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At least 19 recordsLinked to original sources
PubMed1988

Genetic analysis of the fungus, Bremia lactucae, using restriction fragment length polymorphisms.

Restriction fragment length polymorphisms (RFLPs) were developed as genetic markers for Bremia lactucae, the biotrophic Oomycete fungus which causes lettuce downy mildew. By using 55 genomic and cDNA probes, a total of 61 RFLP loci were identified among three heterothallic isolates of B. lactucae. Of these 61 RFLP loci, 53 were heterozygous in at least one of the three strains and thus were informative for linkage analysis in at least one of two F1 crosses that were performed. Analysis of the cosegregation of these 53 RFLPs, eight avirulence loci and the mating type locus allowed the construction of a preliminary genetic linkage map consisting of 13 small linkage groups. Based on the extent of linkage detected among probes, the genome of B. lactucae can be estimated to be approximately 2000 cM. Linkage was detected between a RFLP locus and an avirulence gene, providing a potential starting point for chromosome walking to clone an avirulence gene. The high frequency of DNA polymorphism in naturally occurring isolates and the proper Mendelian segregation of loci detected by low copy number probes indicates that it will be possible to construct a detailed genetic map of B. lactucae using RFLPs as markers. The method of analysis employed here should be applicable to many other outbreeding, heterozygous species for which defined inbred lines are not available.

Blotting, Southern↗
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↗
PubMed1989

Structure and expression of a gene encoding heat-shock protein Hsp70 from the Oomycete fungus Bremia lactucae.

A gene encoding a protein homologous to a 70-kDa heat-shock protein (Hsp70) was isolated from Bremia lactucae and its structure and pattern of expression were determined. This is the first report on the structure of a protein-coding gene from an Oomycete fungus. The cloned gene is a member of a small multigene family. The level of hsp70 mRNA in germlings increases from a low constitutive level in response to heat or cold treatment. A high level of the mRNA is also detected in spores. The hsp70 gene is expressed as a primary transcript of 2241 nucleotides (nt) and contains a continuous open reading frame of 2025 nt. Near the C terminus of the coding sequence is an unusual region that contains repeated enhancer-like sequences. This insert has not been described in other hsp70 genes and is not an intron. Upstream from the 5' terminus of the mRNA are multiple CCAAT motifs, a sequence similar to a consensus heat-shock regulatory element, and an A + T-rich putative 'TATA' box. A canonical polyadenylation recognition sequence is present downstream from the coding sequence. The deduced amino acid sequence is equally similar to yeast and maize Hsp70, providing further evidence of the dissimilarity between Oomycetes and true fungi. The cloning of this gene is part of our strategy to develop a transformation system for B. lactucae.

Amino Acid Sequence↗
PubMedDate not supplied

Highly abundant and stage-specific mRNAs in the obligate pathogen Bremia lactucae.

Germinating spores of the obligate pathogen Bremia lactucae (lettuce downy mildew) contain several unusually abundant species of mRNA. Thirty-nine cDNA clones corresponding to prevalent transcripts were isolated from a library synthesized using poly(A)+ RNA from germinating spores; these clones represented only five distinct classes. Each corresponding mRNA accounted for from 0.4 to 9 percent by mass of poly(A)+ RNA from germinating spores and together represented greater than 20 percent of the mRNA. The expression of the corresponding genes, and a gene encoding Hsp70, was analyzed in spores during germination and during growth in planta. The Hsp70 mRNA and mRNA from one abundant cDNA clone (ham34) were expressed constitutively. Two clones (ham9 and ham12) hybridized only to mRNA from spores and germinating spores. Two clones (ham37 and ham27) showed hybridization specific to germinating spores. Quantification of the number of genes homologous to each cDNA clone indicated that four clones corresponded to one or two copies per haploid genome, and one hybridized to an approximately 11-member family of genes. A sequence of the gene corresponding to ham34 was obtained to investigate its function and to identify sequences conferring high levels of gene expression for use in constructing vectors for the transformation of B. lactucae.

