Biology subjects

Griffiths, S.

Publications and source records attributed to Griffiths, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Extending the seasons at both ends? Understanding the physiological and genetic context required for stay green mediated yield increase in wheat (Triticum aestivum)

Flowering time and monocarpic senescence are tightly environmentally and genetically controlled. Typically, early flowering and staygreen traits are associated with opposing life-history strategies; stress avoidance versus adaptation; with flowering time an overarching regulator of crop cycle length. We developed RIL populations segregating for Ppd-1 and NAM-1 variation, which are otherwise isogenic. Multi-year field experiments enabled exploration and uncoupling of the relationship between heading and staygreen traits. Heading date manipulation enabled introduction of staygreen traits to their target breeding environments, characterised by a hot-finish. Under moderate stress, we report a 2.9% and 1.9% increase in grain width (P<0.0001), and 5.8% and 3.7% increase in TGW (P<0.0001), plus significantly greater yield (P<0.1) for late heading staygreen RILs homozygous for NAM-A1, and NAM-D1 missense variants, respectively. Grain yield increases were proportionate to the delay in senescence, being greater for the NAM-A1 than the NAM-D1 variant. For RIL populations segregating for both traits, senescence variation was observed relative to heading-date. Regarding grain yield, the staygreen trait-associated increase in source size could not compensate for the Ppd-1a associated pleiotropic reduction in sink size, even under hypothesised continental target breeding environments, with trait competition identified. Therefore, to maximise the benefits associated with staygreen traits, especially in early-heading favouring environments required targeted manipulation of source-sink dynamics, and we propose multiple strategies. HighlightStaygreen traits were associated with extending grain fill duration, increasing grain width, TGW and grain yield. There appears an antagonist relationship between earlier heading and staygreen traits.

plant biology↗

bioRxiv2026

Integrating Semi-Dwarf Traits into Diverse Wheat Landraces through CRISPR/Cas9, Base Editing and Prime Editing

The semi dwarf stature of modern wheat varieties is conferred by RHT1 alleles derived from a single Japanese cultivar. These alleles are absent in landrace collections such as the Watkins collection. This constrains the direct use of rich genetic diversity preserved in Watkins landraces. These ancestral accessions, adapted to diverse local environments, harbour valuable traits absent from elite cultivars. Here, we demonstrate a precision breeding approach that integrates CRISPR/Cas9, cytosine base editing, and prime editing to introduce semi-dwarfing alleles into selected Watkins landraces. Our strategy overcomes problems caused by the tall stature of most Watkins accessions, providing rapid and precise modification of the Rht1 locus to confer semi-dwarf phenotypes. High editing efficiencies achieved across multiple Watkins landrace wheat lines confirm the robustness of our approach. By unlocking previously untapped genetic variation and enabling targeted trait integration, this study lays the foundation for modern landrace-based breeding programs, supporting sustainable wheat improvement and global food security.

molecular biology↗

bioRxiv2025

Controlling GRF4-GIF1 Expression for Efficient, Genotype-Independent Transformation Across Wheat Cultivars

Bread wheat (Triticum aestivum L.) plays a vital role in global food security, and its continuous genetic improvement is essential to meet the demands of a rapidly growing world population. Advances in genome sequencing and assembly have positioned wheat as a model crop for functional genomics and have increased the demand for highly efficient, genotype-independent transformation systems. A fusion technology involving a GROWTH-REGULATING FACTOR (GRF) and a GRF-INTERACTING FACTOR (GIF) has emerged as a powerful tool to enhance regeneration efficiency and expand the range of transformable genotypes. In this study, we present an optimized and robust Agrobacterium-mediated wheat transformation protocol incorporating GRF4-GIF1, tested across multiple wheat varieties. Across all tested wheat cultivars, GRF4-GIF1 containing constructs consistently enabled successful transformation, with varied efficiencies depending on the genotype and promotors used to drive the gene fusion. Our method significantly improves transformation efficiency while minimizing GRF4-GIF1 pleiotropic effects, providing a versatile platform for gene function analysis and gene editing. This work represents a critical step toward efficient, genotype-independent transformation in wheat, supporting both research and breeding applications aimed at improving crop resilience, nutritional value, and productivity.

plant biology↗

bioRxiv2025

Unearthing the rhizosphere microbiome recruited by ancestral bread wheat landraces

