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-β-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.

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.

Two new species of Pseudaphelenchus (Aphelenchoididae: Tylaphelenchinae) isolated from pine wood in Guangdong Province, China

Pseudaphelenchus is considered an intermediate between tylenchids and Aphelenchoididae because it has both a tylench-like bursa and aphelench-like pharynx. Three nematode populations within this genus representing two new species, P. guangdongensis n. sp. and P. paraguangdongensis n. sp., were discovered from pine trees in Guangdong province, China. P. guangdongensis n. sp. most closely resembles P. vindai due to the possession of three lines in their lateral fields, whereas P. paraguangdongensis n. sp. is most like P. yukiae because they share a four-lined field. Morphological and morphometric differences of these two new species and similar species are discussed. Additionally, molecular phylogenetic trees inferred from rRNA small subunit and D2-D3 expansion domains of the rRNA large subunit revealed that P. guangdongensis n. sp. and P. paraguangdongensis n. sp. are separated from all known Pseudaphelenchus species; moreover, all Pseudaphelenchus species comprise a highly supported monophyletic clade, which is basal to the family Aphelenchoididae.

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.

The effector MJ-10A08 of Meloidogyne javanica is required for parasitism that suppressed programmed cell death in Nicotiana benthamiana

Effectors synthesised in the pharyngeal glands are important in the successful invasion of root-knot nematodes. Meloidogyne javanica is among the nematodes that cause the most damage to various crops. In this study, an effector named MJ-10A08 of M. javanica was identified and investigated. Mj-10A08 was exclusively expressed in the dorsal pharyngeal gland cell and highly expressed in the parasitic second-juvenile stage of M. javanica. Transgenic tobaccos that over-expressed Mj-10A08 were more susceptible to M. javanica; however, host delivered RNAi of Mj-10A08 in tobacco significantly decreased the expression level of Mj-10A08 and the infection efficiency of M. javanica. Transient expression in tobacco leaves demonstrated that MJ-10A08 suppressed programmed cell death caused by BAX and Gpa2/RBP-1. Our results indicated that MJ-10A08 is implicated in the suppression of plant defence response during nematode infection and plays an important role in the parasitism of M. javanica.

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.

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 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.

Transcriptome analysis of nematode-responsive genes in two susceptible Indica rice cultivars

Meloidogyne graminicola is a major plant pathogen damaging rice. Altering a plant susceptibility gene that critically facilitates compatibility is considered one of the most effective strategies to control plant pathogens. However, no resource is currently available regarding M. graminicola susceptibility genes in Indica rice cultivars. In this study, transcriptome analysis was used to elucidate nematode-responsive genes to the two susceptible Indica rice cultivars ‘Guinongzhan’ and ‘Wushansimiao (R534)’ with distinct levels of susceptibility to M. graminicola at 3 days post-inoculation (dpi). A total of 33157 transcripts corresponded to the predicted genes in the Indica rice genome. Among these, 2062 and 1386 differentially expressed genes (DEGs) were identified in ‘Guinongzhan’ and ‘Wushansimiao (R534)’, respectively, as a result of nematode infection. Cluster analysis showed that 2184 DEGs were commonly regulated and 503 DEGs were differentially regulated in ‘Guinongzhan’ and ‘Wushansimiao (R534)’. These DEGs were involved in defence responses, the Ca2+ signal pathway, cell wall, hormone pathways, the ubiquitin proteasome system and transcription factors. In addition, candidate genes that may be involved in rice defence responses and susceptibility to M. graminicola were identified, and some of them were further validated by quantitative real-time RT-PCR. The transcription data reveal insights into the susceptible rice gene expression pattern changes upon nematode infection, and provide a novel set of candidate defence-related and susceptibility genes in Indica rice cultivars for M. graminicola.

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.

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.

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.

