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15 recordsLinked to original sources
PubMed1977

Occupational dermatitis from Lactuca sativa (lettuce) and Cichorium (endive). Simultaneous occurrence of immediate and delayed allergy as a cause of contact dermatitis.

Four patients with occupational contact dermatitis to Lactuca sativa had cross-sensitivity to Cichorium endivia. One of the patients also had contact urticaria to Lactuca and Cichorium, and another reacted positively to scratch tests with these plants as a sign of immediate allergy. In two cases such immediate allergy was considered the cause of a vesicular, intense itching eruption within a few minutes of contact with fresh leaves of Lactuca on previously eczematous skin. The severe chronic dermatitis of the hands of these patients is ascribed to combined delayed and immediate allergy.

Adult↗
PubMed2026

Necrotizing fasciitis associated with Acinetobacter lactucae and Bacillus paramobilis infections in 2 dogs.

Two immunocompetent dogs from separate households were presented to a tertiary referral hospital with soft tissue wounds attributable to severe bacterial infection. A 5-y-old, castrated male Golden Retriever dog (case 1) was presented with extensive hemorrhagic cellulitis of the forelimbs and neck that developed over 48-h and was attributable to Acinetobacter lactucae infection. Additionally, an 8-y-old, spayed female Labrador Retriever-mix dog (case 2) sustained a deep penetrating wound over the left hip that progressed over 24 h to necrotizing fasciitis, from which Bacillus paramobilis was isolated. Histopathologic findings in both cases included severe acute, skeletal muscle necrosis and necrosuppurative myofasciitis, dermatitis, and panniculitis with intralesional rod-shaped bacteria. Whole-genome sequencing and phylogenetic analysis of the bacterial isolates revealed numerous cytolytic toxins and other virulence genes carried by the isolates, expanding the profile of these 2 bacteria. To our knowledge, canine cases of A. lactucae and B. paramobilis associated with necrotizing fasciitis have not been reported previously. In both cases, progression from an inciting incident to septic disease was extremely rapid, occurring within 48 h in case 1 and 24 h in case 2, underscoring the fulminant nature of necrotizing fasciitis.

Animals↗
PubMed2025

From aerial drone to quantitative trait locus: leveraging next-generation phenotyping to reveal the genetics of color and height in field-grown Lactuca sativa.

In recent years, accurate and low-cost variant calling has enabled the genotyping of large diversity panels for genome-wide association studies. As a result, phenotyping rather than genotyping is now the rate-limiting step, especially in field experiments. This has created a strong need for high-throughput, accurate, and low-cost in-field phenotyping. Here, we present a genome-wide association study (GWAS) study on 194 field-grown accessions of lettuce (Lactuca sativa). These accessions were non-destructively phenotyped at two time points 15 days apart using a drone equipped with an RGB and multispectral (MSP) camera. Our high-throughput phenotyping approach integrates an RGB- and MSP camera to measure the color and height of lettuce in this large-scale field experiment. We used the mean and other summary statistics, such as median, quantiles, skewness, kurtosis, minimum, and maximum to quantify different aspects of color and height variation in lettuce from the drone images. Using these summary statistics as traits for GWAS, we confirm several previously described genetic associations, now under field conditions, and identify additional novel associations for color and height traits in lettuce.

Lactuca↗
PubMed2025

Diversity of leaf- and root microbiomes among genotypes and market classes of desert-grown lettuce (Lactuca sativa L.).

Plant microbiomes are increasingly acknowledged both as extensions of plant characteristics and as biological factors that influence plant traits important for nutrition and resilience. In the context of global change, manipulation of microbiomes has the potential to complement genetic approaches to enhance crop health and productivity under rising heat and drought stress. Understanding the factors that influence microbial communities and their variation across plant genotypes is essential for developing such capabilities. We employed metabarcoding via the Illumina sequencing platform to investigate microbial communities that occur within healthy leaves and roots of 12 lettuce genotypes (Lactuca sativa L.) grown in a desert agriculture environment. We detected diverse foliar- and root-endophytic fungi and bacteria in field-grown lettuce at the Maricopa Agricultural Center (Arizona, USA). The composition of microbial community structure varied with foliar chemistry and root traits. Notably, levels of zinc and other beneficial nutrients in the leaves were strongly linked with specific endophytes. These results document the lettuce microbiome in desert farming and provide insights into endophytes in lettuce leaves, which are noteworthy because they remain after washing and are regularly ingested.

Lactuca↗
PubMed2026

Plant genetic and root-associated microbial diversity modulate Lactuca sativa responsiveness to a soil inoculum under phosphate deficiency.

