Biology subjects

Mugford, S. T.

Publications and source records attributed to Mugford, S. T..

16 recordsLinked to original sources

bioRxiv2026

The aphid effector CathB6 suppresses EDS1-dependentimmunity and rewires MORF2-GUN1-GLK signalling tosustain host cellular homeostasis in Arabidopsis

Aphids use stylet mouthparts to probe plant tissues and deliver oral secretions into host cells, modulating immunity to establish long-term phloem feeding sites in sieve elements. This feeding behaviour make aphids efficient vectors of plant pathogens. We previously showed that Myzus persicae cathepsin B (CathB) effectors promote aphid colonization, accumulate in dynamic cytoplasmic processing bodies (p-bodies), bind the key Arabidopsis thaliana immune regulator EDS1, and recruit EDS1 together with its signalling partners PAD4 and ADR1 to p-bodies. However, the extent to which CathB effectors suppress EDS1-regulated immunity remains unclear. Here, we show that CathB6-expressing Arabidopsis lines exhibit substantial transcriptomic overlap with the eds1-2 mutant, consistent with CathB6 suppression of EDS1-dependent immunity. However, CathB6 also induces broader transcriptional reprogramming beyond that explained by loss of EDS1 function. A yeast two-hybrid screen identified the transcription factors GLK1 and GLK2, as well as several MORF proteins, as CathB6 interactors. CathB6-expressing plants recapitulated GLK- and MORF-regulated transcriptional changes, suppressing GUN1-associated activity while maintaining GLK-mediated expression of photosynthesis-associated nuclear genes (PhANGs). We found that GLKs promotes CathB6 nuclear accumulation and reduces its p-body association. TurboID proximity labelling further linked CathB6 to PhANG-associated proteins, known MORF2- and GUN1-interacting factors, p-body components, and actin-tubulin/myosin machinery, the latter being consistent with the highly dynamic behaviour of CathB6-associated p-bodies. Together, these data indicate that, beyond suppressing EDS1-mediated defenses, CathB6 interferes with the MORF2-GUN1-GLK signalling pathway, modulating plant defense responses while sustaining GLK-mediated PhANG expression to maintain cellular homeostasis during aphid attack. SIGNIFICANCE STATEMENTAphids damage crops and spread plant diseases while feeding. We discovered how a protein in aphid saliva, CathB6, helps these pests establish themselves on plants. CathB6 weakens a major immune pathway and alters communication between chloroplasts and the cell nucleus. This allows the aphid to reduce plant defences while maintaining photosynthesis and normal cell function. These findings reveal a sophisticated survival strategy and may identify ways to develop crops that are more resistant to aphids.

plant biology↗

bioRxiv2025

Whole-Genome Population Genomics Reveals Lineage Structure and Adaptive Potential of Philaenus spumarius, the Principal Vector of Xylella fastidiosa in Europe

Philaenus spumarius (L.), the meadow spittlebug, is the principal European vector of Xylella fastidiosa. This xylem-feeding insect has a broad host range, ecological plasticity, and mobility, making it an efficient vector across diverse landscapes. Yet, major gaps remain in understanding its genetic diversity, migration patterns, and local adaptation, limiting effective control of X. fastidiosa outbreaks. To address these gaps, we worked with a global network of researchers and citizen scientists to assemble a geographically and ecologically diverse collection of P. spumarius samples. We generated a chromosome-level genome assembly for P. spumarius and high-quality assemblies for four related spittlebug species, providing a robust genomic framework for evolutionary and epidemiological studies. Resequencing 430 P. spumarius individuals from across the globe uncovered boreal, temperate, and semi-arid lineages shaped by geography and climate. The lineages vary in reproductive isolation and in the degree of mito-nuclear divergence. Iberian populations grouped with an individual identified as P. tesselatus contributing to regional genetic complexity. Genomic scans identified loci under selection in Apulian populations, including signatures in sulfotransferase (SULT) genes potentially linked to behavioural plasticity, host plant specialisation, or insecticide resistance in olive-growing regions. Migration analyses indicated limited long-distance dispersal but strong local connectivity, consistent with the rapid regional spread of X. fastidiosa. Together, these findings reveal the lineage structure and adaptive potential of P. spumarius, the key vector of X. fastidiosa in Europe. They underscore the importance of targeted surveillance of locally adapted populations and provide genomic tools for monitoring vector dynamics and mitigating emerging disease risks.

