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Biomedical subjects

Jane E Parker

Publications and source records attributed to Jane E Parker.

12 recordsLinked to original sources
PubMed2003

Deciphering plant-pathogen communication: fresh perspectives for molecular resistance breeding.

Activation of local and systemic plant defences in response to pathogen attack involves dramatic cellular reprogramming. Over the past 10 years many novel genes, proteins and molecules have been discovered as a result of investigating plant-pathogen interactions. Most attempts to harness this knowledge to engineer improved disease resistance in crops have failed. Although gene efficacy in transgenic plants has often been good, commercial exploitation has not been possible because of the detrimental effects on plant growth, development and crop yield. Biotechnology approaches have now shifted emphasis towards marker-assisted breeding and the construction of vectors containing highly regulated transgenes that confer resistance in several distinct ways.

Bacteria↗
PubMed2003

Plant recognition of microbial patterns.

Animals express an innate immune system against pathogens through receptor-mediated recognition of conserved microbial structures called pathogen-associated molecular patterns (PAMPs). In plants, resistance to invading microorganisms is often governed by specific recognition between plant and pathogen proteins. Perception of more broadly conserved 'general' pathogen elicitors constitutes another layer of plant resistance and prompts questions of where, mechanistically and evolutionarily, this mode of non-self discrimination fits within known systems of microbial surveillance in animals and plants.

Algal Proteins↗
PubMed2003

Massive splenomegaly is associated with significant morbidity after laparoscopic splenectomy.

OBJECTIVE: To evaluate the impact of spleen weight on operative and clinical outcome in a series of 108 consecutive laparoscopic splenectomies. BACKGROUND: Laparoscopic splenectomy as an alternative to open splenectomy for splenomegaly is regarded as controversial. METHODS: Patients underwent laparoscopic splenectomy for a range of hematological disorders between November 1992 and February 2000. Multiple linear and logistic regression analysis were used to assess the effect of massive splenomegaly (>1000 g) on perioperative mortality and morbidity, after adjusting for the joint effects of patient age, weight, pre- and postoperative full blood counts, operating time, estimated blood loss, conversion rate, reoperation rate, and duration of hospital stay. RESULTS: Massive splenomegaly was recorded in 27 of 108 (25%) cases. In this group, splenic weight ranged from 1000 to 4750 g (median, 2500 g). Patients with splenic weight >1000 g had a significantly longer median operating time (170 vs. 102 minutes, P < 0.01), conversion rate (5/27 vs. 4/81, P < 0.05), postoperative morbidity (15/27 vs. 4/81, P < 0.01), and median postoperative stay (5 vs. 3 days, P < 0.01). Multivariate analysis found splenic weight to be the most powerful predictor of morbidity (P < 0.01). Patients with splenomegaly (>1000 g) were 14 times likely to have post operative complications. One patient died 3 days after surgery, following a pulmonary embolus (spleen weight 500 g, mortality 1/108, 0.9%). CONCLUSIONS: Laparoscopic splenectomy is feasible in patients with giant spleens. However, it is associated with greater morbidity, and the advantages of minimal access surgery in this subgroup of patients are not so clear.

Adolescent↗
PubMed2003

Arabidopsis SGT1b is required for SCF(TIR1)-mediated auxin response.

The SCF(TIR1) complex is a central regulator of the auxin response pathway in Arabidopsis. This complex functions as a ubiquitin protein ligase that targets members of the auxin/indoleacetic acid (Aux/IAA) family of transcriptional regulators for ubiquitin-mediated degradation in response to auxin. In an attempt to identify additional factors required for SCF(TIR1) activity, we conducted a genetic screen to isolate enhancers of the auxin response defect conferred by the tir1-1 mutation. Here, we report the identification and characterization of the eta3 mutant. The eta3 mutation interacts synergistically with tir1-1 to strongly enhance all aspects of the tir1 mutant phenotype, including auxin inhibition of root growth, lateral root development, hypocotyl elongation at high temperature, and apical dominance. We isolated the ETA3 gene using a map-based cloning strategy and determined that ETA3 encodes SGT1b. SGT1b was identified recently as a factor involved in plant disease resistance signaling, and SGT1 from barley and tobacco extracts was shown to interact with SCF ubiquitin ligases. We conclude that ETA3/SGT1b is required for the SCF(TIR1)-mediated degradation of Aux/IAA proteins.

Alleles↗
PubMed2002

Regulatory role of SGT1 in early R gene-mediated plant defenses.