Microbial-based approaches offer a promising strategy to decrease the use of chemical fertilizers in agriculture. Among them, arbuscular mycorrhizal fungi (AMF), which extend root surface area and enhance phosphate uptake, and phosphate-solubilizing bacteria (PSB) are particularly relevant. However, their effectiveness depends strongly on plant genetic diversity. To identify genetic markers underlying plant responses to beneficial soil microbes, we studied a panel of 128 fully sequenced Lactuca sativa varieties under controlled phosphate-starvation conditions and treated with AMF and PSB. Lettuce genetic variation showed a strong effect on physiological and morphological responses to microbial inoculation. Genome-wide association studies identified specific genomic regions associated with changes in leaf phosphate content and shoot biomass following treatment. Beyond genetic factors, we observed shifts in fungal β-diversity and increased bacterial α-diversity associated with phenotypic variation. We also identified 44 amplicon sequence variants associated with agriculturally relevant traits. Among these, six bacterial strains were experimentally validated through in vitro and pot experiments for their effects on leaf phosphate concentration and shoot biomass. Overall, we highlighted key genetic, microbial, and physiological mechanisms that may enhance microbial treatments for improved plant phosphate management in lettuce.

16S and ITS metabarcoding↗
PubMed2025

Biosynthetic potential of the culturable foliar fungi associated with field-grown lettuce.

Fungal endophytes and epiphytes associated with plant leaves can play important ecological roles through the production of specialized metabolites encoded by biosynthetic gene clusters (BGCs). However, their functional capacity, especially in crops like lettuce (Lactuca sativa L.), remains poorly understood. We sequenced the genomes of nine fungal isolates, representing Fusarium sp., Fulvia sp., Alternaria alternata, and Alternaria postmessia, from leaves of lettuce grown under field conditions in Arizona, USA. We used antibiotics and secondary metabolite analysis shell (antiSMASH) and the database for automated carbohydrate-active enzyme annotation (dbCAN3), to predict BGCs and carbohydrate-active enzymes (CAZymes) for each strain, and then compared them to conspecific strains from other environments and substrates. Foliar lettuce-associated fungi featured 39-95 BGCs per genome, with substantial overlap between isolates occurring in association with lettuce leaves vs. from other substrates. Species identity was a significant determinant of BGC count, while host type, isolation source, and lifestyle were not. Several BGCs, including those for alternariol and 1,3,6,8-Tetrahydroxynaphthalene (T4HN), showed 100% similarity to characterized minimum information about a biosynthetic gene cluster (MIBiG) clusters based on antiSMASH predictions. Although analysis by biosynthetic gene similarity clustering and prospecting engine (BiG-SCAPE) identified gene cluster families (GCFs) across the dataset, these reference-matching clusters were not always grouped, reflecting methodological differences in how the tools assess similarity. Comparative CAZyme analysis in a focal species (Fulvia sp.) revealed higher gene counts in a foliar lettuce-derived isolate than in tomato (Solanum lycopersicum)-associated strains, challenging assumptions about host chemical complexity. These results highlight the importance of phylogenetic context in shaping fungal functional potential and suggest that selection on microbial traits in edible leafy crops may be more subtle and species-specific than previously assumed. KEY POINTS: • Lettuce-associated fungi feature diverse biosynthetic potential • Phylogeny predicts fungal BGC content more strongly than ecological lifestyle • Findings support genome-informed microbiome strategies for leafy crops.

Lactuca↗
PubMed2026

Heavy metal stress in native plant species: investigating phytoremediation potential through physiological and ISSR/SCoT molecular assessments.

In emerging countries, increased industrial activity has a significant impact on economic growth and urban development. However, the acceleration of industrial processes is accompanied by the release of contaminants such as heavy metals. According to the World Health Organization, one-fourth of all human diseases are caused by environmental contaminants, including heavy metals, which can impair numerous organs such as the neurological system, liver, and reproductive systems. This increased efforts to find effective and sustainable methods to remove heavy metals. Phytoremediation is an environmentally benign method of removing heavy metals using specific plants. Thus, from industrially contaminated locations, common native plant species of Lactuca serriola, Sisymbrium irio, Chenopodium murale, and Cynanchum acutum were selected for this study to assess the mechanisms of their molecular and physiological tolerance. Soil and plants were tested for heavy metals (Cd, Pb, and Cu), and contaminated locations were classified as low and highly polluted. Measurements were made of soluble sugar, protein, secondary metabolites, malondialdehyde, and H2O2. Additionally, inter simple sequence repeat (ISSR), start codon targeted (SCoT), and genomic template stability GTS were used. In heavily polluted areas, all plant species exhibit elevated amounts of sugar, proteins, H2O2, MDA, and secondary metabolites, while total phenolics showed a unique significant interaction (plant-location), where Cynanchum exhibited a hyper-stress phenolic accumulation to cope with toxicity, whereas Chenopodium maintained genomic stability with balanced phenolic level. Based on these findings, both Cynanchum acutum and Chenopodium murale demonstrate superior potential for phytoremediation and warrant further investigation for ecological restoration.