Amino Acid Sequence↗
PubMed1990

Mycoplasma lactucae sp. nov., a sterol-requiring mollicute from a plant surface.

Strain 831-C4T (T = type strain), isolated from the surface of lettuce plants (Lactuca sativa) obtained from a retail food market, was shown to be a sterol-requiring mollicute. Morphological examination of this organism by electron and dark-field microscopic techniques showed that it consists of small, nonhelical, nonmotile, pleomorphic coccoid cells, with individual cells surrounded by a single cytoplasmic membrane. No evidence of a cell wall was observed. The organism grew rapidly in all conventional culture medium formulations for mollicutes in either aerobic or anaerobic environments. The optimum temperature for growth was 30 degrees C, but multiplication occurred at 18 to 37 degrees C. Strain 831-C4T catabolized glucose, but hydrolysis of arginine or urea could not be demonstrated. The genome size of strain 831-C4T was determined to be about 569 megadaltons, while the base composition (guanine-plus-cytosine content) of the DNA was 30.0 mol%. Recent studies in which we compared the 16S rRNA sequences of strain 831-C4T with those of more than 40 other mollicutes indicated that this organism is phylogenetically related to the Spiroplasma-Mycoplasma mycoides clade. Strain 831-C4T was serologically unrelated to the type strains of previously described Mycoplasma species and to 18 other unclassified sterol-requiring isolates cultivated from various animal, plant, or insect sources. Strain 831-C4T (= ATCC 49193) is the type strain of Mycoplasma lactucae sp. nov.

Mycoplasma↗
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↗
PubMed1988

H blood group detection by the L-fucose binding lectin of the green marine alga Ulva lactuca.

Extracts of the green marine alga Ulva lactuca collected along the seashore of Tel-Aviv exhibit hemagglutinating activity towards papain-treated human erythrocytes. This hemagglutinating activity was shown to be inhibited by L-fucose and EDTA, and to be relatively resistant to heating at 60 degrees C, while sensitive to low pH. Like the lectin of Ulex europeus, the Ulva lectin exhibits blood group H specificity. It agglutinates most strongly erythrocytes of blood group 0(H) followed by B greater than A greater than AB. A2 and A2B erythrocytes are agglutinated by it considerably more strongly than A1 and A1B respectively. Bombay 0(hh) type erythrocytes are almost non-reactive. The lectin can be stored at -20 degrees C for years.

ABO Blood-Group System↗
PubMed1988

Isolation, molecular properties and kinetic studies of a strict beta-fucosidase from Lactuca sativa latex. Its possible role in the cell-wall degradation of articulated laticifers.

A beta-fucosidase located in the latex serum of Lactuca sativa has been isolated and purified to homogeneity. This enzyme greatly differs from the other fucosidases already known in that it is strictly specific for the fucosyl residue and for the anomeric beta carbon. It is the first time that such an enzyme is shown to exist. The enzyme is a monomer and its molecular mass is close to 37 kDa. Its sedimentation constant is equal to 2.8 S. It is very stable at pH 5.5 in citrate/phosphate buffer but extensive denaturation occurs up to pH 7.5. Kinetic studies have shown that two ionization steps probably control the rate of the enzymatic hydrolysis. No precise information could be obtained about the possible in vivo role of this beta-fucosidase. However, the pure enzyme can release fucose from the cell walls obtained from hypocotyls of L. sativa. This result may be taken as evidence for the presence of beta-fucosidic links in these walls so that the enzyme could be involved in the differentiation of articulated laticifers.

Amino Acids↗
PubMedDate not supplied

Antifungal action of latex saps from Lactuca sativa L. and Asclepias curassavica L.

Asclepias curassavica and Lactuca sativa latex saps inhibit the growth of Candida albicans because they degrade a great number of yeasts. This was confirmed by scanning and transmission electron microscopy observations. After a contact of 4 h and 6 h yeasts are deformed and emptied of their cytoplasmic content. Moreover, it appears that these saps, particularly Asclepias, also act on the cell wall: the substances presumed to be responsible for these effects were probably terpens and cardenolids but also enzymes, in particular glucanases.

