ABSTRACT
The rice blast resistance (R) gene Pi-ta mediates gene-for-gene resistance against strains of the fungus Magnaporthe grisea that express avirulent alleles of AVR-Pita. Using a map-based cloning strategy, we cloned Pi-ta, which is linked to the centromere of chromosome 12. Pi-ta encodes a predicted 928-amino acid cytoplasmic receptor with a centrally localized nucleotide binding site. A single-copy gene, Pi-ta shows low constitutive expression in both resistant and susceptible rice. Susceptible rice varieties contain pi-ta(-) alleles encoding predicted proteins that share a single amino acid difference relative to the Pi-ta resistance protein: serine instead of alanine at position 918. Transient expression in rice cells of a Pi-ta(+) R gene together with AVR-Pita(+) induces a resistance response. No resistance response is induced in transient assays that use a naturally occurring pi-ta(-) allele differing only by the serine at position 918. Rice varieties reported to have the linked Pi-ta(2) gene contain Pi-ta plus at least one other R gene, potentially explaining the broadened resistance spectrum of Pi-ta(2) relative to Pi-ta. Molecular cloning of the AVR-Pita and Pi-ta genes will aid in deployment of R genes for effective genetic control of rice blast disease.
Subject(s)
Alleles , Amino Acid Substitution , Metalloendopeptidases/chemistry , Plant Proteins , Amino Acid Sequence , Base Sequence , Chromosomes, Artificial, Bacterial , Cloning, Molecular , DNA Primers , Metalloendopeptidases/genetics , Molecular Sequence DataABSTRACT
Rice expressing the Pi-ta gene is resistant to strains of the rice blast fungus, Magnaporthe grisea, expressing AVR-Pita in a gene-for-gene relationship. Pi-ta encodes a putative cytoplasmic receptor with a centrally localized nucleotide-binding site and leucine-rich domain (LRD) at the C-terminus. AVR-Pita is predicted to encode a metalloprotease with an N-terminal secretory signal and pro-protein sequences. AVR-Pita(176) lacks the secretory and pro-protein sequences. We report here that transient expression of AVR-Pita(176) inside plant cells results in a Pi-ta-dependent resistance response. AVR-Pita(176) protein is shown to bind specifically to the LRD of the Pi-ta protein, both in the yeast two-hybrid system and in an in vitro binding assay. Single amino acid substitutions in the Pi-ta LRD or in the AVR-Pita(176) protease motif that result in loss of resistance in the plant also disrupt the physical interaction, both in yeast and in vitro. These data suggest that the AVR-Pita(176) protein binds directly to the Pi-ta LRD region inside the plant cell to initiate a Pi-ta-mediated defense response.
Subject(s)
Genes, Fungal , Genes, Plant , Magnaporthe/genetics , Oryza/genetics , Plant Diseases/genetics , Plant Proteins , Binding Sites , Biolistics , Gene Transfer Techniques , Magnaporthe/pathogenicity , Metalloendopeptidases/genetics , Metalloendopeptidases/metabolism , Plant Leaves/microbiology , Protein Binding , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolism , Two-Hybrid System TechniquesABSTRACT
A capillary gas chromatographic-mass spectrometric method using selected ion monitoring was developed for the analysis of cotinine in urine, serum and oral samples. The procedure requires 500 microliters of an oral sample, 250 microliters of a serum sample and 50 microliters of urine and can detect 5 ng/ml cotinine in oral samples, 10 ng/ml in serum and 50 ng/ml in urine with good precision and accuracy. The method was used to determine the cotinine concentration in samples of all three fluids collected from a group of smokers and non-smokers.
Subject(s)
Cotinine/analysis , Saliva/chemistry , Cotinine/blood , Cotinine/urine , Gas Chromatography-Mass Spectrometry , Humans , Indicators and Reagents , Smoking/metabolism , Specimen HandlingABSTRACT
Because peripartal cardiac disease occurs infrequently, its manifestations may be unfamiliar to most physicians. We report two unusual cases of postpartum cardiac disease: one patient presented with cerebral and peripheral arterial embolization, and the second patient developed late eclamptic seizures with subsequent myocardial infarction. Both patients recovered. Nonobstetric physicians should be aware of these pregnancy-associated medical complications to allow prompt diagnosis and aggressive therapy.
Subject(s)
Eclampsia/complications , Heart Diseases/complications , Puerperal Disorders/etiology , Adult , Cardiomyopathy, Dilated/complications , Embolism/etiology , Female , Humans , Intracranial Embolism and Thrombosis/etiology , Myocardial Infarction/etiology , Pregnancy , Thrombosis/complicationsABSTRACT
Due to the evidence that a splenectomized patient is at increased risk for serious infection, nonoperative management of splenic injury, as well as operations designed to preserve functioning splenic tissue, have been recently reported. Most experience in nonoperative management has been in the pediatric and young-adult age groups. We report a case of delayed rupture of the spleen in a middle-aged patient who was successfully managed nonoperatively and was followed with ultrasonography to resolution.