Crop root traits that modulate the soil microbiome can turn the tide of reduced fertility in intensively farmed land by optimising nutrient availability and resilience to environmental stresses. Advantageous genetic diversity that allows adaptation to nutrient availability is present in historic crop genotypes. The Watkins collection of bread wheat landraces is an unexploited resource, carrying untapped phenotypic traits. Here, we show that the rhizosphere microbiome assembly of these landraces is distinct compared to elite varieties, specifically those that come from ancestral groups (AGs) not used in modern breeding. We used 16S rRNA sequencing to identify changes in microbial communities of rhizosphere soil collected from 81 landraces and two elite varieties. We found high similarity in microbiome recruitment between the elite cultivars and the two AGs genetically closest to the elite. The rhizosphere microbiome of five AGs genetically distant from the elite cultivars showed significant differences in the abundance of taxa involved in nitrogen and carbon turnover, keystone taxa and associations within the microbial network. Our findings suggest that genes to recruit or suppress microbial taxa in the rhizosphere are shared by landraces from these AGs. Selective breeding for traits to control microbial functions can enhance soil productivity and crop performance.

ecology↗

bioRxiv2025

Buying time - increasing yield potential in wheat by extending stem elongation duration

Extending the duration of the stem elongation (SE) phase between terminal spikelet (TS) and anthesis has often been proposed as an avenue to increase wheat yield. However, accurate determination of TS is labour intensive, and existing evidence is often based on a limited number of genotypes observed under controlled conditions. Here, a Buster x Charger population comprising 108 doubled haploid lines was grown across four year-sites under UK field conditions. TS was recorded through meristem dissection and SE duration was measured as the time between TS and ear emergence (EE). Mixed model analysis across year-sites revealed high heritabilities (H2yield = 0.66, H2TS = 0.93, H2SE = 0.89, H2EE = 0.95) and strong genetic correlations between yield and the phenology traits SE and EE (rg = 0.56 and rg = 0.6, respectively). While SE duration was mainly driven by EE, independent QTL for TS suggest that SE could be modified without affecting EE. The positive effect of SE duration on yield was attributed to increased grain number per area as well as increased grain weight, through independent QTL. Although validation in broader genetic backgrounds is needed, these QTL may offer opportunities for further yield increase in a physiological breeding framework. HighlightsO_LILonger stem elongation duration increases grain number. C_LIO_LILonger stem elongation duration increases grain weight. C_LIO_LIIndependent QTL suggest the timing of stem elongation as well as its effect on yield components may be independently selectable. C_LI

genetics↗

bioRxiv2023

Development of a Next Generation SNP Genotyping Array for Wheat

High throughput genotyping arrays have provided a cost effective, reliable and interoperable system for genotyping hexaploid wheat and its related germplasm pool. Existing, highly cited arrays including our 35K Axiom Wheat Breeders genotyping array and the Illumina 90K iSelect array were designed based on a limited amount of varietal sequence diversity and with imperfect knowledge of SNP positions. Recent progress in sequencing wheat varieties and landraces has given us access to a vast pool of SNP diversity, whilst technological improvements in array design has allowed us to fit significantly more probes onto a 384-well format Axiom array than was previously possible. Here we describe a novel High Density Axiom genotyping array, the Triticum aestivum Next Generation array (TaNG), largely derived from whole genome skim sequencing of 204 elite wheat lines and 111 wheat landraces taken from the Watkins "Core Collection". We use a novel "minimal marker" optimisation approach to select up to six SNPs in each 1.5 MB region of the wheat genome with the highest combined varietal discrimination potential. A design iteration step allowed us to test and replace skim-sequence derived SNPs which failed to convert to reliable Axiom markers, resulting in a final design, designated TaNG1.1 with 43,372 SNPs derived from a haplotype-optimised combination of novel SNPs, DArTAG-derived and legacy wheat Axiom markers. We show that this design has an even distribution of SNPs across chromosomes and sub-genomes compared to previous arrays and can be used to generate genetic maps with a significantly higher number of distinct bins than our previous Axiom array. We also demonstrate the improved performance of TaNG1.1 for Genome Wide Association Studies (GWAS) and its utility for Copy Number Variation (CNV) analysis. The array is commercially available, and the marker annotations, initial genotyping results and software used to generate the optimised marker sets are freely available.

genomics↗

bioRxiv2023

Septoria tritici blotch resistance gene Stb15 encodes a lectin receptor-like kinase

