ enhancement to repress JA-responsive genes.

The Meloidogyne graminicola effector MgMO289 targets a novel copper metallochaperone to suppress immunity in rice.

Recent studies have reported that plant-parasitic nematodes facilitate their infection by suppressing plant immunity via effectors, but the inhibitory mechanisms remain poorly understood. This study found that a novel effector MgMO289 is exclusively expressed in the dorsal esophageal gland of Meloidogyne graminicola and is up-regulated at parasitic third-/fourth-stage juveniles. In planta silencing of MgMO289 substantially increased plant resistance to M. graminicola. Moreover, we found that MgMO289 interacts with a new rice copper metallochaperone heavy metal-associated plant protein 04 (OsHPP04), and that rice cytosolic COPPER/ZINC -SUPEROXIDE DISMUTASE 2 (cCu/Zn-SOD2) is the target of OsHPP04. Rice plants overexpressing OsHPP04 or MgMO289 exhibited an increased susceptibility to M. graminicola and a higher Cu/Zn-SOD activity, but lower O2•- content, when compared with wild-type plants. Meanwhile, immune response assays showed that MgMO289 could suppress host innate immunity. These findings reveal a novel pathway for a plant pathogen effector that utilizes the host O2•--scavenging system to eliminate O2•- and suppress plant immunity.

A Meloidogyne graminicola Pectate Lyase Is Involved in Virulence and Activation of Host Defense Responses.

Plant-parasitic nematodes secrete an array of cell-wall-degrading enzymes to overcome the physical barrier formed by the plant cell wall. Here, we describe a novel pectate lyase gene Mg-PEL1 from M. graminicola. Quantitative real-time PCR assay showed that the highest transcriptional expression level of Mg-PEL1 occurred in pre-parasitic second-stage juveniles, and it was still detected during the early parasitic stage. Using in situ hybridization, we showed that Mg-PEL1 was expressed exclusively within the subventral esophageal gland cells of M. graminicola. The yeast signal sequence trap system revealed that it possessed an N-terminal signal peptide with secretion function. Recombinant Mg-PEL1 exhibited hydrolytic activity toward polygalacturonic acid. Rice plants expressing RNA interference vectors targeting Mg-PEL1 showed an increased resistance to M. graminicola. In addition, using an Agrobacterium-mediated transient expression system and plant immune response assays, we demonstrated that the cell wall localization of Mg-PEL1 was required for the activation of plant defense responses, including programmed plant cell death, reactive oxygen species (ROS) accumulation and expression of defense-related genes. Taken together, our results indicated that Mg-PEL1 could enhance the pathogenicity of M. graminicola and induce plant immune responses during nematode invasion into plants or migration in plants. This provides a new insight into the function of pectate lyases in plants-nematodes interaction.

Molecular Characterization of an Emerging Root-Knot Nematode Meloidogyne enterolobii in North Carolina, USA.

An emerging threat to agriculture, Meloidogyne enterolobii Yang & Eisenback, 1983, is a tropical species and considered to be the most damaging root-knot nematode (RKN) in the world because of its wide host range, aggressiveness, and ability to overcome resistance to RKN in many crops. It was first detected in the United States on ornamental plants in Florida in 2001 but has since been identified in North Carolina, South Carolina, and Louisiana. Several thousand RKN populations were collected from North Carolina field crops, ornamental plants, and turfgrasses for species identification in the Nematode Assay Laboratory in the North Carolina Department of Agriculture & Consumer Services. From 2006 to 2019, root systems showing galling symptoms were dissected under the microscope, and females were obtained for DNA analysis. When only soil samples were submitted, the second-stage juveniles or males were used instead. Molecular characterization was performed via polymerase chain reaction with species-specific primers and DNA sequencing on the ribosomal DNA 18S-ITS1-5.8S and 28S D2/D3 and mitochondrial DNA CoxII-16S. One hundred thirty-five representative RKN populations from North Carolina were characterized and identified as M. enterolobii. Six populations from China where the species was originally described were included in this study for identity confirmation and comparison. As of December 2019, M. enterolobii has been confirmed from a limited number of fields in 11 North Carolina counties: Columbus, Craven, Greene, Harnett, Johnston, Lenoir, Nash, Pitt, Sampson, Wayne, and Wilson. Currently, M. enterolobii is the most important emerging RKN species in the United States and causes severe damage to agronomic and horticultural crops, especially sweetpotato in North Carolina.

Role of Protein Glycosylation in Host-Pathogen Interaction.

