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S Somerville

Publications and source records attributed to S Somerville.

17 recordsLinked to original sources
PubMed2001

Cell-autonomous expression of barley Mla1 confers race-specific resistance to the powdery mildew fungus via a Rar1-independent signaling pathway.

The barley Mla locus encodes 28 characterized resistance specificities to the biotrophic fungal pathogen barley powdery mildew. We describe a single-cell transient expression assay using entire cosmid DNAs to pinpoint Mla1 within the complex 240-kb Mla locus. The MLA1 cDNA encodes a 108-kD protein containing an N-terminal coiled-coil structure, a central nucleotide binding domain, and a C-terminal leucine-rich repeat region; it also contains a second short open reading frame at the 5' end that has a possible regulatory function. Although most Mla-encoded resistance specificities require Rar1 for their function, we used the single-cell expression system to demonstrate that Mla1 triggers full resistance in the presence of the severely defective rar1-2 mutant allele. Wheat contains an ortholog of barley Mla, designated TaMla, that is tightly linked to (0.7 centimorgan) but distinct from a tested resistance specificity at the complex Pm3 locus to wheat powdery mildew. Thus, the most polymorphic powdery mildew resistance loci in barley and wheat may have evolved in parallel at two closely linked homeoloci. Barley Mla1 expressed in wheat using the single-cell transformation system failed to trigger a response to any of the wheat powdery mildew Avr genes tested, indicating that AvrMla1 is not genetically fixed in wheat mildew strains.

Alleles↗
PubMed2000

Isolation and characterization of powdery mildew-resistant Arabidopsis mutants.

A compatible interaction between a plant and a pathogen is the result of a complex interplay between many factors of both plant and pathogen origin. Our objective was to identify host factors involved in this interaction. These factors may include susceptibility factors required for pathogen growth, factors manipulated by the pathogen to inactivate or avoid host defenses, or negative regulators of defense responses. To this end, we identified 20 recessive Arabidopsis mutants that do not support normal growth of the powdery mildew pathogen, Erysiphe cichoracearum. Complementation analyses indicated that four loci, designated powdery mildew resistant 1-4 (pmr1-4), are defined by this collection. These mutants do not constitutively accumulate elevated levels of PR1 or PDF1.2 mRNA, indicating that resistance is not simply due to constitutive activation of the salicylic acid- or ethylene- and jasmonic acid-dependent defense pathways. Further Northern blot analyses revealed that some mutants accumulate higher levels of PR1 mRNA than wild type in response to infection by powdery mildew. To test the specificity of the resistance, the pmr mutants were challenged with other pathogens including Pseudomonas syringae, Peronospora parasitica, and Erysiphe orontii. Surprisingly, one mutant, pmr1, was susceptible to E. orontii, a very closely related powdery mildew, suggesting that a very specific resistance mechanism is operating in this case. Another mutant, pmr4, was resistant to P. parasitica, indicating that this resistance is more generalized. Thus, we have identified a novel collection of mutants affecting genes required for a compatible interaction between a plant and a biotrophic pathogen.

Animals↗
PubMed2000

Chasing the dream: plant EST microarrays.

DNA microarray technology is poised to make an important contribution to the field of plant biology. Stimulated by recent funding programs, expressed sequence tag sequencing and microarray production either has begun or is being contemplated for most economically important plant species. Although the DNA microarray technology is still being refined, the basic methods are well established. The real challenges lie in data analysis and data management. To fully realize the value of this technology, centralized databases that are capable of storing microarray expression data and managing information from a variety of sources will be needed. These information resources are under development and will help usher in a new era in plant functional genomics.

Chromosome Mapping↗
PubMed2000

GSM cell phones can interfere with ionizing radiation dose monitoring equipment.