Heavy metal↗
PubMed1975

Breaking of seed dormancy by catalase inhibition.

Germination of some dormant seeds is promoted by solutions of thiourea, sodium nitrite, and hydroxylamine salts. The promotions are accompanied by irreversible inhibition of catalase (EC 1.11.1.6) in extracts from the seeds. The seeds are also promoted in germination by catechol and pyrogallol solutions. These effects are recorded for lettuce (Lactuca sativa L. cv. Grand Rapids) and pigweed (Amaranthus albus L.) seeds. The results indicae that metabolically derived hydrogen peroxide, spared from decomposition by catalase inhibition, oxidizes reduced NADPH required as the oxidant in the pentose pathway of glucose use. The metabolic system for such use of H2O2 involves the enzymes, peroxidase (EC 1.11.1.7) and pyridine nucleotide quinone oxidoreductase (EC 1.6.99.2), which are present in the dormant seed prior to imbibition of water.

Catalase↗
PubMed2025

Differential methylation of a retrotransposon upstream of a MYB gene causes variegation of lettuce leaves, which is abolished by the presence of an (AT)5 repeat in the promoter.

Variegation, a common phenomenon in plants, can be the result of several genetic, developmental, and physiological factors. Leaves of some lettuce cultivars exhibit dramatic red variegation; however, the genetic mechanisms underlying this variegation remain unknown. In this study, we cloned the causal gene for variegation on lettuce leaves and elucidated the underlying molecular mechanisms. Genetic analysis revealed that the polymorphism of variegated versus uniformly red leaves is caused by an "AT" repeat in the promoter of the RLL2A gene encoding a MYB transcription factor. Complementation tests demonstrated that the RLL2A allele (RLL2AV) with (AT)n repeat numbers other than five led to variegated leaves. RLL2AV was expressed in the red spots but not in neighboring green regions. This expression pattern was in concert with a relatively low level of methylation in a retrotransposon inserted in -761 bp of the gene in the red spots compared to high methylation of the retrotransposon in the green region. The presence of (AT)5 in the promoter region, however, stabilized the expression of RLL2A, resulting in uniformly red leaves. In summary, we identified a novel promoter mechanism controlling variegation through inconsistent levels of methylation and showed that the presence of a simple sequence repeat of specific size could stabilize gene expression.

Promoter Regions, Genetic↗
PubMed2026

KCFtools: rapid alignment-free method for introgression screening and GWAS using k-mer profiles.

MOTIVATION: In the era of multiple genome references, researchers often align sequencing reads against distinct assemblies or even multiple references simultaneously. This enables applications such as the detection of introgressed segments or highly variable genomic regions, which are especially prevalent in large-genome crop species such as lettuce or wheat. However, these applications come at the cost of increased computational burden, inconsistencies in mapping methods, and reduced reproducibility across studies. To address these limitations, we developed KCFtools, a Java-based toolkit that identifies the presence and absence of k-mers in nonoverlapping genomic or transcriptomic windows by comparing query and reference genomes. This alignment-free approach enables the efficient computation of an identity score for each window, thereby facilitating robust detection of introgressed or variable regions across genomes. RESULTS: We systematically evaluated the performance and accuracy of the k-mer-based method implemented in KCFtools, benchmarking it against conventional single nucleotide variation-based introgression detection pipelines. Our results demonstrate that KCFtools effectively captures introgressed segments and structurally diverse regions, even in species with fragmented or highly divergent reference genomes. In addition, we extended KCFtools to generate genotype matrices from k-mer variation tables. These matrices are compatible with genome-wide association studies software and allow the identification of loci associated with phenotypic traits. We showcase the utility of this approach by detecting known and novel associations for downy mildew resistance in lettuce, underscoring the pipeline's potential for high-resolution, reference-agnostic population genetic analysis. AVAILABILITY AND IMPLEMENTATION: https://github.com/sivasubramanics/kcftools.

Software↗
PubMed2019

Cold chain and virus-free oral polio booster vaccine made in lettuce chloroplasts confers protection against all three poliovirus serotypes.