Septoria tritici blotch (STB), caused by the Dothideomycete fungus Zymoseptoria tritici, is of one of the most damaging diseases of bread wheat (Triticum aestivum)1 and the target of costly fungicide applications2. In line with the fungus apoplastic lifestyle, STB resistance genes isolated to date encode receptor-like kinases (RLKs) including a wall-associated kinase (Stb6) and a cysteine-rich kinase (Stb16q)3,4. Here, we used genome-wide association studies (GWAS) on a panel of 300 whole-genome shotgun-sequenced diverse wheat landraces (WatSeq consortium) to identify a 99 kb region containing six candidates for the Stb15 resistance gene. Mutagenesis and transgenesis confirmed a gene encoding an intronless G-type lectin RLK (LecRK) as Stb15. The characterisation of Stb15 exemplifies the unexpected diversity of RLKs conferring Z. tritici resistance in wheat.

genetics↗

bioRxiv2023

A high soluble-fibre allele in wheat encodes a defective cell wall peroxidase responsible for dimerization of ferulate moieties on arabinoxylan

Increasing dietary fibre (DF) intake is an important target to improve health and an attractive strategy for this is to increase the fibre content of staple foods, particularly white bread which is the staple food in many countries. DF in wheat white flour is derived principally from the endosperm cell wall polysaccharide arabinoxylan (AX) and the water-extractable form of this (WE-AX) accounts for the majority of soluble dietary fibre (SDF), which is believed to confer particular health benefits. We previously identified QTLs for soluble dietary fibre (SDF) on 1B and 6B chromosomes in wheat in biparental populations. Here we show that the 6B high SDF allele encodes a peroxidase protein (PER1-v) with a single missense compared to the more common low SDF form (PER1). Wheat lines with the natural PER1-v allele and with an induced knock-out mutation in PER1 showed similar characteristics of reduced dimerization of ferulate associated with water-extractable WE-AX. Decreased ferulate dimerization is associated with decreased cross-linking of the WE-AX chains and increased solubility of AX. Transiently expressed PER1_RFP fusion driven by native promoter in wheat endosperm was shown to localise to cell walls whereas PER1-v_RFP did not; we therefore propose that PER1-v lacks capacity to dimerise AX ferulate in vivo due to mis-localisation. PER1 is the first peroxidase reported to be responsible for oxidative coupling of ferulate on AX, a key process in all grass cell walls. Understanding its role and the effect of variants on AX properties offers a route to control the properties of wheat DF in the human diet.

plant biology↗

bioRxiv2022

Development of a high-throughput starch digestibility assay reveals wide variation among the A. E. Watkins wheat landrace collection

Breeding for less digestible starch in wheat can improve the health impact of bread and other wheat foods. Based on an established in vitro starch digestibility assay by Edwards et al. (2019) we developed a high-throughput assay to measure starch digestibility in hydrothermally processed samples for use in forward genetic approaches. Digestibility of purified starch from maize and wheat was measured using both methods and produced comparable results. Using the high-throughput assay, we estimated starch digestibility of 118 wheat landraces from the core Watkins collection and found wide variation across lines and elite UK varieties, (20% to 40% and 31% to 44% starch digested after 90 minutes respectively). Sieved flour fractions and purified starch for selected lines showed altered starch digestibility profiles compared with wholemeal flour, suggesting that matrix properties of flour rather than intrinsic properties of starch granules conferred the low starch digestibility observed.

biochemistry↗

bioRxiv2020

Capturing and Selecting Senescence Variation in Wheat

Senescence is a highly quantitative trait, but in wheat the genetics underpinning senescence regulation remain relatively unknown. To select senescence variation, and ultimately identify novel genetic regulators, accurate characterisation of senescence phenotypes is essential. When investigating senescence, phenotyping efforts often focus on, or are limited to, visual assessment of the flag leaves. However, senescence is a whole plant process, involving remobilisation and translocation of resources into the developing grain. Furthermore, the temporal progression of senescence poses challenges regarding trait quantification and description, whereupon the different models and approaches applied result in varying definitions of apparently similar metrics. To gain a holistic understanding of senescence we phenotyped flag leaf and peduncle senescence progression, alongside grain maturation. Reviewing the literature, we identified techniques commonly applied in quantification of senescence variation and developed simple methods to calculate descriptive and discriminatory metrics. To capture senescence dynamism, we developed the idea of calculating thermal time to different flag leaf senescence scores, for which between year Spearmans rank correlations of r [≥] 0.59, P < 4.7 x 10-5(TT70), identify as an accurate phenotyping method. Following our experience of senescence trait genetic mapping, we recognised the need for singular metrics capable of discriminating senescence variation, identifying Thermal Time to Flag Leaf Senescence score of 70 (TT70) and Mean Peduncle senescence (MeanPed) scores as most informative. Moreover, grain maturity assessments confirmed a previous association between our staygreen traits and grain fill extension, illustrating trait functionality. Here we review different senescence phenotyping approaches and share our experiences of phenotyping two independent RIL populations segregating for staygreen traits. Together, we direct readers towards senescence phenotyping methods we found most effective, encouraging their use when investigating and discriminating senescence variation of differing genetic bases, and to aid trait selection and weighting in breeding and research programs alike.