Cell phone use is growing worldwide. These phones transmit to adjacent base stations using radiofrequency signals in the microwave range (approximately 900-approximately 1800 MHz). Portable electronic dose monitoring equipment is used in hospitals and other institutions to monitor and control levels of exposure to ionizing radiation, and to reassure staff. The objective of this paper is to investigate the effect of mobile phones on a sample of dose monitoring devices. Two mobile phones (Siemens C25 and Motorola CD930) were used in the study. Field strengths were measured to be in the range 0 V m-1 to over 100 V m-1, depending on the distance from the phone, and were strongest at the beginning of a call. Personal electronic dosemeters (n = 7), portable dose monitors (n = 4) and contamination monitors (n = 2) were assessed. All the units were in service. Three of the personal dosemeters showed abnormal responses when exposed to mobile phone transmission. One dosemeter (Siemens EPD-2) registered doses equivalent to a dose rate of 99 mSv h-1. In addition, two of the portable dosemeters and one of the contamination monitors also gave an abnormal response. Interference was observed across a number of detector types from a number of manufacturers. Modern cell phones can interfere with ionizing radiation dose monitoring equipment. This should be taken into account when distributing these devices and when assessing results generated by them. Electromagnetic compatibility testing should form part of the commissioning and specification protocol for new dose monitoring equipment.

Electromagnetic Fields↗
PubMed2000

Atrial fibrillation: a comparison of methods to identify cases in general practice.

The importance of atrial fibrillation as a treatable risk factor for stroke is well established. Less is known about how to find previously unidentified cases within the community so that antithrombotic treatment can be offered to a wider group of at-risk patients. The aim of our study was to examine ways to improve the efficiency of practice-based screening for atrial fibrillation, including issues of time and financial cost. We used different combinations of pulse palpation and interpretation of 12-lead and bipolar electrocardiographs as carried out by practice nurses. The best strategy for the detection of atrial fibrillation in a practice population would appear to be to screen all eligible subjects by nurse pulse palpation, followed by 12-lead electrocardiograph readings in those who have a pulse suggestive of atrial fibrillation. The electrocardiograph interpretation can be undertaken effectively by a trained nurse.

Aged↗
PubMed1999

Plant functional genomics.

Nucleotide sequencing of the Arabidopsis genome is nearing completion, sequencing of the rice genome has begun, and large amounts of expressed sequence tag information are being obtained for many other plants. There are many opportunities to use this wealth of sequence information to accelerate progress toward a comprehensive understanding of the genetic mechanisms that control plant growth and development and responses to the environment.

Arabidopsis↗
PubMed1999

Comparison of Erysiphe cichoracearum and E. cruciferarum and a survey of 360 Arabidopsis thaliana accessions for resistance to these two powdery mildew pathogens.

In previous work, UEA1 and UCSC1, two geographically distinct, powdery mildew isolates, were recognized for their ability to infect Arabidopsis thaliana. We have clarified the identity of these isolates by determining their host ranges, reexamining their morphology, and comparing their DNA sequences for the 5.8S ribosomal RNA and two flanking internal transcribed spacer sequences. These experiments confirm that UEA1 is a member of Erysiphe cruciferarum and that UCSC1 belongs to E. cichoracearum. Interactions of the two Erysiphe isolates with 360 A. thaliana accessions were examined to provide a comprehensive profile of naturally occurring powdery mildew resistance in this weedy species. The majority of A. thaliana accessions (213) were susceptible to both isolates. Among the accessions exhibiting some degree of resistance, most (84) responded differentially to UEA1 and UCSC1 and the remainder were resistant to both isolates. Notably, resistance to UCSC1 cosegregated with RPW7, a locus previously demonstrated to confer resistance to UEA1 in Ms-0 x Landsberg (erecta) crosses. With this large collection of resistant accessions, questions about species specificity, genetic diversity and the evolution of resistance to powdery mildews can be addressed.

Arabidopsis↗
PubMed1999

Tilling the soil: nurturing the seeds of patient and family education.

Effective patient and family education has become most essential in today's changing health care environment. The importance of patient education is reflected in the organizational performance standards of the Joint Commission on Accreditation of Healthcare Organizations. To keep abreast of these rapid changes, we decided to evaluate and enhance our existing cardiac education program. This article presents our analysis that effective patient and family education must be a coordinated effort across the cardiac continuum. New teaching tools were established to assist in increasing the patients' knowledge base, and consequently empower patients to make better decisions regarding their care.