Animal SGT1 is a component of Skp1-Cullin-F-box protein (SCF) ubiquitin ligases that target regulatory proteins for degradation. Mutations in one (SGT1b) of two highly homologous Arabidopsis SGT1 genes disable early plant defenses conferred by multiple resistance (R) genes. Loss of SGT1b function in resistance is not compensated for by SGT1a. R genes differ in their requirements for SGT1b and a second resistance signaling gene, RAR1, that was previously implicated as an SGT1 interactor. Moreover, SGT1b and RAR1 contribute additively to RPP5-mediated pathogen recognition. These data imply both operationally distinct and cooperative functions of SGT1 and RAR1 in plant disease resistance.

Amino Acid Motifs↗
PubMed2002

Runaway cell death, but not basal disease resistance, in lsd1 is SA- and NIM1/NPR1-dependent.

LSD1 was defined as a negative regulator of plant cell death and basal disease resistance based on its null mutant phenotypes. We addressed the relationship between lsd1-mediated runaway cell death and signaling components required for systemic acquired resistance (SAR), namely salicylic acid (SA) accumulation and NIM1/NPR1. We present two important findings. First, SA accumulation and NIM1/NPR1 are required for lsd1-mediated runaway cell death following pathogen infection or application of chemicals that mimic SA action. This implies that lsd1-dependent cell death occurs 'downstream' of the accumulation of SA. As SA application triggers runaway cell death in lsd1 but not wild-type plants, we infer that LSD1 negatively regulates an SA-dependent signal leading to cell death. Thus SA is both a trigger and a required mediator of lsd1 runaway cell death. Second, neither SA accumulation nor NIM1/NPR1 function is required for the basal resistance operating in lsd1. Therefore LSD1 negatively regulates a basal defense pathway that can act upstream or independently of both NIM1/NPR1 function and SA accumulation following avirulent or virulent pathogen challenge. Our data, together with results from other studies, point to the existence of an SA-dependent 'signal potentiation loop' controlling HR. Continued escalation of signaling in the absence of LSD1 leads to runaway cell death. We propose that LSD1 is a key negative regulator of this signal potentiation.

Apoptosis↗
PubMed2002

Arabidopsis RPP4 is a member of the RPP5 multigene family of TIR-NB-LRR genes and confers downy mildew resistance through multiple signalling components.

In Arabidopsis, RPP4 confers resistance to Peronospora parasitica (P.p.) races Emoy2 and Emwa1 (downy mildew). We identified RPP4 in Col-0 as a member of the clustered RPP5 multigene family encoding nucleotide-binding leucine-rich repeat proteins with Toll/interleukin-1 receptor domains. RPP4 is the orthologue of RPP5 which, in addition to recognizing P.p. race Noco2, also mediates resistance to Emoy2 and Emwa1. Most differences between RPP4 and RPP5 occur in residues that constitute the TIR domain and in LRR residues that are predicted to confer recognition specificity. RPP4 requires the action of at least 12 defence components, including DTH9, EDS1, PAD4, PAL, PBS2, PBS3, SID1, SID2 and salicylic acid. The ndr1, npr1 and rps5-1 mutations partially compromise RPP4 function in cotyledons but not in true leaves. The identification of RPP4 as a TIR-NB-LRR protein, coupled with its dependence on certain signalling components in true leaves, is consistent with the hypothesis that distinct NB-LRR protein classes differentially signal through EDS1 and NDR1. Our results suggest that RPP4-mediated resistance is developmentally regulated and that in cotyledons there is cross-talk between EDS1 and NDR1 signalling and processes regulating systemic acquired resistance.

Amino Acid Sequence↗
PubMed2002

Allogeneic stem cell transplantation in the myelodysplastic syndromes: interim results of outcome following reduced-intensity conditioning compared with standard preparative regimens.