Host-pathogen interactions are fundamental to our understanding of infectious diseases. Protein glycosylation is one kind of common post-translational modification, forming glycoproteins and modulating numerous important biological processes. It also occurs in host-pathogen interaction, affecting host resistance or pathogen virulence often because glycans regulate protein conformation, activity, and stability, etc. This review summarizes various roles of different glycoproteins during the interaction, which include: host glycoproteins prevent pathogens as barriers; pathogen glycoproteins promote pathogens to attack host proteins as weapons; pathogens glycosylate proteins of the host to enhance virulence; and hosts sense pathogen glycoproteins to induce resistance. In addition, this review also intends to summarize the roles of lectin (a class of protein entangled with glycoprotein) in host-pathogen interactions, including bacterial adhesins, viral lectins or host lectins. Although these studies show the importance of protein glycosylation in host-pathogen interaction, much remains to be discovered about the interaction mechanism.

A proposal of Bursaphelenchus uncispicularis Zhuo, Li, Li, Yu & Liao, 2007 as a junior synonyms of B. yongensis Gu, Braasch, Burgermeister, Brandstetter & Zhang, 2006.

Bursaphelenchus yongensis was first reported in China, and later found in Japan and Korea. It is characterized by a relatively slim body (a = 42 and 57 for females and males, respectively). The excretory pore is located at level of median bulb, the lateral field has three lines, and a small vulval flap is present. A long post-uterine branch extends 2/3 to 3/4 of the vulva to anus distance. The conoid female tail has a 2-5 µm long mucron in the central position at the terminus. Spicules are small, condylus high and strongly dorsally bent. Subsequently Bursaphelenchus uncispicularis was described from China. Both morphological characters and morphometrics are very similar to B. yongensis, except for the number of lateral lines (4 vs 3) and male caudal papillae (7 vs 4). Re-examination of type material and a Beijing population of B. yongensis determined that B. yongensis has 7 caudal papillae instead of 4 as originally reported. It is possible that the poor condition of the type specimens of B. uncispicularis could have created difficulty in the determination of lateral line number. Unfortunately, type material of B. uncispicularis has been lost. Therefore, there is no evidence that B. uncispicularis exists. It is now established that B. yongensis is present in China, Japan and Korea with a common host species (P. thunbergii) and a common widespread vector (Cryphalus fulvus). Therefore, based on the geographic, ecological, molecular, and morphological data, we propose Bursaphelenchus uncispicularis Zhuo, Li, Li, Yu & Liao, 2007 as a junior synonym of B. yongensis Gu, Braasch, Burgermeister, Brandstetter & Zhang, 2006.

A Meloidogyne graminicola C-type lectin, Mg01965, is secreted into the host apoplast to suppress plant defence and promote parasitism.

C-type lectins (CTLs), a class of multifunctional proteins, are numerous in nematodes. One CTL gene, Mg01965, shown to be expressed in the subventral glands, especially in the second-stage juveniles of the root-knot nematode Meloidogyne graminicola, was further analysed in this study. In vitro RNA interference targeting Mg01965 in the preparasitic juveniles significantly reduced their ability to infect host plant roots. Immunolocalizations showed that Mg01965 is secreted by M. graminicola into the roots during the early parasitic stages and accumulates in the apoplast. Transient expression of Mg01965 in Nicotiana benthamiana and targeting it to the apoplast suppressed the burst of reactive oxygen species triggered by flg22. The CTL Mg01965 suppresses plant innate immunity in the host apoplast, promoting nematode parasitism in the early infection stages.

A novel Meloidogyne graminicola effector, MgMO237, interacts with multiple host defence-related proteins to manipulate plant basal immunity and promote parasitism.

Plant-parasitic nematodes can secrete effector proteins into the host tissue to facilitate their parasitism. In this study, we report a novel effector protein, MgMO237, from Meloidogyne graminicola, which is exclusively expressed within the dorsal oesophageal gland cell and markedly up-regulated in parasitic third-/fourth-stage juveniles of M. graminicola. Transient expression of MgMO237 in protoplasts from rice roots showed that MgMO237 was localized in the cytoplasm and nucleus of the host cells. Rice plants overexpressing MgMO237 showed an increased susceptibility to M. graminicola. In contrast, rice plants expressing RNA interference vectors targeting MgMO237 showed an increased resistance to M. graminicola. In addition, yeast two-hybrid and co-immunoprecipitation assays showed that MgMO237 interacted specifically with three rice endogenous proteins, i.e. 1,3-ß-glucan synthase component (OsGSC), cysteine-rich repeat secretory protein 55 (OsCRRSP55) and pathogenesis-related BetvI family protein (OsBetvI), which are all related to host defences. Moreover, MgMO237 can suppress host defence responses, including the expression of host defence-related genes, cell wall callose deposition and the burst of reactive oxygen species. These results demonstrate that the effector MgMO237 probably promotes the parasitism of M. graminicola by interacting with multiple host defence-related proteins and suppressing plant basal immunity in the later parasitic stages of nematodes.