evolutionary biology↗

bioRxiv2025

Effector Innovation in Genome-Reduced Phytoplasmas and Other Host-Dependent Mollicutes

Obligate host-associated bacteria with reduced genomes, such as phytoplasmas, face strong evolutionary constraints, including metabolic dependence on hosts, limited horizontal gene transfer (HGT), and frequent population bottlenecks. Despite these limitations, phytoplasmas, which are parasitic, insect-transmitted plant pathogens maintain a diverse arsenal of secreted effectors that manipulate both plant and insect hosts to promote infection and transmission. These effectors can suppress immunity and reprogram plant development, including witchs broom and leaf-like flowers, through ubiquitin-independent degradation of key transcription factors. However, how phytoplasmas diversify and maintain these effectors in the absence of frequent genetic exchange remains unclear. To address this, we analysed the effectoromes of 239 phytoplasma genomes and identified a diverse set of secreted proteins, which we designated as Phytoplasma-Associated Molecular Effectors (PhAMEs). We found that PhAMEs targeting evolutionarily conserved and structurally constrained surfaces of host proteins are widespread across phytoplasmas. These effectors adopt compact, efficient folds. They often function as molecular scaffolds with dual interaction surfaces capable of linking host proteins or integrating signalling pathways. Such scaffolding PhAMEs have evolved multiple times independently, providing clear evidence of convergent evolution. Despite severe genomic constrains imposed by genome reduction and limited HGT, gene duplications, interface variations, domain fusions, and repeat expansions have helped the shaping effector fold and diversity. While the overall effector repertoire of phytoplasmas appeared largely unique, some PhAME domains share similarities with proteins from other mollicutes and pathogens. Collectively, our findings shed light on how genome-reduced bacteria innovate molecular functions and offer insights into phytoplasma biology, effector evolution, and host-pathogen dynamics. They also lay the groundwork for protein engineering approaches aimed at discovering or designing novel biomolecules with biotechnological potential.

microbiology↗

bioRxiv2025

Aphid effector Mp10 balances immune suppression and defence activation through EDS1-dependent modulation of plant DAMP responses

O_LIDamage-associated molecular pattern (DAMP)-triggered immunity (DTI) serves as a crucial first line of defence against aphid attack, yet the mechanisms by which aphids suppress this response remain unclear. C_LIO_LIBy investigating the colonisation of Arabidopsis thaliana by the highly polyphagous peach-potato aphid (Myzus persicae), we identified cell wall-derived DAMPs, specifically oligogalacturonides (OGs), as key in inducing DTI against aphids. The OG-responsive immune components BAK1/BKK1, CPK5/CPK6, GRP3, and EDS1 collectively contribute to DTI limiting aphid colonisation. C_LIO_LIWe found that aphids limit OG production during feeding. Additionally, the salivary chemosensory protein (CSP) effector Mp10/CSP4, which is known to be delivered into the cytoplasm of plant cells early in aphid attack, inhibits OG-induced DTI. C_LIO_LIWhile Mp10 suppresses OG-induced DTI, it also interacts with EDS1-mediated defences, enhancing aphid fecundity in the absence of EDS1 but restoring OG responsiveness under attack, revealing its broader role in immune modulation and effector-driven host adaptation. C_LI

plant biology↗

bioRxiv2024

Chromosome-level Assemblies of Three Candidatus Liberibacter solanacearum Vectors: Dyspersa apicalis, Dyspersa pallida, and Trioza urticae (Hemiptera: Psylloidea)

