Salicylic acid receptors activate jasmonic acid signalling through a non-canonical pathway to promote effector-triggered immunity.

It is an apparent conundrum how plants evolved effector-triggered immunity (ETI), involving programmed cell death (PCD), as a major defence mechanism against biotrophic pathogens, because ETI-associated PCD could leave them vulnerable to necrotrophic pathogens that thrive on dead host cells. Interestingly, during ETI, the normally antagonistic defence hormones, salicylic acid (SA) and jasmonic acid (JA) associated with defence against biotrophs and necrotrophs respectively, both accumulate to high levels. In this study, we made the surprising finding that JA is a positive regulator of RPS2-mediated ETI. Early induction of JA-responsive genes and de novo JA synthesis following SA accumulation is activated through the SA receptors NPR3 and NPR4, instead of the JA receptor COI1. We provide evidence that NPR3 and NPR4 may mediate this effect by promoting degradation of the JA transcriptional repressor JAZs. This unique interplay between SA and JA offers a possible explanation of how plants can mount defence against a biotrophic pathogen without becoming vulnerable to necrotrophic pathogens

MiR-142-3p is downregulated in aggressive p53 mutant mouse models of pancreatic ductal adenocarcinoma by hypermethylation of its locus

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive disease with poor prognostic implications. This is partly due to a large proportion of PDACs carrying mutations in TP53, which impart gain-of-function characteristics that promote metastasis. There is evidence that microRNAs (miRNAs) may play a role in both gain-of-function TP53 mutations and metastasis, but this has not been fully explored in PDAC. Here we set out to identify miRNAs which are specifically dysregulated in metastatic PDAC. To achieve this, we utilised established mouse models of PDAC to profile miRNA expression in primary tumours expressing the metastasis-inducing mutant p53R172H and compared these to two control models carrying mutations, which promote tumour progression but do not induce metastasis. We show that a subset of miRNAs are dysregulated in mouse PDAC tumour tissues expressing mutant p53R172H, primary cell lines derived from mice with the same mutations and in TP53 null cells with ectopic expression of the orthologous human mutation, p53R175H. Specifically, miR-142-3p is downregulated in all of these experimental models. We found that DNA methyltransferase 1 (Dnmt1) is upregulated in tumour tissue and cell lines, which express p53R172H. Inhibition or depletion of Dnmt1 restores miR-142-3p expression. Overexpression of miR-142-3p attenuates the invasive capacity of p53R172H-expressing tumour cells. MiR-142-3p dysregulation is known to be associated with cancer progression, metastasis and the miRNA is downregulated in patients with PDAC. Here we link TP53 gain-of-function mutations to Dnmt1 expression and in turn miR-142-3p expression. Additionally, we show a correlation between expression of these genes and patient survival, suggesting that they may have potential to be therapeutic targets

Altered expression of maize PLASTOCHRON1 enhances biomass and seed yield by extending cell division duration

Maize is the highest yielding cereal crop grown worldwide for grain or silage. Here, we show that modulating the expression of the maize PLASTOCHRON1 (ZmPLA1) gene, encoding a cytochrome P450 (CYP78A1), results in increased organ growth, seedling vigour, stover biomass and seed yield. The engineered trait is robust as it improves yield in an inbred as well as in a panel of hybrids, at several locations and over multiple seasons in the field. Transcriptome studies, hormone measurements and the expression of the auxin responsive DR5(rev): mRFPer marker suggest that PLA1 may function through an increase in auxin. Detailed analysis of growth over time demonstrates that PLA1 stimulates the duration of leaf elongation by maintaining dividing cells in a proliferative, undifferentiated state for a longer period of time. The prolonged duration of growth also compensates for growth rate reduction caused by abiotic stresses

The primary cilium influences interleukin-1 beta-induced NF kappa B signalling by regulating IKK activity

