The nervous system of plant-parasitic nematodes and their behaviors

Nematodes are the most abundant animals on earth. The majority of nematodes are free-living which feed on bacteria and fungi in the soil. However, some nematodes are parasitic to other animals and plants and have a huge impact on human health and agriculture worldwide. The nervous system of the non-parasitic nematode Caenorhabditis elegans has been studied extensively. Based on C. elegans and a few other species, nematode nervous systems were thought to be highly conserved. However, using a comparative neuroanatomy approach, I found unexpected variation in the number and structural properties of neurons among ten species across four clades. To further study the nervous system of plant-parasitic nematodes, I investigated how the neurotransmitter serotonin regulates their behaviors. Neurotransmitters are endogenous molecules used by neurons for signal transmission. Serotonin regulates feeding and reproductive behaviors in C. elegans, but its role in plant-parasitic nematodes remains unknown. In the root-lesion nematode Pratylenchus penetrans, I detected serotonergic neurons in cells adjacent to feeding and reproductive structures. I observed that exogenous serotonin induced P. penetrans feeding and reproductive behaviors. Also, using pharmaceutical compounds that disrupt serotonin signaling, my data suggest that these neurons regulate feeding and reproductive behaviors through endogenous serotonin. The soybean cyst nematode Heterodera glycines has a distinct life cycle: both juvenile males and females lose their mobility when feeding is initiated; however, the adult males regain their mobility while females never regain mobility. As a part of a collaborative study with other lab members, I have studied the change in the mobility of H. glycines from a neuronal aspect. GABA is the most prominent inhibitory neurotransmitter in nematodes. I have constructed a map of GABAergic neurons and cloned the gene encoding the key enzyme in GABA synthesis (hg-unc-25) in H. glycines. I have used heterologous rescue in a Caenorhabditis elegans mutant and validated that HG-UNC-25 is indeed the GABA synthesizing enzyme in H. glycines. Also, I have found the sedentary stages of H. glycines is associated with a reduction of GABAergic neurons in the ventral nerve cord. Together, my research has provided evidence that the nervous systems of nematodes are not as conserved as we thought and there is a need to further investigate the nervous system. A better understanding of the nervous system of plant-parasitic nematodes may be important to understand the evolution of these parasitic nematodes. More importantly, the knowledge of the how the nervous system regulates the specific behaviors of plant-parasitic nematodes may provide insights into new control strategies

Assessing the damage potential of Pratylenchus penetrans on red raspberry cultivars

Washington State is the nation's largest producer of red raspberries for processing. The root lesion nematode, Pratylenchus penetrans, is a major constraint to the industry, shortening the productive lifespan of many plantings. Current management of P. penetrans relies upon preplant soil fumigation, but federal regulations of soil fumigants have made this practice increasingly difficult and expensive for growers. In addition, few post-plant nematode management options exist. A better understanding of the damage potential of this nematode to raspberry is necessary to guide future management recommendations. The objective of this project was to determine whether several popular raspberry cultivars in Washington State, Cascade Bounty, Chemainus, Meeker and Saanich, differ in susceptibility to P. penetrans. Field trials in existing plantings of these cultivars were established in northwest Washington. Treated plots were sprayed with the nematicides oxamyl and fosthiazate in the spring and fall of 2011 and 2012, while non-treated plots received no nematicides. Pratylenchus penetrans population densities in soil and root samples were assessed before and after each nematicide application. Pratylenchus penetrans root population densities in nematicide-treated plots were consistently v lower than those in non-treated plots at all the samplings. However, P. penetrans soil population densities in non-treated plots varied during the two year study. In summer 2011, yield of raspberry fruit in nematicide-treated plots was not significantly greater than in non-treated plots in any of the trials. In summer 2012, treated plots in the 'Chemainus' and 'Meeker' 1 trials had reduced yields along with increased fine root biomass compared to non-treated plots. In addition, in a microplot study evaluating the damage potential for P. penetrans to newly established 'Meeker' plants in a local silt loam soil and a sandy loam soil, P. penetrans had more severe damage potential to raspberry plant growth in the sandy loam soil than in the silt loam soil, but populations of P. penetrans increased faster in the silt loam soil than the sandy loam soil

Review and Meta : Analysis Psychological Conceptual Frameworks and Concepts Applied in Social Engineering

Social Engineering, which is the act of deceiving people to gain access to their personal data, has been gaining lots of attention in recent times amongst researchers and practitioners. As a consensus, IT organizations have started to manage this risk with regards to their sensitive and core corporate property via security tools and processes. Social engineering attacks are more challenging to manage since they depend on human behavior and involve taking advantage of vulnerable employees and businesses today. The understanding of the psychological concepts and frameworks set out by social engineers enable us tackle the menace. It must be tackled utilizing a combination of technology solutions and user awareness to help protect corporate information. This research provides a review and Meta - analysis for representation of these studied result of identified research works. We reflected on Psychological conceptual frameworks and concepts applied in Social Engineering attacks and conducts a paradigmatic analysis of eight researchers' work to identify the different concepts and approaches that these researchers conducted their research on. We also outline the different methodologies that aid the researchers to accomplish their work and detailed paradigmatic analysis of these eight researchers is contrasted. The Meta-Analysis enables us to identify patterns amongst the study results and shows disagreement amongst them. The final research output help researchers (readers) to understand social engineering aspect in psychological perspective and create measures to defend against these attacks. This provides a better premise for an empirical study into the area of research as well.Validerat; 20130709 (global_studentproject_submitter