Arabidopsis thaliana as a model plant to study host-Meloidogyne graminicola interactions

The use of Arabidopsis thaliana as a model plant increased the rate of molecular discoveries of plant-pathogen interactions. Although Meloidogyne graminicola has a relatively broad host range, it is not known whether it can infect A. thaliana. In this study, we showed that M. graminicola is able to invade A. thaliana and complete its life cycle 12-14 days after invasion. No significant difference in the total number of nematodes inside roots of A. thaliana and rice, Oryza sativa, was found at 14 day after inoculation (dai). Significantly more galls were formed in A. thaliana roots compared to the numbers in O. sativa roots at 14 dai. Females laid egg masses on the A. thaliana root surface and a large number of hatched juveniles of the next generation were obtained from infected A. thaliana roots. In addition, the infection of M. graminicola can induce expression of A. thaliana basal defence genes, such as AtMYB51, AtWRKY11, AtPR1 and AtFRK1, at 24 h after inoculation. Therefore, A. thaliana can be considered as a suitable host to study host-M. graminicola interactions and to understand the molecular mechanisms developed by M. graminicola to infect its dicotyledonous host plants. In addition, our results also showed that a delayed development of M. graminicola occurred in A. thaliana compared to O. sativa, and a higher proportion of empty galls appeared in A. thaliana roots than in O. sativa roots, suggesting A. thaliana is a less optimal host than rice.

A new cystoid nematode, Cryphodera japonicum n. sp. (Nematoda: Heteroderidae), from the rhizosphere of Japanese Podocarpus macrophyllus

Cryphodera japonicum n. sp., detected at Ningbo port, China, from the rhizosphere of imported Japanese Podocarpus macrophyllus, is described. The new species is characterised by females with a globose body, protruding vulval lips, slightly concave anus-vulva profile, a stylet length of 37.2 (31.1-41.3) μm and a vulva-anus distance of 38.1 (34.7-44.1) μm. Males possess two lip annuli, a stylet length of 27 (22.5-30.6) μm long, three lines in lateral fields and a spicule 21.5 (19.1-23.0) μm long. Second-stage juveniles have bodies 543 (506-588) μm long, three lip annuli, a stylet 31.7 (29.2-34.5) μm long, three lines in the lateral fields, a conoid tail with a narrow rounded terminus, and a relatively long hyaline region occupying half of the tail length. Phylogenetic analyses based on the D2-D3 expansion segments of the 28S, ITS, partial 18S rRNA, and COI gene revealed the unique position of this species with other heteroderid nematodes, supporting its status as a new species of Cryphodera. The new species showed a close relationship with C. brinkmani.

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 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-β-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.

Morphological and molecular characterisation of three species of Paratylenchus Micoletzky, 1922 (Tylenchida: Paratylenchidae) from China, with a first description of the male P. rostrocaudatus

In a recent survey of plant-parasitic nematodes associated with forest in China, three species of Paratylenchus, including P. aculentus, P. leptos and P. rostrocaudatus, were found. Paratylenchus leptos and P. rostrocaudatus are new records for China and the male of P. rostrocaudatus is described for the first time. Morphological descriptions, morphometrics and light microscopic photos are provided for these three species. Molecular characterisation of these species using ribosomal RNA (rRNA) D2-D3 expansion domains of large subunit (LSU D2-D3), internal transcribed spacer (ITS) and small subunit (SSU) sequences are also given. Except for the ITS sequence of P. aculentus, other sequences were amplified for the first time. Phylogenetic relationships within the genus Paratylenchus are discussed as inferred from the analyses of LSU D2-D3, ITS and SSU.

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.

Morphological and molecular characterization of Zygotylenchus gansuensis n. sp. (Nematoda: Pratylenchinae) from China

Zygotylenchus gansuensis n. sp. is described and illustrated from the rhizosphere of jujube (Zizyphus jujuba Mill.) based on morphology and molecular analyses. This new species is characterized by a low and flattened labial region with three annuli, stylet 14.1±0.5 (13.0-14.9) μm long, deirids absent, five lateral lines in the vulval region, pharyngeal glands overlapping ventrally or ventrolaterally, V = 56.4±1.6 (54.0-60.8), indistinct spermatheca, subcylindrical tail with smooth and rounded terminus, and males absent. Molecular analyses show that the species has unique partial SSU, LSU D2D3 and ITS rRNA sequences. Phylogenetic relationships of Z. gansuensis n. sp. with other nematodes in Pratylenchinae are analysed using SSU and LSU D2D3.