plant biology↗

bioRxiv2020

Interactions between two QTLs for time to anthesis on spike development and fertility in wheat

Earliness per se (Eps) genes are reported to be important in fine-tuning flowering time in wheat independently of photoperiod (Ppd) and vernalisation (Vrn). Unlike Ppd and Vrn genes, Eps have relatively small effects and their physiological effect along with chromosomal position are not well defined. We evaluated eight lines derived from crossing Paragon and Baj (late and early flowering respectively), vernalisation insensitive, to study the detailed effects of two newly identified QTLs, Eps-7D and Eps-2B and their interactions under field conditions. The effect of both QTLs were minor but their effect was modulated by the allelic status of the other. While the magnitude of effect of these QTLs on anthesis was similar, they are associated with very different profiles of pre-anthesis development which also depends on their interaction. Eps-7D affected both duration before and after terminal spikelet while not affecting final leaf number (FLN) so Eps-7D-early had a faster rate of leaf appearance. Eps-2B acted more specifically in the early reproductive phase and slightly altered FLN without affecting the leaf appearance rate. Both Eps-7D and 2B affected the spike fertility by altering the rate of floret development and mortality. The effect of the latter was very small but consistent in that the -late allele tended to produced more fertile florets.

physiology↗

bioRxiv2020

Delaying or Delivering: Identification of novel NAM-1 alleles which delay senescence to extend grain fill duration of wheat

Senescence is a complex quantitative trait under genetic and environmental control, involving the remobilisation of resources from vegetative tissue into grain. Delayed senescence, or staygreen traits, are associated with conferring stress tolerance, with extended photosynthetic activity hypothesised to sustain grain filling. The genetics of senescence regulation are largely unknown, with senescence variation often correlated with phenological traits. Here, we confirm staygreen phenotypes of two Triticum aestivum cv. Paragon EMS mutants previously identified during a forward genetic screen and selected for their agronomic performance, similar phenology and differential senescence phenotypes. Through grain filling experiments, we confirm a positive relationship between onset of senescence and grain fill duration, reporting an associated [~]14 % increase in final dry grain weight for one mutant, P < 0.05. Recombinant Inbred Line (RIL) populations segregating for senescence were developed for trait mapping purposes, and phenotyped over multiple years under field conditions. Staygreen traits were mapped using exome-capture enabled bulk segregant analysis (BSA), whereupon senescence was quantified, and metrics compared to qualify senescence traits and aid RIL selection. Using BSA we mapped our two staygreen traits to two independent, dominant, loci of 4.8 and 16.7 Mb in size encompassing 56 and 142 genes. Combining single marker association analysis with variant effect prediction, we identified SNPs encoding self-validating mutations located in NAM-1 homoeologues and propose these as gene candidates. SummaryApplying an exome-capture enabled Bulk Segregant Analysis, we identified novel NAM-1 alleles underpinning two staygreen traits associated with enhancing grain fill duration and grain weight

plant biology↗

bioRxiv2020

Wheat developmental traits as affected by the interaction between Eps-7D and temperature under contrasting photoperiods with insensitive Ppd-D1 background