GABA Immunoreactivity and Pharmacological Effects vary Among Stylet-Bearing Nematodes

Plant-parasitic nematodes conduct a series of sophisticated behaviors to complete their life cycles. Among these, locomotion behaviors, including finding the host and migrating to the feeding site, directly affect the success of parasitism. Thus, disrupting locomotion behaviors has the potential to control these parasites. γ-Aminobutyric acid (GABA) is the prominent inhibitory neurotransmitter in nematodes. GABA-immunoreactive neurons are mostly found in motor neurons, where they regulate behaviors in the model nematode C. elegans. However, the GABA system in most stylet-bearing nematodes has received little attention. Using immunohistochemistry, we found variation in the pattern of GABA-immunoreactivity among two major plant-parasites and a fungal feeder. Some of these GABA-immunoreactive neurons lack clear homologs to C. elegans. Pharmaceutical assays showed that applying GABA, its agonist, and its antagonist, can disrupt the locomotion behaviors of these nematodes, although sensitivity to a given compound varied between species. Our data suggest that the GABA system is a potential target for the control of plant-parasitic nematodes

Unexpected variation in neuroanatomy among diverse nematode species

Nematodes are considered excellent models for understanding fundamental aspects of neuron function. However, nematodes are less frequently used as models for examining the evolution of nervous systems. While the habitats and behaviors of nematodes are diverse, the neuroanatomy of nematodes is often considered highly conserved. A small number of nematode species greatly influences our understanding of nematode neurobiology. The free-living species Caenorhabditis elegans and, to a lesser extent, the mammalian gastrointestinal parasite Ascaris suum are, historically, the primary sources of knowledge regarding nematode neurobiology. Despite differences in size and habitat, C. elegans and Ascaris suum share a surprisingly similar neuroanatomy. Here, we examined species across several clades in the phylum Nematoda and show that there is a surprising degree of neuroanatomical variation both within and among nematode clades when compared to C. elegans and Ascaris. We found variation in the numbers of neurons in the ventral nerve cord and dye-filling pattern of sensory neurons. For example, we found that Pristionchus pacificus, a bacterial feeding species used for comparative developmental research, had 20% fewer ventral cord neurons compared to C. elegans. Steinernema carpocapse, an insect-parasitic nematode capable of jumping behavior, had 40% more ventral cord neurons than C. elegans. Interestingly, the non-jumping congeneric nematode, S. glaseri showed an identical number of ventral cord neurons as S. carpocapsae. There was also variability in the timing of neurodevelopment of the ventral cord with two of five species that hatch as second-stage juveniles showing delayed neurodevelopment. We also found unexpected variation in the dye-filling of sensory neurons among examined species. Again, sensory neuron dye-filling pattern did not strictly correlate with phylogeny. Our results demonstrate that variation in nematode neuroanatomy is more prevalent than previously assumed and recommend this diverse phylum for future evo-devo-neuro studies

Complete genome sequencing of nematode Aphelenchoides besseyi, an economically important pest causing rice white-tip disease

Abstract Aphelenchoides besseyi is a seed-borne plant-parasitic nematode that causes severe rice yield losses worldwide. In the present study, the A. besseyi Anhui-1 strain isolated from rice in China was sequenced with a hybrid method combining PacBio long reads and Illumina short reads, and subsequently annotated using available transcriptome references. The genome assembly consists of 166 scaffolds totaling 50.3 Mb, with an N50 of 1.262 Mb and a maximum scaffold length of 9.17 Mb. A total of 16,343 genes were annotated in the genome, with 94 gene families expanded while 70 families contracted specifically in A. besseyi. Furthermore, gene function analysis demonstrated that the genes related to drought tolerance were enriched, and cellulase genes were horizontally acquired from eukaryotic origin. Our findings provide resources to interpret the biology, evolution, ecology, and functional diversities of Aphelenchoides spp. in the light of genomics

Improving Transgenesis Efficiency and CRISPR-Associated Tools Through Codon Optimization and Native Intron Addition in Pristionchus Nematodes

A lack of appropriate molecular tools is one obstacle that prevents in-depth mechanistic studies in many organisms. Transgenesis, clustered regularly interspaced short palindromic repeats (CRISPR)-associated engineering, and related tools are fundamental in the modern life sciences, but their applications are still limited to a few model organisms. In the phylum Nematoda, transgenesis can only be performed in a handful of species other than Caenorhabditis elegans, and additionally, other species suffer from significantly lower transgenesis efficiencies. We hypothesized that this may in part be due to incompatibilities of transgenes in the recipient organisms. Therefore, we investigated the genomic features of 10 nematode species from three of the major clades representing all different lifestyles. We found that these species show drastically different codon usage bias and intron composition. With these findings, we used the species Pristionchus pacificus as a proof of concept for codon optimization and native intron addition. Indeed, we were able to significantly improve transgenesis efficiency, a principle that may be usable in other nematode species. In addition, with the improved transgenes, we developed a fluorescent co-injection marker in P. pacificus for the detection of CRISPR-edited individuals, which helps considerably to reduce associated time and costs