The complete mitochondrial genome of Meloidogyne graminicola (Tylenchina): a unique gene arrangement and its phylogenetic implications

Meloidogyne graminicola is one of the most economically important plant parasitic-nematodes (PPNs). In the present study, we determined the complete mitochondrial (mt) DNA genome sequence of this plant pathogen. Compared with other PPNs genera, this genome (19,589 bp) is only slightly smaller than that of Pratylenchus vulnus (21,656 bp). The nucleotide composition of the whole mtDNA sequence of M. graminicola is significantly biased toward A and T, with T being the most favored nucleotide and C being the least favored. The A+T content of the entire genome is 83.51%. The mt genome of M. graminicola contains 36 genes (lacking atp8) that are transcribed in the same direction. The gene arrangement of the mt genome of M. graminicola is unique. A total of 21 out of 22 tRNAs possess a DHU loop only, while tRNASer(AGN) lacks a DHU loop. The two large noncoding regions (2,031 bp and 5,063 bp) are disrupted by tRNASer(UCN). Phylogenetic analysis based on concatenated amino acid sequences of 12 protein-coding genes support the monophylies of the three orders Rhabditida, Mermithida and Trichinellida, the suborder Rhabditina and the three infraorders Spiruromorpha, Oxyuridomorpha and Ascaridomorpha, but do not support the monophylies of the two suborders Spirurina and Tylenchina, and the three infraorders Rhabditomorpha, Panagrolaimomorpha and Tylenchomorpha. The four Tylenchomorpha species including M. graminicola, P. vulnus, H. glycines and R. similis from the superfamily Tylenchoidea are placed within a well-supported monophyletic clade, but far from the other two Tylenchomorpha species B. xylophilus and B. mucronatus of Aphelenchoidea. In the clade of Tylenchoidea, M. graminicola is sister to P. vulnus, and H. glycines is sister to R. similis, which suggests root-knot nematodes has a closer relationship to Pratylenchidae nematodes than to cyst nematodes.

The complete mitochondrial genome of Aphelenchoides besseyi (Nematoda: Aphelenchoididae), the first sequenced representative of the subfamily Aphelenchoidinae

The complete mitochondrial genome (mitogenome) ofAphelenchoides besseyiis 16 216 bp in size and has the typical organisation of nematode mitogenomes of Chromadorea, including 12 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes and the AT-rich non-coding region. The nucleotide composition of the mitogenome ofA. besseyiis AT-biased (80.0%) and the AT skew is −0.289. The most common start codon forA. besseyiis ATT. Thenad3andnad4Lgenes have an incomplete stop codon consisting of just a T and the other PCGs stop with the full stop codons. All the tRNA genes display a non-typical cloverleaf structure of mitochondrial tRNA. The AT-rich non-coding region contains ten tandem repeat units with four different regions. Phylogenetic analysis based on concatenated amino acid sequences of 12 protein-coding genes showed that three Tylenchomorpha species, includingA. besseyi,Bursaphelenchus mucronatusandB. xylophilusfrom the superfamily Aphelenchoidea, are placed within a well-supported monophyletic clade, but far from the other six Tylenchomorpha speciesMeloidogyne chitwoodi,M. graminicola,M. incognita,Pratylenchus vulnus,Heterodera glycinesandRadopholus similisof Tylenchoidea. This phylogeny suggests thatAphelenchoideshas a close relative relationship withBursaphelenchusand that the Tylenchomorpha is not monophyletic.

Molecular and biochemical characterization of the β-1,4-endoglucanase gene Mj-eng-3 in the root-knot nematode Meloidogyne javanica

This study describes the molecular and biochemical characterization of the β-1,4-endoglucanase gene (Mj-eng-3) from the root knot nematode Meloidogyne javanica. A 2156-bp genomic DNA sequence of Mj-eng-3 containing six introns was obtained. Mj-eng-3 was localized in the subventral esophageal glands of M. javanica juveniles by in situ hybridization. Real-time RT-PCR assay showed that the highest transcriptional level of Mj-eng-3 occurred in pre-parasitic second-stage juveniles, and this high expression persisted in parasitic second-stage juveniles. Recombinant MJ-ENG-3 degraded carboxymethylcellulose and optimum enzyme activity at 40°C and pH 8.0. EDTA, Mg(2+), Mn(2+), Ca(2+), Co(2+), and Cu(2+) did not affect the activity of MJ-ENG-3; however, Zn(2+) and Fe(2+) inhibited MJ-ENG-3 enzyme activity. In planta Mj-eng-3 RNAi assay displayed a reduction in the number of nematodes and galls in transgenic tobacco roots. These results suggested that MJ-ENG-3 could be secreted by M. javanica to degrade the cellulose of plant cell walls to facilitate its entry and migration during the early stages of parasitism.