Meloidogyne aberrans sp. nov. (Nematoda: Meloidogynidae), a new root-knot nematode parasitizing kiwifruit in China.

High infection rates of roots of wild kiwifruit (Actinidia chinensis Planch) and soil infestation by a root-knot nematode were found in Anshun, GuiZhou Province, China. Morphology, esterase phenotype and molecular analyses confirmed that this nematode was different from previously described root-knot nematodes. In this report, the species is described, illustrated and named Meloidogyne aberrans sp. nov. The new species has a unique combination of characters. A prominent posterior protuberance, round and faint perineal pattern and a medium-length stylet (13.6-15.5 µm) characterized the females. Second-stage juveniles (J2) were characterized by a smooth lip region with distinctly protruded medial lips and a depression in outline at the oral aperture, a relatively long stylet (15.9-16.8 µm), four incisures in the lateral field and a very short, even poorly defined, hyaline tail terminus (2.2-5.5 µm). More incisures (11-15) existed in the lateral field of males, and the stylet and spicules of males were 18.2-19.6 µm and 22.7-36.8 µm long respectively. Egg masses were typically produced within the roots of kiwifruit. The new species had a rare Est phenotype, S2. Phylogenetic trees inferred from SSU, LSU D2D3, ITS, and partial coxII-16S rRNA revealed that M. aberrans sp. nov. was within the Meloidogyne clade and was distinguished from all described root-knot nematodes. Moreover, from histopathological observations, M. aberrans sp. nov. induced the formation of multinucleate giant cells.

A novel Meloidogyne graminicola effector, MgGPP, is secreted into host cells and undergoes glycosylation in concert with proteolysis to suppress plant defenses and promote parasitism.

Plant pathogen effectors can recruit the host post-translational machinery to mediate their post-translational modification (PTM) and regulate their activity to facilitate parasitism, but few studies have focused on this phenomenon in the field of plant-parasitic nematodes. In this study, we show that the plant-parasitic nematode Meloidogyne graminicola has evolved a novel effector, MgGPP, that is exclusively expressed within the nematode subventral esophageal gland cells and up-regulated in the early parasitic stage of M. graminicola. The effector MgGPP plays a role in nematode parasitism. Transgenic rice lines expressing MgGPP become significantly more susceptible to M. graminicola infection than wild-type control plants, and conversely, in planta, the silencing of MgGPP through RNAi technology substantially increases the resistance of rice to M. graminicola. Significantly, we show that MgGPP is secreted into host plants and targeted to the ER, where the N-glycosylation and C-terminal proteolysis of MgGPP occur. C-terminal proteolysis promotes MgGPP to leave the ER, after which it is transported to the nucleus. In addition, N-glycosylation of MgGPP is required for suppressing the host response. The research data provide an intriguing example of in planta glycosylation in concert with proteolysis of a pathogen effector, which depict a novel mechanism by which parasitic nematodes could subjugate plant immunity and promote parasitism and may present a promising target for developing new strategies against nematode infections.

A novel Meloidogyne enterolobii effector MeTCTP promotes parasitism by suppressing programmed cell death in host plants.

Meloidogyne enterolobii is one of the most important plant-parasitic nematodes that can overcome the Mi-1 resistance gene and damage many economically important crops. Translationally controlled tumour protein (TCTP) is a multifunctional protein that exists in various eukaryotes and plays an important role in parasitism. In this study, a novel M. enterolobii TCTP effector, named MeTCTP, was identified and functionally characterized. MeTCTP was specifically expressed within the dorsal gland and was up-regulated during M. enterolobii parasitism. Transient expression of MeTCTP in protoplasts from tomato roots showed that MeTCTP was localized in the cytoplasm of the host cells. Transgenic Arabidopsis thaliana plants overexpressing MeTCTP were more susceptible to M. enterolobii infection than wild-type plants in a dose-dependent manner. By contrast, in planta RNA interference (RNAi) targeting MeTCTP suppressed the expression of MeTCTP in infecting nematodes and attenuated their parasitism. Furthermore, MeTCTP could suppress programmed cell death triggered by the pro-apoptotic protein BAX. These results demonstrate that MeTCTP is a novel plant-parasitic nematode effector that promotes parasitism, probably by suppressing programmed cell death in host plants.