AbstractThe primary cilium is an organelle acting as a master regulator of cellular signalling. We have previously shown that disruption of primary cilia assembly, through targeting intraflagellar transport, is associated with muted nitric oxide and prostaglandin responses to the inflammatory cytokine interleukin-1β (IL-1β). Here, we show that loss of the primary cilium disrupts specific molecular signalling events in cytosolic NFκB signalling. The induction of cyclooxygenase 2 (COX2) and inducible nitrous oxide synthase (iNOS) protein is abolished. Cells unable to assemble cilia exhibit unaffected activation of IκB kinase (IKK), but delayed and reduced degradation of IκB, due to diminished phosphorylation of inhibitor of kappa B (IκB) by IKK. This results in both delayed and reduced NFκB p65 nuclear translocation and nuclear transcript binding. We also demonstrate that heat shock protein 27 (hsp27), an established regulator of IKK, is localized to the ciliary axoneme and cellular levels are dramatically disrupted with loss of the primary cilium. These results suggest that the primary cilia compartment exerts influence over NFκB signalling. We propose that the cilium is a locality for regulation of the molecular events defining NFκB signalling events, tuning signalling as appropriate

Environmental and genetic regulation of mouth-form plasticity in ​Pristionchus pacificus

Phänotypische Plastizität beschreibt die Fähigkeit von Organismen, von identischem Genotyp, unterschiedliche Phänotypen als Reaktion auf Einflüsse der Umwelt zu entwickeln. Obgleich dieses Phänomen weit verbreitet ist, verbleiben die evolutionären Konsequenzen phänotypischer Veränderungen, ohne zugrunde liegender genetischer Veränderungen, ungeklärt. Eine Vielzahl von Ideen wurde unterbreitet, um die potentielle Relevanz phänotypischer Plastizität für die Evolution aufzuzeigen, jedoch bedarf die Formulierung expliziter und falsifizierbarer Hypothesen eines besseren mechanistischen Verständnisses der plastischen Entwicklung. Ein ideales Modellsystem für Studien zur phänotypischen Plastizität muss experimentelle genetische Untersuchungen erlauben, sowie Zugang zu Taxa gewährleisten, in welchen einer der alternativen Phänotypen fixiert wurde. Der Mundform-Polyphänismus der Nematoden aus der Familie der Diplogastridae erfüllt beide zuvor angeführten Kriterien. Genetisch uniforme Laborpopulationen von Pristionchus pacificus sind in der Lage zwei alternative Phänotypen, basierend auf unterschiedlichen Haltungsbedingungen, zu entwickeln. Die eurystomate (Eu) Morphe ist ein fakultativer Prädator mit weiter Mundhöhle und zwei hakenförmigen Zähnen. Bei der stenostomaten (St) Morphe hingegen, handelt es sich um einen nicht-aggressiven Mikrobivoren mit röhrenförmigem Mund und nur einem Zahn. Bisherige Studien demonstrierten eine zentrale Rolle von Pheromonen und identifizierten die Sulfatase EUD-1, die Sulfotransferase SULT-1 und den nukleären Hormonrezeptor NHR-40 als Regulatoren in der Mundformentscheidung von P. pacificus. Ziel meiner Dissertation ist es, weitere Umweltfaktoren und genetische Komponenten aufzuzeigen, welche diese Phänotypen kontrollieren. Ich entdeckte den Einfluss der Nahrungszusammensetzung und trug dazu bei, den Effekt einer Reihe von festen und flüssigen Nährmedien auf das Zahlenverhältnis der Morphen in einer Population zu identifizieren. Auf der Seite der Genetik fand ich heraus, dass eud-1 Teil eines chromosomalen Clusters von funktionell verwandten Genen ist, welcher an Supergene erinnert. Außerdem isolierte ich einen weiteren Transkriptionsfaktor, NHR-1, und identifizierte eine Reihe von gemeinsamen transkriptionalen Zielgenen von NHR-40 und NHR-1, welche möglicherweise direkt an der Produktion der alternativen Phänotypen beteiligt sind. Weiterhin beschrieb ich die Rolle von Heat Shock Proteinen in der Kanalisierung der Entwicklung alternativer Strukturen. Außerdem beteiligte ich mich an Studien, die eine genomweite Beschreibung der Chromatinzustände in P. pacificus bereitstellen und Histon-Acetylierung während der Ausprägung der Eu Morphe implizieren.Phenotypic plasticity is the ability of organisms with the same genetic complements to develop different phenotypes in response to environmental influences. This phenomenon is extremely widespread, but evolutionary consequences of phenotypic change in the absence of genetic change are currently unclear. Numerous ideas have been developed to explain the potential significance of phenotypic plasticity for evolution, but the formulation of explicit falsifiable hypotheses requires better mechanistic insight into plastic development. An ideal study system to investigate phenotypic plasticity must combine amenability to experimental genetic research and accessibility of lineages in which one of the alternative phenotypes has been fixed. Plasticity in feeding structures of diplogastrid nematodes satisfies both of these criteria. Isogenic lab populations of the species Pristionchus pacificus can develop two discrete alternative phenotypes depending on the rearing conditions. The eurystomatous (Eu) morph has a wide mouth with two hooked teeth and is a facultative predator. The stenostomatous (St) morph has a tube-like mouth with only one tooth and is a non-aggressive microbial grazer. Previous research uncovered the role of pheromones and identified the sulftase EUD-1, the sulfotransferase SULT-1 and the nuclear hormone receptor NHR-40 as regulators of mouth form decision in P. pacificus. In my thesis work, I aimed to reveal further environmental factors and genetic players controlling the phenotype. I discovered the effect of food composition and helped identify the effect of a range of solid and liquid media on the ratio between morphs in the population. On the genetic side, I found that eud-1 is part of a chromosomal cluster of functionally related genes, reminiscent of supergenes. Further, I isolated another transcription factor regulating morph decision, NHR-1, and identified a set of common transcriptional targets between NHR-40 and NHR-1, which may be the genes directly involved in making the alternative phenotypes. In addition, I elucidated the role of heat shock proteins in canalizing the development of discrete alternative morphologies. Finally, I participated in studies that provide a genome-wide description of chromatin states in P. pacificus and implicate histone acetylation in specifying the Eu morph