Conventional allogeneic stem cell transplantation (SCT) for myelodysplastic syndrome (MDS) is associated with excessive procedure-related mortality. The outcome following volunteer-unrelated donor (VUD) or sibling allogeneic SCT was therefore evaluated in 23 MDS patients conditioned with reduced-intensity regimens (fludarabine/busulphan/Campath-1H) because of advanced age (48 vs 37 years, P = 0.002) and/or co-morbidity (19 vs 3, P < 0.0001) which precluded conventional transplantation, and compared with 29 treated with standard protocols [busulphan/cyclophosphamide (Bu/Cy); Bu/Cy/total-body irradiation/Campath-1G]. Graft-versus-host disease (GVHD) prophylaxis comprised of cyclosporine/methotrexate. One hundred per cent donor engraftment (variable number tandem repeat analysis/cytogenetics/fluorescence in situ hybridization) was achieved in 18/19 (95%) evaluable patients receiving reduced-intensity regimens, although six (32%) have subsequently shown mixed chimaerism. Reduced-intensity conditioning was associated with significantly reduced duration of aplasia, less mucositis, fever, antibiotic, analgesia, parenteral nutrition use, less acute and chronic GVHD, and lower early procedure-related mortality [two (9%) vs nine (31%), P < 0.05]. Six patients relapsed (two standard, four reduced-intensity) and two (reduced-intensity) experienced late graft failure. The 2 year actuarial overall/disease-free survival (OS/DFS) was 48/39% in the reduced-intensity arm and 44/44% in the standard group. The 2 year non-relapse mortality was 31% and 50% respectively. In VUD recipients, OS was superior in the reduced-intensity arm (49%vs 34%). Predictors of DFS included good/intermediate-risk karyotype, low/intermediate-1 International Prognostic Scoring system score, human leucocyte antigen compatibility and attainment of complete remission. Our data demonstrates that VUD or sibling allogeneic SCT following reduced-intensity conditioning is feasible in high-risk MDS patients considered unsuitable for standard transplantation and is associated with comparable 3.5 year DFS to those receiving conventional regimens.

Adult↗
PubMed2002

An EDS1 orthologue is required for N-mediated resistance against tobacco mosaic virus.

In Arabidopsis, EDS1 is essential for disease resistance conferred by a structural subset of resistance (R) proteins containing a nucleotide-binding site, leucine-rich-repeats and amino-terminal similarity to animal Toll and Interleukin-1 (so-called TIR-NBS-LRR proteins). EDS1 is not required by NBS-LRR proteins that possess an amino-terminal coiled-coil motif (CC-NBS-LRR proteins). Using virus-induced gene silencing (VIGS) of a Nicotiana benthaminana EDS1 orthologue, we investigated the role of EDS1 in resistance specified by structurally distinct R genes in transgenic N. benthamiana. Resistance against tobacco mosaic virus mediated by tobacco N, a TIR-NBS-LRR protein, was EDS1-dependent. Two other R proteins, Pto (a protein kinase), and Rx (a CC-NBS-LRR protein) recognizing, respectively, a bacterial and viral pathogen did not require EDS1. These data, together with the finding that expression of N. benthamiana and Arabidopsis EDS1 mRNAs are similarly regulated, lead us to conclude that recruitment of EDS1 by TIR-NBS-LRR proteins is evolutionarily conserved between dicotyledenous plant species in resistance against bacterial, oomycete and viral pathogens. We further demonstrate that VIGS is a useful approach to dissect resistance signaling pathways in a genetically intractable plant species.

Amino Acid Sequence↗
PubMed2002

Arabidopsis RAR1 exerts rate-limiting control of R gene-mediated defenses against multiple pathogens.

We have identified the Arabidopsis ortholog of barley RAR1 as a component of resistance specified by multiple nucleotide binding/Leu-rich repeat resistance (R) genes recognizing different bacterial and oomycete pathogen isolates. Characterization of partially and fully defective rar1 mutations revealed that wild-type RAR1 acts as a rate-limiting regulator of early R gene-triggered defenses, determining the extent of pathogen containment, hypersensitive plant cell death, and an oxidative burst at primary infection sites. We conclude that RAR1 defense signaling function is conserved between plant species that are separated evolutionarily by 150 million years. RAR1 encodes a protein with two zinc binding (CHORD) domains that are highly conserved across eukaryotic phyla, and the single nematode CHORD-containing homolog, Chp, was found previously to be essential for embryo viability. An absence of obvious developmental defects in null Arabidopsis rar1 mutants favors the notion that, in contrast, RAR1 does not play a fundamental role in plant development.

Amino Acid Sequence↗
PubMed2001

The role of apoptosis in the pathogenesis of the myelodysplastic syndromes.

The paradoxical occurrence of peripheral cytopenias despite a normo/hypercellular marrow in myelodysplastic syndromes (MDS) has been attributed to excessive intramedullary hematopoietic cell apoptosis. It has also been postulated that abrogation of programmed cell death (PCD) may underlie MDS transformation to acute myeloid leukemia (AML). Despite overwhelming evidence for a role of aberrant apoptosis in myelodysplasia, the molecular mechanisms responsible for such changes have not been elucidated. This paper summarizes current evidence implicating a role for altered PCD in MDS and outlines potential cellular mechanisms whereby hematopoietic progenitor cell apoptosis may be dysregulated.

Apoptosis↗