Psyllids are major vectors of plant diseases, including Candidatus Liberibacter solanacearum (CLso), the bacterial agent associated with zebra chip disease in potatoes and carrot yellows disease in carrot. Despite their agricultural significance, there is limited knowledge on the genome structure and genetic diversity of psyllids. In this study, we provide chromosome-level genome assemblies for three psyllid species known to transmit CLso: Dyspersa apicalis (carrot psyllid), Dyspersa pallida, and Trioza urticae (nettle psyllid). As D. apicalis is recognised as the primary vector of CLso by carrot growers in Northern Europe, we also resequenced populations of this species from Finland, Norway, and Austria. Genome assemblies were constructed using PacBio HiFi and Hi-C sequencing data, yielding genome sizes of: 594.01 Mbp for D. apicalis; 587.80 Mbp for D. pallida; and 655.58 Mbp for T. urticae. Over 90% of sequences anchored into 13 pseudo-chromosomes per species. The assemblies for D. apicalis and D. pallida exhibited high completeness, capturing over 92% of conserved Hemiptera single-copy orthologues, as assessed by Benchmarking Universal Single-Copy Orthologues (BUSCO) analysis. Furthermore, we identified sequences of the primary psyllid symbiont, Candidatus Carsonella ruddii, in all three species. Comparative genomic analyses demonstrated synteny with other psyllid species. Notably, we observed significant expansions in gene families, particularly those linked to potential insecticide detoxification, within the Dyspersa lineage. Resequencing efforts also revealed the existence of multiple subpopulations of D. apicalis across Europe. These high-quality genome resources will support future research on genome evolution, insect-plant-pest interactions, and strategies for disease management. SignificancePsyllid species are significant agricultural pests, known for transmitting plant diseases like Candidatus Liberibacter solanacearum (CLso), which causes zebra chip in potatoes and carrot yellows. However, genomic data on psyllids are limited. In this study, we present high-quality, chromosome-level genome assemblies for three psyllid species: Dyspersa apicalis, Dyspersa pallida, and Trioza urticae. We generated genome assemblies with over 90% of sequences anchored to 13 pseudo-chromosomes. Comparative analyses revealed gene expansions, particularly in detoxification pathways, suggesting adaptations within the Dyspersa lineage. Population resequencing of D. apicalis across Europe uncovered genetic subpopulations. These genomes will advance understanding of psyllid biology and inform disease management strategies.

genomics↗

bioRxiv2024

Aphid effectors suppress plant immunity via recruiting defence proteins to processing bodies

Aphids are small insects that have developed specialized mouthparts and effector proteins to establish long-term relationships with plants. The peach-potato aphid, Myzus persicae, is a generalist, feeding on many plant species and capable of transmitting numerous pathogens. This study reveals how host-responsive cathepsins B (CathB) in the oral secretions of M. persicae facilitate aphid survival by modulating plant immune responses. Aphid CathB localize to processing bodies (p-bodies) and recruit key immune regulators EDS1, PAD4, and ADR1 to these bodies, suppressing plant defenses. A plant protein, Acd28.9 (Hsp20 family), counteracts this CathB activity and contributes to plant resistance to aphids. These findings highlight a novel role for p-bodies in plant immunity and uncover a plant resistance mechanism to aphid infestation.

plant biology↗

bioRxiv2024

The conserved aphid saliva chemosensory protein effector Mp10 targets plant AMSH deubiquitinases at cellular membranes to suppress pattern-triggered immunity