Interaction between the Alzheimer's peptide, beta-amyloid and lipid membrane

Alzheimer’s disease (AD) is a neurodegenerative disorder. The patho-physiological effects of amyloid beta (Aβ) may be mediated by Aβ-membrane interaction. However, the molecular mechanism of interaction between Aβ and neuronal membrane remains unknown. The aim of the study was to investigate the interaction of a toxic fragment of amyloid beta, Aβ₂₅-₃₅ with the lipid membrane model using model lipid bilayers and beta breaker peptide, KLVFF.Liquid ¹H NMR assay was used to investigate the aggregation properties of Aβ₂₅-₃₅. The sharp NMR peaks of Aβ₂₅-₃₅ appeared immediately after sample preparation and these peaks were lost after 24 hrs incubation. However, on addition of KLVFF to Aβ₂₅-₃₅, the amyloid peptide peaks remain unchanged even after long period of incubation. The data suggest that KLVFF has ability to inhibit the aggregation of Aβ₂₅-₃₅.Magic angle spinning solid state NMR were used to investigate the location and interaction of Aβ₂₅-₃₅ to lipid bilayers. NOESY cross-relaxation rates suggest that the soluble form of Aβ₂₅-₃₅ may interact predominantly with the lipid chains near glycerol region. The cholesterol molecules did not exhibit direct interaction with soluble Aβ₂₅-₃₅. However, cross relaxation rate data suggest that cholesterol may push the soluble Aβ₂₅-₃₅ towards the head region of lipid bilayers. The data indicates that soluble form of Aβ₂₅-₃₅ may enter into lipid bilayers and interact with phospholipids.²H NMR was used to analyse the effect of Aβ₂₅-₃₅ on lipid phase behaviour. M₁ analysis and methyl splitting data were used to observe the phase transitions. Aβ₂₅-₃₅ lowers the lipid phase transitions temperature in presence and absence of cholesterol. The data suggest that the insoluble form of Aβ₂₅-₃₅ may develop the lipid order (stiffness) and thus lowers the phase transition temperature. The Aβ₂₅-₃₅ plus KLVFF with cholesterol may also significantly raise the phase transition temperature and also elongate the phase transition boundaries, indicating that cholesterol molecules may enhance the lipid order parameter.In conclusion, KLVFF may stop the amyloid beta aggregation either in solution or in the lipid bilayers. Cholesterol molecules may not interact directly with amyloid beta and it may also affect the location of amyloid beta in the lipid bilayers. The results of the study may be important to understand the interactions between Aβ and lipid bilayers which may act as new therapeutic strategies for the development of new drugs for amyloid diseases