Earliness per se (Eps) genes are important to fine tune adaptation, and studying their probable pleiotropic effect on wheat yield traits is worthwhile. In addition, it has been shown that some Eps genes interact with temperature. We studied two NILs differing in the newly identified Eps-7D but carrying insensitive Ppd-D1 in the background under three temperature regimes (9, 15 and 18 {degrees}C) and two photoperiods (12 h and 24 h). Eps-7D affected time to anthesis as expected and the Eps-7D-late allele extended both the period before and after terminal spikelet. The interaction effect of Eps-7D x temperature was significant but not cross-over: the magnitude and level of significance of the difference between NILs with the late or early allele was affected by the growing temperature (i.e. difference was least at 18 {degrees}C and largest at 9 {degrees}C), and differences in temperature sensitivity was influenced by photoperiod. Rate of leaf initiation was faster in NIL with Eps-7D-early than with the late allele which compensated for the shorter duration of leaf initiation resulting in similar final leaf number between two NILs. Eps-7D-late consistently increased spike fertility through improving floret primordia survival as a consequence of extending the late reproductive phase.

physiology↗

bioRxiv2020

Genotypic differences in wheat yield determinants within a NAM population based on elite parents

Future grain yield (GY) improvements require the identification of beneficial traits within the context of high yield potential and not just based on the pleiotropic effect of traits such as crop height and heading date. We evaluated 1937 lines from Nested Association Mapping (NAM) population derived from 13 bi-parental varietal crosses under field conditions. We selected 493 lines with similar time to anthesis to that of the two checks used in the study (across and within each family) which reduced the range of plant height in the selected lines. Yield components were measured in these 493 lines from which 231 lines were selected by excluding lines with lowest number of grains so excluded low yielding lines. Later the subset of 231 lines were evaluated in two field experiments (2016-17, CS1 and 2017-18, CS2). Numerical and physiological components of grain yield were measured. The two-step selection maximised GY within an acceptable range of variation for height and anthesis. GY in 231 lines showed very high GxE interaction. Taking both seasons together, we selected lines from upper and lower quartile GY groups to identify stable beneficial trait combinations for improved GY. Differences in GY were explained by grain number driven by increased spike dry weight at anthesis (SDWa) and fruiting efficiency (FE). Increased GY was accompanied by sink limitation. The data points towards increases in grain number as the route towards future GY increases in wheat breeding.

physiology↗

bioRxiv2020

Resolving a QTL complex for height, heading, and grain yield on chromosome 3A in bread wheat

Crop height (Ht), heading date (Hd), and grain yield (GY) are interrelated traits in wheat. Independent manipulation of each is important for adaptation and performance. Validated QTL for all three collocate on chromosome 3A in the Avalon x Cadenza population. We asked if these are linked or pleiotropic effects. The region was dissected using recombinants derived from Near Isogenic Lines. It was shown that Ht and Hd are controlled by independent genes. The newly defined Ht QTL interval contained a gene cluster involved in cell wall growth and displaying high levels of differential transcript expression. The Hd locus is much larger and rearranged compared to the reference genome but FT2 is a candidate of particular interest. The Hd effect was shown to act independently of photoperiod and vernalization but did exhibit genotype x environment interaction suggesting a role in ambient temperature sensitivity. It was the Hd locus that was most associated with increased GY of Cadenza alleles, supporting physiological studies proposing that late alleles at this locus increase spike fertility and grain number. The work has uncoupled height from heading and yield and shown that one of very few validated GY QTL in wheat is probably mediated by phenological variation. HighlightThere only are three validated wheat yield QTL. Here, one of them was genetically dissected. This showed that the physiological basis of the yield effect is likely to be phenological.

genetics↗

bioRxiv2019

CONSTRUTION OF A GENETIC MAP OF RILs DERIVED FROM WHEAT (T. AESTIVUM L.) VARIETIES PAMYATII AZIEVA X PARAGON USING HIGH-THROUGHPUT SNP GENOTYPING PLATFORM KASP - COMPETATIVE ALLELE SPECIFIC PCR

The main purposes of the study were i) to develop a first mapping population for bread wheat grown in Kazakhstan, ii) to construct its genetic map for further identification of genes associated with important agronomic traits.\n\nTo the best of our knowledge this is the first segregating population and genetic map developed for Kazakh bread wheat. The work is an example of how plant breeding programs in Kazakhstan have started successfully deploying next generation plant breeding methods.\n\nThe KASP (Compatative Allele Specific PCR) technology of LGC Group and SNP DNA-markers have been exploited to genotype and build a genetic map of the segregating population. The total length of the map was 1376 cM. A total 157 out of initial 178 SNP markers used formed 26 linkage groups leaving 1 duplicated and 20 unassigned markers. The threshold distance between markers was set [≤] 30 cM. Therefore, two linkage groups were obtained for chromosomes such as 2A, 2B, 2D, 3A, 5A, 6B and 7A. Despite one duplicated and 20 unassigned markers, the 157 KASP SNP markers that were mapped spanned A, B and D genomes of wheat. Kosambi Mapping function was employed to calculate recombination units between makers. RILs were developed through SSD method up to F4 generation. Almost 97% of identified alleles were useful in evaluating the populations genetic diversity; the remaining 3% showed no outcome. As a result, 77 DNA markers were mapped for A, 74 for B and 27 for D genomes. The mapping population will be genotyped using high marker density array planform such as Illumina iSelect to obtain a genetic map with a relatively high coverage. Then, the population and high-resolution genetic map will be used to identify genes influencing wheat adaptation in Kazakhstan.