Chemosensory proteins (CSPs) are a conserved family present in insects and other arthropods, recognized for their critical roles in both intra- and interspecies communication. However, the functional mechanisms of these proteins remain largely unexplored. In our previous research, we identified a CSP in aphid saliva, Mp10, from the peach-potato aphid Myzus persicae, which functions as an effector protein modulating host plant immunity. Mp10 suppresses pattern recognition receptor (PRR)-triggered immunity (PTI), the first layer of plant defence, while also inducing effector-triggered immunity (ETI). In this study, we elucidate the molecular mechanisms by which Mp10 suppresses PTI. Our findings reveal that Mp10 interacts with AMSH deubiquitinase enzymes in plants, as shown by yeast two-hybrid, co-immunoprecipitation (co-IP), and FRET-FLIM assays, with these interactions predominantly localized to intracellular membranes. Mp10 was found to modulate the dynamics of membrane-bound PRR receptor kinases in plant cells. Co-IP and mass spectrometry analyses demonstrated that Mp10 and AMSH2 associate with a range of PRR kinases, PRR-associated kinases, and proteins involved in the intracellular trafficking of membrane proteins. Mp10 reduces the accumulation of these kinases at the cell surface by promoting their internalization to internal membranes, thereby dampening PTI. Supporting this, a dominant-negative catalytically inactive variant of AMSH2 also inhibits PTI. Interestingly, Mp10 orthologues from other sap-feeding hemipteran insects exhibit similar immune-suppressive activities, and our findings show that their interaction with plant AMSH proteins is conserved, indicating this immune-suppression mechanism is evolutionarily ancient.

plant biology↗

bioRxiv2022

Hybridisation has shaped a recent radiation of grass-feeding aphids

Aphids are common crop pests. These insects reproduce by facultative parthenogenesis involving several rounds of clonal reproduction interspersed with an occasional sexual cycle. Furthermore, clonal aphids give birth to live apterous or winged young that are already pregnant. Together, these qualities enable rapid population growth and have facilitated the colonisation of crops globally. In several cases so-called "super clones" have come to dominate agricultural systems. However, the extent to which the sexual stage of the aphid life cycle has shaped global pest populations has remained largely unclear, as have the origins of successful lineages. Here, we used chromosome-scale genome assemblies to disentangle the evolution of two of the most significant global pests of cereals - the English (Sitobion avenae) and Indian (Sitobion miscanthi) grain aphids. We found that genome-wide divergence between S. avenae and S. miscanthi is low and that S. avenae sensu stricto is part of a larger cryptic species complex that includes multiple diverged S. miscanthi lineages. Moreover, comparison of haplotype-resolved assemblies reveals that the S. miscanthi isolate used for genome sequencing is likely a hybrid, with one of its diploid genome copies being closely related to S. avenae ([~]0.5% divergence) and the second being substantially more divergent (> 1%). Analyses of genotyping-by-sequencing (GBS) data of grain aphids from the UK and China revealed that S. avenae and S. miscanthi are part of a species complex with many highly differentiated lineages that predate the origins of agriculture. The complex consists of hybrid lineages that display a tangled history of hybridisation and genetic introgression. These data demonstrate that hybridisation has substantially contributed to grain aphid diversity, and hence, to the evolutionary potential of this important pest species.

evolutionary biology↗

bioRxiv2021

Plant pathogens convergently evolved to counteract redundant nodes of an NLR immune receptor network

In plants, NLR (nucleotide-binding domain and leucine-rich repeat-containing) proteins can form receptor networks to confer hypersensitive cell death and innate immunity. One class of NLRs, known as NRCs (NLR required for cell death), are central nodes in a complex network that protects against multiple pathogens and comprises up to half of the NLRome of solanaceous plants. Given the prevalence of this NLR network, we hypothesized that pathogens convergently evolved to secrete effectors that target NRC activities. To test this, we screened a library of 167 bacterial, oomycete, nematode and aphid effectors for their capacity to suppress the cell death response triggered by the NRC-dependent disease resistance proteins Prf and Rpi-blb2. Among five of the identified suppressors, one cyst nematode protein and one oomycete protein suppress the activity of autoimmune mutants of NRC2 and NRC3, but not NRC4, indicating that they specifically counteract a subset of NRC proteins independently of their sensor NLR partners. Whereas the cyst nematode effector SPRYSEC15 binds the nucleotide-binding domain of NRC2 and NRC3, the oomycete effector AVRcap1b suppresses the response of these NRCs via the membrane trafficking-associated protein NbTOL9a (Target of Myb 1-like protein 9a). We conclude that plant pathogens have evolved to counteract central nodes of the NRC immune receptor network through different mechanisms. Coevolution with pathogen effectors may have driven NRC diversification into functionally redundant nodes in a massively expanded NLR network.