Investigation of the role of AtNOGC1, a guanylyl cyclase protein in response to abiotic and biotic stress

>Magister Scientiae - MScAgricultural production is one of the most important sectors which provide food for the growing world population which is estimated to reach 9.7 billion by 2050, thus there is a need to produce more food. Climate change, on the other hand, is negatively affecting major global crops such as maize, sorghum, wheat and barley. Environmental factors such as salinity, drought, high temperatures and pathogens affect plant production by oxidatively damaging the physiological processes in plants, leading to plant death. Poor irrigation used to combat drought result in salinasation, which is estimated to affect 50% of arable land by 2050. Plants have developed several mechanisms that protect them against stress and these include overexpression of stress responsive genes and altered signal transduction to change the expression of stress responsive genes, among others. Cyclic 3’5’ guanosine monophosphate (cGMP), a second messenger that is synthesised by guanylyl cyclase (GC), transmit signals to various cellular functions in plants during plant development, growth and response to abiotic and biotic stresses. Arabidopsis thaliana nitric oxide guanylyl cyclase 1 (AtNOGC1) is a guanylyl cyclase which upon activation by nitric oxide (NO) leads to the production of more cGMP. Cyclic GMP further activates protein kinases, ion gated channels and phosphodiesterase which mediate response to various stresses. In this project the role of AtNOGC1 was investigated in response to abiotic and biotic stresses through analysis of its evolutionary relationships, promoter, gene expression and functional analysis via the viability assays in Escherichia coli (E.coli). Phylogenetic tree, exon-intron structure and conserved motifs were analysed using the Molecular Evolutionary Genetics Analysis (MEGA V.7), Gene Structure Display Server 2.0 (GSDS 2.0), and Multiple Expectation Maximisation for Motif Elicitation (MEME) tools respectively. AtNOGC1’s gene expression was analysed by the Real-Time Quantitative Reverse Transcription Polymerase Reaction (qRT-PCR), whereas functional analysis was carried out using the cell viability (liquid and spot) assays to determine its ability to confer stress tolerance to E. coli