First Report of Meloidogyne enterolobii on Cotton and Soybean in North Carolina, United States

Stunted cotton plants (Gossypium hirsutum L. cvs. PHY 375 WR and PHY 565 WR) from two separate fields near Goldsboro in Wayne County, North Carolina were collected by the NCDA&CS Agronomic Division nematode lab for nematode assay and identification in December 2011. The galls on cotton plants were very large in comparison with those commonly associated with Meloidogyne incognita Kofoid and White (Chitwood) infected cotton. In August 2012, the lab also received heavily galled roots of soybean (Glycine max (L.) Merr. cv. 7732) from Wayne and Johnston counties. Population densities of the 2nd-stage juveniles ranged from 150 to 3,800 per 500 cc soil. Female perineal patterns were similar to M. incognita, but PCR and DNA sequencing matched that of M. enterolobii Yang and Eisenback (4). DNA sequences of ribosomal DNA small subunit, internal transcribed spacer, large subunit domain 2 and 3, intergeneric spacer, RNA polymerase II large subunit, and histone gene H3, were found to be 100% homologous when comparing populations of M. enterolobii from North Carolina and China. Species identification was also confirmed using PCR by a species-specific SCAR primer set MK7-F/MK7-R (2). M. enterolobii Yang & Eisenback was described in 1983 from a population causing severe damage to pacara earpod tree (Enterolobium contortisiliquum (Vell.) Morong) in China (4). In 2004, M. mayaguensis Rammah & Hirschmann, a species described from Puerto Rico, was synonymized with M. enterolobii based on esterase phenotype and mitochondrial DNA sequence (3). M. enterolobii is considered to be a highly pathogenic species and has been reported from vegetables, ornamental plants, guava, and weeds in China, Africa, Central and South America, the Caribbean, and Florida in the United States (1,3,4). Of particular concern is its ability to develop on crop genotypes carrying root-knot-nematode resistance genes (Mi-1, Mh, Mir1, N, Tabasco, and Rk) in tobacco, tomato, soybean, potato, cowpea, sweet potato, and cotton. Consequently, this species was added to the European and Mediterranean Plant Protection Organization A2 Alert list in 2010. Two populations of M. enterolobii one from soybean and one from cotton were reared on tomato (Solanum lycopersicum L. var. lycopersicum) in a greenhouse setting. Eggs were extracted using NaOCl and inoculated, at a rate of 7,000 per 15-cm-diameter clay pot, into a sandy soil mixture (1:1 washed river sand and loamy sand). Tomato, peanut (Arachis hypogaea L.), cotton, watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai), pepper (Capsicum annuum L.), and root-knot-susceptible and -resistant tobacco (Nicotiana tabacum L. cvs. K326 and NC 70, respectively) were transplanted immediately into the infested soil with four replications. Root galls on the host differentials were evaluated after 90 days. Reproduction occurred on all hosts except for peanut, which is consistent with reports for M. enterolobii and M. incognita race 4 (4). Adult females from pepper plants used in the host differential test were sequenced on partial 18S and ITS1 region and confirmed to be M. enterlobii. To our knowledge, this is the first report of a natural infection of North Carolina field crops with M. enterolobii. References: (1) J. Brito et al. J. Nematol. 36:324, 2004. (2) M. S. Tigano et al. Plant Pathol. 59:1054, 2010. (3) J. Xu et al. Eur. J. Plant Pathol. 110:309, 2004. (4) B. Yang and J. D. Eisenback. J. Nematol. 15:381, 1983.

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

Heteroderafengi n. sp. is described and illustrated from bamboo (Phyllostachys pubescens Mazel) based on morphology and molecular analyses of rRNA LSU D2D3 region and ITS. This new species belongs to the Cyperi group. Cysts are characterized by prominent vulval cone with ambifenestrate, bifurcate underbridge that is thicker in middle and a 47.0 (40.0-60.0) µm long vulval slit, but without bullae. The second-stage juveniles are characterized by a 23.2 (22.0-24.0) µm long stylet with slightly projected or anteriorly flattened knobs, three incisures in lateral field, a 70.2 (62.5-77.0) µm long tail with bluntly rounded terminus and hyaline portion ca 58.9 (50.0-62.5)% of the tail length. Males are characterized by a 25.1 (24.5-26.3) µm long stylet with rounded knobs sloping posteriorly, four incisures in lateral field, a 29.8 (27.5-31.3) µm long spicule with bifurcate tip. Phylogenetic analysis shows that the species has unique D2D3 and ITS rRNA sequences and RFLP-ITS-rRNA profiles. Heteroderafengi n. sp. is closest to H. elachista in dendrograms inferred from both DNA sequences.