To prevent vaccine-associated paralytic poliomyelitis, WHO recommended withdrawal of Oral Polio Vaccine (Serotype-2) and a single dose of Inactivated Poliovirus Vaccine (IPV). IPV however is expensive, requires cold chain, injections and offers limited intestinal mucosal immunity, essential to prevent polio reinfection in countries with open sewer system. To date, there is no virus-free and cold chain-free polio vaccine capable of inducing robust mucosal immunity. We report here a novel low-cost, cold chain/poliovirus-free, booster vaccine using poliovirus capsid protein (VP1, conserved in all serotypes) fused with cholera non-toxic B subunit (CTB) expressed in lettuce chloroplasts. PCR using unique primer sets confirmed site-specific integration of CTB-VP1 transgene cassettes. Absence of the native chloroplast genome in Southern blots confirmed homoplasmy. Codon optimization of the VP1 coding sequence enhanced its expression 9-15-fold in chloroplasts. GM1-ganglioside receptor-binding ELISA confirmed pentamer assembly of CTB-VP1 fusion protein, fulfilling a key requirement for oral antigen delivery through gut epithelium. Transmission Electron Microscope images and hydrodynamic radius analysis confirmed VP1-VLPs of 22.3&#xa0;nm size. Mice primed with IPV and boosted three times with lyophilized plant cells expressing CTB-VP1co, formulated with plant-derived oral adjuvants, enhanced VP1-specific IgG1, VP1-IgA titres and neutralization (80%-100% seropositivity of Sabin-1, 2, 3). In contrast, IPV single dose resulted in <50% VP1-IgG1 and negligible VP1-IgA titres, poor neutralization and seropositivity (<20%, <40% Sabin 1,2). Mice orally boosted with CTB-VP1co, without IPV priming, failed to produce any protective neutralizing antibody. Because global population is receiving IPV single dose, booster vaccine free of poliovirus or cold chain offers a timely low-cost solution to eradicate polio.

Animals↗
PubMed2025

Growth inhibition of Acinetobacter by 5-chloro-indole-3-acetic acid.

The Acinetobacter calcoaceticus-baumannii complex includes high-priority, multidrug-resistant pathogens for which novel antibiotics are urgently needed. Many bacterial strains from this complex harbor a so-called iac gene cluster that codes for the catabolism of indole-3-acetic acid (IAA). Here, we demonstrate that possession and expression of iac genes represent an Achilles' heel for Acinetobacter species, which can be exploited to suppress bacterial growth by treatment with IAA and its analog 5-chloro-IAA.IMPORTANCEAcinetobacter baumannii is a deadly bacterial pathogen and one of the leading causes of hospital-acquired infections worldwide. It is also known for its resistance to many antibiotics currently available. In this study, we show that Acinetobacter bacteria choke on a mixture of IAA and 5-chloro-IAA, offering a path to the discovery and development of a novel drug treatment.

Indoleacetic Acids↗
PubMed2026

Co-occurrence of biofilm formation, acid tolerance, and antibiotic resistance in environmental Escherichia coli associated with lettuce.

BACKGROUND: Environmental niches represent important reservoirs of Escherichia coli with stress-adaptation traits that support persistence outside the host. Contaminated irrigation water and soils can facilitate transfer to fresh produce, where bacterial survival may reduce the effectiveness of downstream control measures. This study investigated the co-occurrence of biofilm formation, acid tolerance, and antibiotic resistance (AR) in environmental E. coli and their contribution to persistence along the farm-to-produce continuum. RESULTS: Eighteen E. coli isolates recovered from irrigation water, soil, and lettuce were characterized using phenotypic assays and genome-based analyses. Most isolates remained susceptible to the majority of tested antibiotics, with multidrug resistance observed in only 11.1% of isolates. In contrast, moderate-to-strong biofilm formation was widespread (83.3%), and several isolates exhibited reduced susceptibility to acetic acid at concentrations relevant to household washing practices. Genotypic screening revealed a broad distribution of adhesion, iron acquisition, biofilm-associated, and plasmid-borne resistance determinants, indicating substantial functional diversity. Significant positive associations were observed between acid tolerance, biofilm formation, and antibiotic resistance, suggesting co-occurrence of stress-adaptation phenotypes rather than definitive evolutionary convergence. While antibiotic resistance phenotypes showed strong concordance with corresponding resistance genes, biofilm formation and acid tolerance were not associated with specific genetic determinants, supporting a multifactorial basis of these traits. CONCLUSIONS: These findings demonstrate that environmental E. coli can combine multiple stress-adaptation mechanisms that enhance persistence across agricultural and food-associated environments, even in the absence of high-risk resistance profiles. The observed co-occurrence of phenotypic traits highlights the potential for co-selection under environmental pressures and underscores the limitations of relying solely on downstream decontamination strategies. Effective risk mitigation requires integrated, preventive approaches targeting pre-harvest contamination and environmental reservoirs.

Biofilms↗