plant biology↗

bioRxiv2020

A chromosome-level genome assembly of the woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae)

Woolly apple aphid (WAA, Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae), is a major pest of apple trees (Malus domestica, order Rosales) and is critical to the economics of the apple industry in most parts of the world. Here, we generated a chromosome-level genome assembly of WAA - representing the first genome sequence from the aphid subfamily Eriosomatinae - using a combination of 10X Genomics linked-reads and in vivo Hi-C data. The final genome assembly is 327 Mb, with 91% of the assembled sequences anchored into six chromosomes. The contig and scaffold N50 values are 158 kb and 71 Mb, respectively, and we predicted a total of 28,186 protein-coding genes. The assembly is highly complete, including 97% of conserved arthropod single-copy orthologues based on BUSCO analysis. Phylogenomic analysis of WAA and nine previously published aphid genomes, spanning four aphid tribes and three subfamilies, reveals that the tribe Eriosomatini (represented by WAA) is recovered as a sister group to Aphidini + Macrosiphini (subfamily Aphidinae). We identified syntenic blocks of genes between our WAA assembly and the genomes of other aphid species and find that two WAA chromosomes (El5 and El6) map to the conserved Macrosiphini and Aphidini X chromosome. Our high-quality WAA genome assembly and annotation provides a valuable resource for research in a broad range of areas such as comparative and population genomics, insect-plant interactions and pest resistance management.

genomics↗

bioRxiv2020

Genome sequence of the banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) and its symbionts

The banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae), is a major pest of cultivated bananas (Musa spp., order Zingiberales), primarily due to its role as a vector of Banana bunchy top virus (BBTV), the most severe viral disease of banana worldwide. Here, we generated a highly complete genome assembly of P. nigronervosa using a single PCR-free Illumina sequencing library. Using the same sequence data, we also generated complete genome assemblies of the P. nigronervosa symbiotic bacteria Buchnera aphidicola and Wolbachia. To improve our initial assembly of P. nigronervos a we developed a k-mer based deduplication pipeline to remove genomic scaffolds derived from the assembly of haplotigs (allelic variants assembled as separate scaffolds). To demonstrate the usefulness of this pipeline, we applied it to the recently generated assembly of the aphid Myzus cerasi, reducing the duplication of conserved BUSCO genes by 25%. Phylogenomic analysis of P. nigronervos a, our improved M. cerasi assembly, and seven previously published aphid genomes, spanning three aphid tribes and two subfamilies, reveals that P. nigronervos a falls within the tribe Macrosiphini, but is an outgroup to other Macrosiphini sequenced so far. As such, the genomic resources reported here will be useful for understanding both the evolution of Macrosphini and for the study of P. nigronervosa. Furthermore, our approach using low cost, high-quality, Illumina short-reads to generate complete genome assemblies of understudied aphid species will help to fill in genomic black spots in the diverse aphid tree of life.

genomics↗

bioRxiv2020

Chromosome-scale genome assemblies of aphids reveal extensively rearranged autosomes and long-term conservation of the X chromosome