Heterodera hainanensis n. sp. (Nematoda: Heteroderinae) from bamboo in Hainan Province, China – a new cyst nematode in the Afenestrata group

Heterodera hainanensis n. sp. is described and illustrated from bamboo (Phyllostachys pubescens) based on morphology and molecular analyses of rRNA D2D3 region of LSU and ITS. This new species belongs to the Afenestrata group and is characterised by lemon-shaped cyst with prominent vulval cone and vulval cone without fenestration and bullae but with weak and furcate underbridge. The second-stage juvenile (J2) has two lip annuli, a 15.8-17.5 μm long stylet with rounded knobs sloping slightly posteriorly, three incisures in the lateral field and a conical tail with hyaline portion forming 52.3-71.1% of the tail length. Heterodera hainanensis n. sp. most closely resembles species in the Afenestrata group but is distinguished from these species by a number of characters, including cyst shape and size, the presence of an underbridge, vulval slit length, J2 stylet length, stylet knobs shape, incisure number and lip annule number. Molecular analysis reveals that this species has unique LSU D2D3 and ITS rRNA sequences and RFLP-ITS-rRNA profiles, and it is most closest to H. koreana in dendrograms inferred from both markers. A key to all species of the Afenestrata group is presented.

A novel effector protein, MJ-NULG1a, targeted to giant cell nuclei plays a role in Meloidogyne javanica parasitism

Secretory effector proteins expressed within the esophageal glands of root-knot nematodes (Meloidogyne spp.) are thought to play key roles in nematode invasion of host roots and in formation of feeding sites necessary for nematodes to complete their life cycle. In this study, a novel effector protein gene designated as Mj-nulg1a, which is expressed specifically within the dorsal gland of Meloidogyne javanica, was isolated through suppression subtractive hybridization. Southern blotting and BLAST search analyses showed that Mj-nulg1a is unique for Meloidogyne spp. A real-time reverse-transcriptase polymerase chain reaction assay showed that expression of Mj-nulg1a was upregulated in parasitic second-stage juveniles and declined in later parasitic stages. MJ-NULG1a contains two putative nuclear localization signals and, consistently, in planta immunolocalization analysis showed that MJ-NULG1a was localized in the nuclei of giant cells during nematode parasitism. In planta RNA interference targeting Mj-nulg1a suppressed the expression of Mj-nulg1a in nematodes and attenuated parasitism ability of M. javanica. In contrast, transgenic Arabidopsis expressing Mj-nulg1a became more susceptible to M. javanica infection than wild-type control plants. These results depict a novel nematode effector that is targeted to giant cell nuclei and plays a critical role in M. javanica parasitism.

Multiplex PCR for the simultaneous identification and detection of Meloidogyne incognita, M. enterolobii, and M. javanica using DNA extracted directly from individual galls

Meloidogyne incognita, M. enterolobii, and M. javanica are the most widespread species of root-knot nematodes in South China, affecting many economically important crops, ornamental plants, and fruit trees. In this study, one pair of Meloidogyne universal primers was designed and three pairs of species-specific primers were employed successfully to rapidly detect and identify M. incognita, M. enterolobii, and M. javanica by multiplex polymerase chain reaction (PCR) using DNA extracted from individual galls. Multiplex PCR from all M. incognita, M. enterolobii, and M. javanica isolates generated two fragments of ≈500 and 1,000, 500 and 200, and 500 and 700 bp, respectively. The 500-bp fragment is the internal positive control fragment of rDNA 28S D2/D3 resulting from the use of the universal primers. Other Meloidogyne spp. included in this study generated only one fragment of ≈500 bp in size. Using this approach, M. incognita, M. enterolobii, and M. javanica were identified and detected using DNA extracted directly from individual galls containing the Meloidogyne spp. at various stages of their life cycle. Moreover, the percentage of positive PCR amplification increased with nematode development and detection was usually easy after the late stage of the second-stage juvenile. The protocol was applied to galls from naturally infested roots and the results were found to be fast, sensitive, robust, and accurate. This present study is the first to provide a definitive diagnostic tool for M. incognita, M. enterolobii, and M. javanica using DNA extracted directly from individual galls using a one-step multiplex PCR technique.