Adult↗
PubMed1997

Signalling pathways: a common theme in plants and animals?

The unexpected notion that disease resistance mechanisms may use similar regulatory pathways to developmental processes has emerged from recent advances in understanding signal transduction pathways in insects, mammals and plants.

Animal Population Groups↗
PubMed1996

Isolation and characterization of two novel genes expressed in germinating conidia of the obligate biotroph Erysiphe graminis f.sp. hordei.

A cDNA library was constructed from germinating conidia of the obligate biotrophic fungus, Erysiphe graminis DC ex Mérat f.sp. hordei Em. Marchal (Egh). Subtractive hybridization and differential screening were carried out. Two cDNA clones, cEgh7 and cEgh16, which were highly expressed in germinating conidia, but not in ungerminated conidia, were selected for further characterization. The corresponding genomic sequences, gEgh7 and gEgh16, were isolated from a cosmid library and sequenced. The gEgh7 gene contains an open reading frame (ORF) that codes for a 249-amino-acid (aa), Pro-rich polypeptide with a repeated primary structure. Expression studies in planta indicated that gEgh7 may have a function in the development and maturation of conidia. The ORF of gEgh16 is interrupted by two introns of 91 and 119 bp. It encodes a 251-aa polypeptide of unknown function. This gene belongs to a multigene family and is expressed during all developmental stages of Egh in planta and may be associated with hyphal growth.

Amino Acid Sequence↗
PubMed1996

Cloning and characterization of a highly repeated DNA sequence in Hordeum vulgare L.

A novel repetitive DNA sequence, R10hvcop, has been identified in the barley (Hordeum vulgare L.) genome. This 830 base pair (bp) DNA sequence has a 606-bp open reading frame and is present as approximately 1.96 x 10(5) copies per haploid barley genome. Southern blot analysis revealed that repetitive DNA elements containing R10hvcop and related sequences were dispersed within the barley chromosomes. Sequences similar to R10hvcop were also found in wheat (Triticum aestivum L.), rye (Secale cereale L.), and oat (Avena sativa L.) with copy numbers of 8 x 10(4), 1.39 x 10(5), and 7.9 x 10(4) per haploid genome, respectively. Sequences similar to R10hvcop were also present in the corn (Zea mays L. ssp. mays) genome, but they were not highly repeated. Barley, wheat, rye, oat, and corn showed species-specific restriction fragment length polymorphisms of R10hvcop and related sequences. Computer-based similarity searches revealed that R10hvcop is closely related to reverse transcriptase genes in retrotransposon-like elements of several plant species and of Drosophila. The highly repetitive nature, interspersed distribution, and high degree of similarity to reverse transcriptase genes suggests that R10hvcop contains the sequence of a diverged reverse transcriptase gene.

Base Sequence↗
PubMed1994

Genes galore: a summary of methods for accessing results from large-scale partial sequencing of anonymous Arabidopsis cDNA clones.

High-throughput automated partial sequencing of anonymous cDNA clones provides a method to survey the repertoire of expressed genes from an organism. Comparison of the coding capacity of these expressed sequence tags (ESTs) with the sequences in the public data bases results in assignment of putative function to a significant proportion of the ESTs. Thus, the more than 13,400 plant ESTs that are currently available provide a new resource that will facilitate progress in many areas of plant biology. These opportunities are illustrated by a description of the results obtained from analysis of 1500 Arabidopsis ESTs from a cDNA library prepared from equal portions of poly(A+) mRNA from etiolated seedlings, roots, leaves, and flowering inflorescences. More than 900 different sequences were represented, 32% of which showed significant nucleotide or deduced amino acid sequences similarity to previously characterized genes or proteins from a wide range of organisms. At least 165 of the clones had significant deduced amino acid sequence homology to proteins or gene products that have not been previously characterized from higher plants. A summary of methods for accessing the information and materials generated by the Arabidopsis cDNA sequencing project is provided.

Amino Acid Sequence↗