Antifungal Agents↗
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↗
PubMed1976

The influence of borate and calcium on the gel formation of a sulfated polysaccharide from Ulva lactuca.

The water-soluble, sulfated polysaccharide isolated from Ulva lactuca, forms a soft gel when dialysed against sea-water, provided the polysaccharide concentration is 1% or higher and the pH above 7.5. The components of sea-water needed for this gel formation are boric acid and calcium ions. At concentration normally found in sea-water, neither borate nor calcium ions alone produce a gel. It is assumed that the gel formation involves the formation of borate-polysaccharide complexes leading to intermolecular linkages which are stabilized by calcium ions in an unknown manner. This assumption is supported by experiments with extraction of this polysaccharide from the dry seaweed and by the results obtained with the isolated polysaccharide. Agreement between these experiments leads to the conclusion that the sulfated polysaccharide (in vivo) most probably occurs as a gel stabilized by the borate and calcium ions in sea-water.

Borates↗
PubMedDate not supplied

[Effect of outer space factors on lettuce seeds (Lactuca sativa) flown on "Kosmos" biosatellites].

The effect of cosmic radiation on air-dry lettuce (Lactuca sativa) seeds was investigated. It was attempted to discriminate the effects of cosmic ionizing radiation per se and its combination with solar light radiation. It was found that the number of aberrant cells in the seeds exposed to solar light was smaller than that of cells chielded with 0.0008 to 0.0035 g/cm2 foil which could be attributed to photoreactivity.

Cosmic Radiation↗
PubMedDate not supplied

[Effect of single exposure of the seeds of Lactuca sativa to heavy ions of galactic cosmic radiation at orbital manned space stations "Saliut-6" and "Saliut-7"].

This paper presents the results of measuring single heavy ions (HI) of galactic cosmic rays during 40- to 457-day flights of manned orbital stations Salyut-6 and Salyut-7. Cytogenetic analysis of Lactuca sativa seeds showed a significant increase of aberrant cells and cells with multiple chromosome aberrations in seeds hit with HI compared to non-hit++ seeds during flights of 123 to 457 days in duration. There was a good correlation between curves showing aberrant cells as a function of flight of the dose absorbed, viz. 16.0 to 63.4 mGy. These findings suggest a high biological effectiveness of heavy ions of galactic cosmic rays.

Chromosome Aberrations↗
PubMedDate not supplied

[Combined effects of beta radiation and shock wave on the seeds of lettuce Lactuca sativa L].

The effect of shock wave (SW) and beta-radiation (beta) on Lactuca sativa L. seeds was investigated. Exposure to SW at an amplitude of 200 and 600 MPa in various combinations with beta caused a lower survival rate and development of abnormal plants. At an amplitude of 600 MPa, when the SW + beta protocol was used, the maximum amount of abnormalities was seen after 220-240 hours of wetting and when the beta + SW protocol was used the maximum amount of abnormalities was seen after 80-100 hours of wetting. At an amplitude of 600 MPa, the most significant changes in the germination of seeds at different SW and beta combinations were observed. When seeds were first exposed to beta and then to SW, most significant changes were recorded suggesting synergism of the above factors. These observations can be considered as indirect evidence in support of the hypothesis that SW may also occur around the track of a heavy charged particle.

Beta Particles↗
PubMed1975

[Purification and characterization of chloroplast carbonate dehydratase from leaves of Lactuca sativa (author's transl)].

Two isoenzymes of carbonate dehydratase were identified in green leaf tissue of Lactuca sativa. Their molecular weights were found to be 195 000 and 250 000. The lighter isoenzyme (I) was further characterized. It is localized in the chloroplast fraction. With polyacrylamide gel electrophoresis in the presence of dodecyl sulphate, subunits with a molecular weight of 34 000 and higher aggregates of this size could be detected. This is interpreted as an indication of an hexameric enzyme structure. The 900-fold purified polymer contained 5 - 6 atoms of zinc. Amino acid composition and inhibition by acetazolamide (Diamox), cyanide, nitrate, azide and ferricyanide are described.

Acetazolamide↗