Large-scale chromosome rearrangements are arguably the most dramatic type of mutations, often leading to rapid evolution and speciation. However, chromosome dynamics have only been studied at the sequence level in a small number of model systems. In insects, Diptera (flies and mosquitoes) and Lepidoptera (butterflies and moths) have high levels of chromosome conservation. Whether this truly reflects the diversity of insect genome evolution is questionable given that many species exhibit rapid karyotype evolution. Here, we investigate chromosome evolution in aphids - an important group of hemipteran plant pests - using newly generated chromosome-scale genome assemblies of the green peach aphid (Myzus persicae) and the pea aphid (Acyrthosiphon pisum), and a previously published chromosome-scale assembly of the corn-leaf aphid (Rhopalosiphum maidis). We find that aphid autosomes have undergone dramatic reorganisation over the last 30 million years, to the extent that chromosome homology cannot be determined between aphids from the tribes Macrosiphini (M. persicae and A. pisum) and Aphidini (R. maidis). In contrast, gene content of the aphid sex (X) chromosome remained unchanged despite rapid sequence evolution, low gene expression and high transposable element load. To test whether rapid evolution of genome structure is a hallmark of Hemiptera, we compared our aphid assemblies to chromosome-level assemblies of two blood-feeding Hemiptera (Rhodnius prolixus and Triatoma rubrofasciata). Despite being more diverged, the blood-feeding hemipterans have conserved synteny and we detect only two chromosome fusion or fission events. The exceptional rate of structural evolution of aphid autosomes renders them an important emerging model system for studying the role of large-scale genome rearrangements in evolution.

genomics↗

bioRxiv2019

An aphid host-responsive RNA transcript that migrates systemically in plants promotes aphid reproduction

Aphids are sap-feeding insects that colonize a broad range of plant species and often cause feeding damage and transmit plant pathogens, including bacteria, viruses and viroids. These insects feed from the plant vascular tissue, predominantly the phloem. However, it remains largely unknown how aphids, and other sap-feeding insects, establish intimate long-term interactions with plants. To identify aphid virulence factors, we took advantage of the ability of the green peach aphid Myzus persicae to colonize divergent plant species. We found that a M. persicae clone of near-identical females establishes stable colonies on nine plant species of five representative plant eudicot and monocot families that span the angiosperm phylogeny. Members of the novel aphid Ya family are differentially expressed in aphids on the nine plant species, are co-regulated and organized as tandem repeats in aphid genomes. Interestingly, aphids translocate Ya transcripts into plants and some transcripts migrate systemically within several plant species. RNAi-mediated knock down of Ya genes reduces M. persicae fecundity and M. persicae produces more progeny on transgenic plants that heterologously produce one of the systemically migrating Ya transcripts as a long non-coding (lnc)RNA. Taken together, our work led to the discovery of a new host-responsive aphid gene family that operate as virulence factors. Transcripts of this family translocate into plants, including a lncRNA that migrates systemically and promotes aphid reproduction.\n\nSignificance StatementThe green peach aphid Myzus persicae causes yield losses of a diverse range of economically important crops primarily as a vector of more than 100 different plant pathogens. We found that a single genotype of M. persicae is able to colonize nine plant species, including diverse dicots and maize, indicating that this aphid is truly polyphagous. Members of a new aphid Ya family undergoes coordinated expression changes in M. persicae depending on the plant species. The aphids translocate Ya transcripts into plants during feeding and these RNAs migrate to systemic leaves. Moreover, heterologous in planta expression of M. persicae Ya1 as a long non-coding RNA promotes aphid reproduction. Our findings indicate that cross kingdom deployment of RNA is more common than thought.

genomics↗

bioRxiv2018

Sex-specific changes in the aphid DNA methylation landscape

Aphids present an ideal system to study epigenetics as they can produce diverse, but genetically identical, morphs in response to environmental stimuli. Here, using whole genome bisulphite sequencing and transcriptome sequencing of the green peach aphid (Myzus persicae), we present the first detailed analysis of cytosine methylation in an aphid and investigate differences in the methylation and transcriptional landscapes of male and asexual female morphs. We find that methylation primarily occurs in a CG dinucleotide (CpG) context and that exons are highly enriched for methylated CpGs, particularly at the 3 end of genes. Methylation is positively associated with gene expression, and methylated genes are more stably expressed than un-methylated genes. Male and asexual female morphs have distinct methylation profiles. Strikingly, these profiles are divergent between the sex chromosome and the autosomes; autosomal genes are hypo-methylated in males compared to asexual females, whereas genes belonging to the sex chromosome, which is haploid in males, are hyper-methylated. Overall, we find correlated changes in methylation and gene expression between males and asexual females, and this correlation is particularly strong for genes located on the sex chromosome. Our results suggest that differential methylation of sex-biased genes plays a role in M. persicae sexual differentiation.