Carbon isotope discrimination and stomatal function in C4 grasses

Water scarcity is projected to intensify over the next fifty years due to the increasing population and changing climate. Hence, efforts are channelled towards breeding crops with improved water-use efficiency (WUE) to mitigate the negative impact of the future insecurity of food, feed, and biofuel. Leaf-level crop improvement is one key target, but to reach maximal improvements, we will need to exploit the physiological, anatomical, and biochemical diversity of grasses, the family which includes the all-important cereal crops. The success of grass productivity can be partly attributed to a finely-regulated balance between CO2 assimilation (Anet) and transpiration through highly responsive stomata, as well as the evolution of a CO2 concentrating mechanism (CCM) - the C4 cycle. The CCM of C4 photosynthesis endows C4 grasses with higher leaf-level instantaneous (WUEi) and intrinsic water use efficiency (iWUE) than C3 counterparts. In C3 plants, iWUE is directly correlated with the carbon isotope composition (δ13C) of the leaf dry matter through their separate relationships with a common parameter, the ratio of intercellular to ambient CO2 (Ci/Ca). However, leaf δ13C and iWUE in C4 plants are not consistently correlated because of the CCM and factors including post-photosynthetic carbon isotope fractionation. The two main objectives of this thesis were to (1) investigate how stomatal responses regulate leaf iWUE by exploring the physiological mechanisms underpinning the highly responsive C4 grass stomata, and (2) elucidate the impact of post-photosynthetic fractionation, particularly carbohydrate metabolism, on leaf δ13C. The two objectives serve the overall goal of better understanding the physiological factors that control leaf δ13C, iWUE and their relationship in C4 plants. I utilised C3 and C4 grasses with different photosynthetic types and C4 biochemical subtypes (NADP-ME, NAD-ME, PCK) grown under different environmental conditions. The outcomes from this study will provide fundamental knowledge and understanding of stomatal and photosynthetic regulation of iWUE in C4 grasses, allowing for the development of screening tools for breeding crops with improved iWUE

Juxta-membrane S-acylation of plant receptor-like kinases is likely fortuitous and does not necessarily impact upon function

This work was funded by UK Biotechnology and Biological Sciences Research Council Grants BB/M024911/1 and BB/M010996/1 to P.A.H.S-acylation is a common post-translational modification of membrane protein cysteine residues with many regulatory roles. S-acylation adjacent to transmembrane domains has been described in the literature as affecting diverse protein properties including turnover, trafficking and microdomain partitioning. However, all of these data are derived from mammalian and yeast systems. Here we examine the role of S-acylation adjacent to the transmembrane domain of the plant pathogen perceiving receptor-like kinase FLS2. Surprisingly, S-acylation of FLS2 adjacent to the transmembrane domain is not required for either FLS2 trafficking or signalling function. Expanding this analysis to the wider plant receptor-like kinase family we find that S-acylation adjacent to receptor-like kinase domains is common, affecting ~25% of Arabidopsis receptor-like kinases, but poorly conserved between orthologues through evolution. This suggests that S-acylation of receptor-like kinases at this site is likely the result of chance mutation leading to cysteine occurrence. As transmembrane domains followed by cysteine residues are common motifs for S-acylation to occur, and many S-acyl transferases appear to have lax substrate specificity, we propose that many receptor-like kinases are fortuitously S-acylated once chance mutation has introduced a cysteine at this site. Interestingly some receptor-like kinases show conservation of S-acylation sites between orthologues suggesting that S-acylation has come to play a role and has been positively selected for during evolution. The most notable example of this is in the ERECTA-like family where S-acylation of ERECTA adjacent to the transmembrane domain occurs in all ERECTA orthologues but not in the parental ERECTA-like clade. This suggests that ERECTA S-acylation occurred when ERECTA emerged during the evolution of angiosperms and may have contributed to the neo-functionalisation of ERECTA from ERECTA-like proteins.Publisher PDFPeer reviewe

L\'evy walks

Random walk is a fundamental concept with applications ranging from quantum physics to econometrics. Remarkably, one specific model of random walks appears to be ubiquitous across many fields as a tool to analyze transport phenomena in which the dispersal process is faster than dictated by Brownian diffusion. The L\'{e}vy walk model combines two key features, the ability to generate anomalously fast diffusion and a finite velocity of a random walker. Recent results in optics, Hamiltonian chaos, cold atom dynamics, bio-physics, and behavioral science demonstrate that this particular type of random walks provides significant insight into complex transport phenomena. This review provides a self-consistent introduction to L\'{e}vy walks, surveys their existing applications, including latest advances, and outlines further perspectives.Comment: 50 page