Molecular cloning and characterization of a calreticulin cDNA from the pinewood nematode Bursaphelenchus xylophilus

The cloning and characterization of a cDNA encoding a calreticulin from the pinewood nematode Bursaphelenchus xylophilus is described herein. The full-length cDNA (Bx-crt-1) contained a 1200 bp open reading frame that could be translated to a 399 amino acid polypeptide. The deduced protein contained highly conserved regions of a calreticulin gene and had 66.2-70.1% amino acid sequence identity to other calreticulin sequences from nematodes. RNAi, RT-PCR amplification, and southern blot suggest that Bx-crt-1 may be important for the development of B. xylophilus.

First Report of Meloidogyne enterolobii on Arrowroot in China

The rhizome of arrowroot (Maranta arundinacea L.) is used as a source of edible starch in many tropical/subtropical areas. In July 2009, cultivated arrowroot plants in a field in Haikou, Hainan Province, China were observed to be exhibiting symptoms of decline, including stunting and yellowing. Roots of affected plants were found to have severe root galling similar to that caused by root-knot nematodes. Meloidogyne sp. females were dissected from the galls. Morphological characteristics of the females fit the description of M. enterolobii Yang & Eisenback (4). The perineal patterns were variable, with moderately high to high dorsal arch and mostly lacking lateral lines, but when present, the lines were not conspicuous, similar to those in the original description.(4). For further confirmation of species identity, isoenzyme patterns of malate dehydrogenase (Mdh) and esterase (Est) phenotypes were analyzed and partial sequences of mtDNA were obtained. Enzyme electrophoresis showed that the phenotypes of Mdh and Est were N1a and VS1-S1 respectively, which were consistent with those of M. enterolobii (1). Amplification and sequencing of the mtDNA between COII and the lRNA gene was accomplished with primers C2F3 (5'-GGTCAATGTTCAGAAATTTGTGG-3') and 1108 (5'-TACCTTTGACCAATCACGCT-3') (2). A DNA fragment of 705 bp was obtained and the sequence (GenBank Accession No. GQ870255) was compared with those in GenBank. A BLAST search indicated the sequence was 100% identical to the sequences of M. mayaguensis (GenBank Accession Nos. AY446969 and AY446970), a synonym of M. enterolobii (3). On the basis of these results, the root-knot nematodes isolated from arrowroot in Hainan were confirmed as M. enterolobii. This species has a high reproduction rate and a wide host range; moreover, it can induce severe galling and is able to overcome the resistance gene Mi-1 in tomato and pepper (4). M. enterolobii has become increasingly important because it has been found in many countries on diverse hosts. In China in recent years, the nematode has been reported on approximately 20 plant species belonging to five families, including Fabaceae, Cucurbitaceae, Solanaceae, Myrtaceae, and Annonaceae. To our knowledge, this is the first record of M. enterolobii parasitizing a plant (i.e., arrowroot) in the family Marantaceae in China. References: (1) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6, 1985. (2) T. O. Powers and T. S. Harris. J. Nematol. 25:1, 1993. (3) J. Xu et al. Eur. J. Plant Pathol. 110:309, 2004. (4) B. Yang and J. D. Eisenback. J. Nematol. 15:381, 1983.

Bursaphelenchus uncispicularis n. sp. (Nematoda: Parasitaphelenchidae) from Pinus yunnanensis in China

Abstract

Bursaphelenchus uncispicularis n. sp. is described and figured. The nematode was found in wilted pine Pinus yunnanensis Franchet from a single locality in Longling county, Yunnan Province, China. The new species is characterised by a relatively small stylet (11-15 μm long) with weakly developed basal swellings and lateral fields bearing four incisures. The male has relatively small, arcuate spicules with a distinct, dorsally bent, hook-like condylus, thorn-like rostrum, distinct cucullus and an ovoid terminal 'bursa' with minutely tripartite terminus. The female has a minute vulval flap and a conical tail with a relatively robust and blunt projection ca 1.2-4.5 μm long. Both sexes are of moderate body length ranging from 676-1088 μ m in the female and 552-1083 μm in the male with a slender body (a = 37-54 in the female and 36-54 in the male) and a relatively short tail (c = 26-39 in the female and 31-45 in the male). Bursaphelenchus uncispicularis n. sp. most closely resembles B. borealis, B. leoni and B. silvestris. However, the new species is easily distinguished from these three species by a number of characters including spicule size and shape, female tail shape and length, and postvulval uterine sac length.