genomics↗

bioRxiv2019

Identification of a major QTL and associated marker for high arabinoxylan fibre in white wheat flour

Dietary fibre (DF) has multiple health benefits, and wheat products are major sources of DF for human health. However, DF is depleted in white flour, which is most widely consumed, compared to wholegrain. The major type of DF in white wheat flour is the cell wall polysaccharide arabinoxylan (AX). Previous studies have identified the Chinese wheat cultivar Yumai 34 as having unusually high contents of AX in both water-soluble and insoluble forms. We have therefore used populations generated from crosses between Yumai 34 and four other wheat cultivars, three with average contents of AX (Ukrainka, Altigo and Claire) and one also having unusually high AX (Valoris), in order to map QTLs for soluble AX (determined as relative viscosity) of aqueous extracts of wholemeal flours) and total AX (determined by enzyme fingerprinting of white flour). A number of QTL were mapped, but most were only detected in one or two crosses. However, all four crosses showed strong QTLs for high RV/total AX on chromosome 1B, with Yumai 34 being the increasing parent, and a KASP marker for the high AX Yumai 34 allele was validated by analysis of high AX lines derived from Yumai 34 but selected by biochemical analysis. A QTL for RV was mapped on chromosome 6B in Yumai 34 x Valoris, with Valoris being the increasing allele, which was consistent with the observation of transgressive segregation for this trait. The data indicate that breeding can be used to develop wheat with high AX fibre in white flour.

genetics↗

bioRxiv2019

Asparagine deprivation causes a reversible inhibition of Human Cytomegalovirus acute virus replication

As obligate intracellular pathogens, viruses rely on the host cell machinery to replicate efficiently, with the host metabolism extensively manipulated for this purpose. High throughput siRNA screens provide a systematic approach for the identification of novel host-virus interactions. Here, we report a large-scale screen for host factors important for human cytomegalovirus (HCMV), consisting of 6,881 siRNAs. We identified 47 proviral factors and 68 antiviral factors involved in a wide range of cellular processes including the mediator complex, proteasome function and mRNA splicing. Focused characterisation of one of the hits, asparagine synthetase (ASNS), demonstrated a strict requirement for asparagine for HCMV replication which leads to an early block in virus replication before the onset of DNA amplification. This effect is specific to HCMV, as knockdown of ASNS had little effect on herpes simplex virus-1 or influenza A virus replication, suggesting the restriction is not simply due to a failure in protein production. Remarkably, virus replication could be completely rescued seven days post-infection with addition of exogenous asparagine, indicating that while virus replication is restricted at an early stage, it maintains the capacity for full replication days after initial infection. This study represents the most comprehensive siRNA screen for the identification of host factors involved in HCMV replication and identifies the non-essential amino acid, asparagine as a critical factor in regulating HCMV virus replication. These results have implications for control of viral latency and the clinical treatment of HCMV in patients.\n\nImportanceHCMV accounts for more than 60% of complications associated with solid organ transplant patients. Prophylactic or preventative treatment with antivirals, such as ganciclovir, reduces the occurrence of early onset HCMV disease. However, late onset disease remains a significant problem and prolonged treatment, especially in patients with suppressed immune systems, greatly increases the risk of antiviral resistance. Very few antivirals have been developed for use against HCMV since the licensing of ganciclovir, and of these, the same viral genes are often targeted, reducing the usefulness of these drugs against resistant strains. An alternative approach is to target host genes essential for virus replication. Here we demonstrate that HCMV replication is highly dependent on levels of the amino acid asparagine and knockdown of a critical enzyme involved in asparagine synthesis results in severe attenuation of virus replication. These results suggest that reducing asparagine levels through dietary restriction or chemotherapeutic treatment could limit HCMV replication in patients.

microbiology↗