genomics↗

bioRxiv2017

Chemosensory proteins in the CSP4 clade evolved as plant immunity suppressors before two suborders of plant-feeding hemipteran insects diverged

Chemosensory proteins (CSPs) are small globular proteins with hydrophobic binding pockets that have a role in detection of chemicals, regulation of development and growth and host seeking behaviour and feeding of arthropods. Here, we show that a CSP has evolved to modulate plant immune responses. Firstly, we found that the green peach aphid Myzus persicae CSP Mp10, which is delivered into the cytoplasm of plant cells, suppresses the reactive oxygen species (ROS) bursts to both aphid and bacterial elicitors in Arabidopsis thaliana and Nicotiana benthamiana. Aphid RNA interference studies demonstrated that Mp10 modulates the first layer of the plant defence response, specifically the BAK1 pathway. We identified Mp10 homologs in diverse plant-sucking insect species, including aphids, whiteflies, psyllids and leafhoppers, but not in other insect species, including blood-feeding hemipteran insects. We found that Mp10 homologs from other splant-sucking insect species are also capable of suppressing plant ROS. Together, these data and phylogenetic analyses provides evidence that an ancestral Mp10-like sequence acquired plant ROS suppression activity before the divergence of plant-sucking insect species over 250 million years ago.\n\nSignificanceAphids, whiteflies, psyllids, leafhoppers and planthoppers are plant-sucking insects of the order Hemiptera that cause dramatic crop losses via direct feeding damage and vectoring of plant pathogens. Chemosensory proteins (CSPs) regulate behavioural and developmental processes in arthropods. Here we show that the CSP Mp10 of the green peach aphid Myzus persicae is an effector that suppresses plant reactive oxygen species (ROS) bursts and the first layer of plant defence responses. Surprisingly, Mp10 homologs are present in diverse plant-feeding hemipteran species, but not blood-feeding ones. An ancestral Mp10-like sequence most likely acquired ROS suppression activity before the divergence of plant-sucking insect species 250 million years ago.

evolutionary biology↗

bioRxiv2017

Linking circadian time to growth rate quantitatively via carbon metabolism

Predicting a multicellular organisms phenotype quantitatively from its genotype is challenging, as genetic effects must propagate across scales. Circadian clocks are intracellular regulators that control temporal gene expression patterns and hence metabolism, physiology and behaviour. Here we explain and predict canonical phenotypes of circadian timing in a multicellular, model organism. We used diverse metabolic and physiological data to combine and extend mathematical models of rhythmic gene expression, photoperiod-dependent flowering, elongation growth and starch metabolism within a Framework Model for the vegetative growth of Arabidopsis thaliana, sharing the model and data files in a structured, public resource. The calibrated model predicted the effect of altered circadian timing upon each particular phenotype in clock-mutant plants under standard laboratory conditions. Altered night-time metabolism of stored starch accounted for most of the decrease in whole-plant biomass, as previously proposed. Mobilisation of a secondary store of malate and fumarate was also mis-regulated, accounting for any remaining biomass defect. We test three candidate mechanisms for the accumulation of these organic acids. Our results link genotype through specific processes to higher-level phenotypes, formalising our understanding of a subtle, pleiotropic syndrome at the whole-organism level, and validating the systems approach to understand complex traits starting from intracellular circuits. This work updates the first biorXiv version, February 2017, https://doi.org/10.1101/105437, with an expanded description and additional analysis of the same core data sets and the same FMv2 model, summary tables and supporting, follow-on data from three further studies with further collaborators. This biorXiv revision constitutes the second version of this report.

systems biology↗