[An IR study of ion solvation and association of lithium perchlorate in some organic solvents]

The infrared (IR) spectra of propylene carbonate (PC), gamma-butyrolactone (BL) and diethyl carbonate (DEC) in the presence of LiClO4 have been investigated. It is shown that the interactions between Li+ and these solvents occur on the oxygen atoms of the carbonyl of solvent molecules. On the other hand, spectral curve fitting for band shape of perchlorate anion shows the presence of ion association in these solutions.

Volumetric properties for the monosaccharide (D-xylose, D-arabinose, D-glucose, D-galactose)-NaCl-water systems at 298.15 K

Densities have been measured for monosaccharide (D-xylose, D-arabinose, D-glucose and D-galactose)-NaCl-water solutions at 298.15 K. These data have been used to determine the apparent molar volumes of these saccharides and NaCl in the studied solutions. Infinite-dilution apparent molar volumes for the saccharides (V0(phi,S)) in aqueous NaCl and those for NaCl (V0(phi,E)) in aqueous saccharide solutions have been evaluated, together with the standard transfer volumes of the saccharides (delta(t) V0S) from water to aqueous NaCl and of NaCl (delta(t) V0E) from water to aqueous saccharide solutions. It is shown that the delta(t) V0S and delta (t) V0E values are positive and increase with increasing co-solute molalities. Volumetric parameters indicating the interactions of NaCl with saccharides in water have been obtained, respectively, by using transfer volumes of the saccharides and NaCl, and the resulting values are in good agreement with each other within experimental error. The interactions between saccharides and NaCl are discussed in terms of the structural interaction model and the stereochemistry of the saccharide molecules in water.

Activity coefficients for NaCl-monosaccharide (D-glucose, D-galactose, D-xylose, D-arabinose)-water systems at 298.15 K

Electrochemical cells with a sodium ion selectivity electrode (Na-ISE) versus a chloride ion selectivity electrode (Cl-ISE) as a reference electrode were used to determine the activity coefficients for NaCl-monosaccharide (D-glucose, D-galactose, D-xylose, and D-arabinose) systems in water at 298.15 K. A comparison of the results thus obtained was made with those determined by another electromotive force (emf) method. It is shown that agreement is excellent. The Gibbs free energy parameters of the interactions between these sugars and NaCl in water were evaluated together with the parameter C1(CHOH, exo), indicating the interaction of the exocyclic CHOH group of saccharide molecules and NaCl. The results suggested that the interactions of these monosaccharides with NaCl are controlled mostly by the dominant conformer of their molecules in water.

Partial molar volumes of some α-amino acids in aqueous sodium acetate solutions at 308.15 K

The apparent molar volumes V(2,phi) have been determined for glycine, DL-alpha-alanine, DL-alpha-amino-n-butyric acid, DL-valine and DL-leucine in aqueous solutions of 0.5, 1.0, 1.5 and 2.0 mol kg(-1) sodium acetate by density measurements at 308.15 K. These data have been used to derive the infinite dilution apparent molar volumes V(0)(2,phi) for the amino acids in aqueous sodium acetate solutions and the standard volumes of transfer, Delta(t)V(0), of the amino acids from water to aqueous sodium acetate solutions. It has been observed that both V(0)(2,phi) and Delta(t)V(0) vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. These linear correlations have been utilized to estimate the contributions of the charged end groups (NH(3)(+), COO(-)), CH(2) group and other alkyl chains of the amino acids to V(0)(2,phi) and Delta(t)V(0). The results show that V(0)(2,phi) values for (NH(3)(+), COO(-)) groups increase with sodium acetate concentration, and those for CH(2) are almost constant over the studied sodium acetate concentration range. The transfer volume increases and the hydration number of the amino acids decreases with increasing electrolyte concentrations. These facts indicate that strong interactions occur between the ions of sodium acetate and the charged centers of the amino acids. The volumetric interaction parameters of the amino acids with sodium acetate were calculated in water. The pair interaction parameters are found to be positive and decreased with increasing alkyl chain length of the amino acids, suggesting that sodium acetate has a stronger dehydration effect on amino acids which have longer hydrophobic alkyl chains. These phenomena are discussed by means of the co-sphere overlap model.