Loop-Mediated Isothermal Amplification for the Detection of Tylenchulus semipenetrans in Soil.

Tylenchulus semipenetrans is an economically important plant-parasitic nematode occurring in all citrus-producing regions of the world and causing a disease called "slow decline". For the rapid detection of this nematode, a loop-mediated isothermal amplification (LAMP) assay was developed, based on the ribosomal DNA internal transcribed spacer sequence. The optimal condition for the LAMP assay was 65°C for 50 min. The LAMP products were confirmed using conventional polymerase chain reaction (PCR) and restriction analysis with the BamHI enzyme, and by adding SYBR Green I to the LAMP products for visual inspection. The LAMP assay was highly specific for the detection of T. semipenetrans populations from different geographical origins. It was also sensitive, detecting a tenth of the DNA from an individual specimen of T. semipenetrans, which was 10 times more sensitive than conventional PCR. The LAMP protocol was applied to natural citrus rhizosphere soil samples from several orchards in China and the results were fast, sensitive, robust, and accurate. This study is the first to provide a diagnostic tool for T. semipenetrans using DNA extracted directly from citrus rhizosphere soils. This LAMP assay could be used as a practical molecular tool to identify T. semipenetrans and diagnose slow decline disease, even in remote locations.

A novel nematode effector suppresses plant immunity by activating host reactive oxygen species-scavenging system.

Evidence is emerging that plant-parasitic nematodes can secrete effectors to interfere with the host immune response, but it remains unknown how these effectors can conquer host immune responses. Here, we depict a novel effector, MjTTL5, that could suppress plant immune response. Immunolocalization and transcriptional analyses showed that MjTTL5 is expressed specifically within the subventral gland of Meloidogyne javanica and up-regulated in the early parasitic stage of the nematode. Transgenic Arabidopsis lines expressing MjTTL5 were significantly more susceptible to M. javanica infection than wild-type plants, and vice versa, in planta silencing of MjTTL5 substantially increased plant resistance to M. javanica. Yeast two-hybrid, coimmunoprecipitation and bimolecular fluorescent complementation assays showed that MjTTL5 interacts specifically with Arabidopsis ferredoxin : thioredoxin reductase catalytic subunit (AtFTRc), a key component of host antioxidant system. The expression of AtFTRc is induced by the infection of M. javanica. Interaction between AtFTRc and MjTTL could drastically increase host reactive oxygen species-scavenging activity, and result in suppression of plant basal defenses and attenuation of host resistance to the nematode infection. Our results demonstrate that the host ferredoxin : thioredoxin system can be exploited cunningly by M. javanica, revealing a novel mechanism utilized by plant-parasitic nematodes to subjugate plant innate immunity and thereby promoting parasitism.

Heterodera guangdongensis n. sp. (Nematoda: Heteroderinae) from bamboo in Guangdong Province, China--a new cyst nematode in the Cyperi group.

Heterodera guangdongensis n. sp. is described from bamboo (Phyllostachys pubescens Mazel) based on morphology and molecular analyses of rRNA D2D3 expansion domains of large subunit (LSU D2D3) and internal transcribed spacer (ITS) sequences. This new species can be classified in the Cyperi group. Cysts are characterized by a prominent, ambifenestrate vulval cone with weak underbridge, a vulva-anus distance of 28.9-35.9 µm and a vulval slit of 31.1-41.0 µm, but without bullae. Females are characterized by a 25.1-27.6 µm stylet with rounded knobs sloping slightly posteriorly. Males are characterized by a 21.5-23.0 µm stylet with knobs slightly projecting or flat anteriorly, lateral field with four lines, and a 22.0-26.0 µm spicule with bifurcate tip. Second-stage juveniles are characterized by a 19.3-21.3 stylet with slightly projecting or anteriorly flattened knobs, lateral field with three lines, a 41.7-61.3 µm tail with finely rounded terminus and hyaline portion forming 43.0-57.1% of the tail length. Molecular analyses show that the species has unique D2D3 and ITS rRNA sequences and RFLP-ITS-rRNA profiles.