ABSTRACT
The rice gene, Xa21, confers resistance to diverse races of Xanthomonas oryzae pv. oryzae (Xoo) and encodes a receptor-like kinase with leucine-rich repeats in the extra-cellular domain. To identify genes essential for the function of the Xa21 gene, 4,500 IRBB21 ( Xa21 isogenic line in IR24 background) mutants, induced by diepoxybutane and fast neutrons, were screened against Philippine race six (PR6) Xoo for a change from resistance to susceptibility. From two greenhouse screens, 23 mutants were identified that had changed from resistant to fully (6) or partially (17) susceptible to PR6. All fully susceptible mutants carried rearrangements at the Xa21 locus as detected by PCR and Southern hybridization. For the partially susceptible mutants, no changes were detected at the Xa21 locus based on Southern and PCR analyses. However, two of these mutants were confirmed via genetic analysis to have mutations at the Xa21 locus. Partially susceptible mutants exhibited variation in level of susceptibility to different Xoo strains, suggesting that they may carry different mutations required for the Xa21-mediated resistance. The mutants identified in this study provide useful materials for dissecting the Xa21-mediated resistance pathway in rice.
Subject(s)
Immunity, Innate/genetics , Mutation/genetics , Oryza/genetics , Plant Diseases/microbiology , Plant Proteins/genetics , Protein Serine-Threonine Kinases/genetics , Xanthomonas/pathogenicity , Blotting, Southern , Mutagenesis , Oryza/microbiology , Polymerase Chain Reaction , Species SpecificityABSTRACT
Candidate genes involved in both recognition (resistance gene analogs [RGAs]) and general plant defense (putative defense response [DR]) were used as molecular markers to test for association with resistance in rice to blast, bacterial blight (BB), sheath blight, and brown plant-hopper (BPH). The 118 marker loci were either polymerase chain reaction-based RGA markers or restriction fragment length polymorphism (RFLP) markers that included RGAs or putative DR genes from rice, barley, and maize. The markers were placed on an existing RFLP map generated from a mapping population of 116 doubled haploid (DH) lines derived from a cross between an improved indica rice cultivar, IR64, and a traditional japonica cultivar, Azucena. Most of the RGAs and DR genes detected a single locus with variable copy number and mapped on different chromosomes. Clusters of RGAs were observed, most notably on chromosome 11 where many known blast and BB resistance genes and quantitative trait loci (QTL) for blast, BB, sheath blight, and BPH were located. Major resistance genes and QTL for blast and BB resistance located on different chromosomes were associated with several candidate genes. Six putative QTL for BB were located on chromosomes 2, 3, 5, 7, and 8 and nine QTL for BPH resistance were located to chromosomes 3, 4, 6, 11, and 12. The alleles of QTL for BPH resistance were mostly from IR64 and each explained between 11.3 and 20.6% of the phenotypic variance. The alleles for BB resistance were only from the Azucena parent and each explained at least 8.4% of the variation. Several candidate RGA and DR gene markers were associated with QTL from the pathogens and pest. Several RGAs were mapped to BB QTL. Dihydrofolate reductase thymidylate synthase co-localized with two BPH QTL associated with plant response to feeding and also to blast QTL. Blast QTL also were associated with aldose reductase, oxalate oxidase, JAMyb (a jasmonic acid-induced Myb transcription factor), and peroxidase markers. The frame map provides reference points to select candidate genes for cosegregation analysis using other mapping populations, isogenic lines, and mutants.
Subject(s)
Edible Grain/genetics , Plant Diseases/genetics , Aldehyde Reductase/genetics , Alleles , Animals , Bacteria/growth & development , Chromosome Mapping , Crosses, Genetic , Edible Grain/microbiology , Edible Grain/parasitology , Fungi/growth & development , Genetic Markers , Hordeum/genetics , Hordeum/microbiology , Hordeum/parasitology , Immunity, Innate/genetics , Insecta/growth & development , Multigene Family/genetics , Oryza/genetics , Oryza/microbiology , Oryza/parasitology , Oxidoreductases/genetics , Peroxidase/genetics , Plant Diseases/microbiology , Plant Diseases/parasitology , Plant Proteins/genetics , Ploidies , Polymorphism, Restriction Fragment Length , Proto-Oncogene Proteins c-myb/genetics , Quantitative Trait Loci/genetics , Synteny , Zea mays/genetics , Zea mays/microbiology , Zea mays/parasitologyABSTRACT
The Periotest is examined as a possible replacement for outdated, inconsistent dental implant stability diagnosis tools. The Periotest has the advantage of offering reproducible findings by measuring the levels of subclinical mobility using an ultrasonically vibrating probe. The Periotest is successful in assessing the stability status of an implant, but it can detect the quantity of bony osseointegration only in terminal cases. Radiography proved to be a more sensitive method of determining pericervical bone loss; therefore, periapical radiographs in addition to the Periotest device were found to offer the most reliable assessment of an implant's status.
Subject(s)
Alveolar Bone Loss/diagnosis , Dental Implants , Osseointegration , Alveolar Bone Loss/diagnostic imaging , Alveolar Process/diagnostic imaging , Analysis of Variance , Dental Prosthesis Design , Dental Prosthesis Retention , Dental Restoration Failure , Evaluation Studies as Topic , Humans , Linear Models , Percussion/instrumentation , Periodontium/diagnostic imaging , Prospective Studies , Radiography , Reproducibility of Results , Ultrasonography/instrumentationABSTRACT
Endosteal implants fail for a variety of reasons. These include failure to osseointegrate, long-term loss of osseointegration, and invasion of a vital structure or anatomic placement that prohibits its use. This case report describes the removal of an implant because of patient discomfort secondary to invasion of the mandibular canal. These histologic findings offered a unique opportunity to examine an osseointegrated human dental implant section.
Subject(s)
Dental Implantation, Subperiosteal/adverse effects , Dental Implants/adverse effects , Osseointegration , Paresthesia/etiology , Titanium , Dental Restoration Failure , Female , Humans , Lip/innervation , Mandible/diagnostic imaging , Mandible/pathology , Middle Aged , RadiographyABSTRACT
Several transposable elements were isolated from the genome of Xanthomonas oryzae pv. oryzae. These elements and an avirulence gene isolated from X. oryzae pv. oryzae were used as hybridization probes for a collection of X. oryzae pv. oryzae strains from the Philippines. Each of the sequences was present in multiple copies in all strains examined and showed distinct patterns of hybridizing bands. Phenograms were derived from the restriction fragment length polymorphism data obtained for each of the individual probes and for pooled data from multiple probes. The phenograms derived from the different probes differed in topology and, on the basis of bootstrap analysis, were not equally robust. For all of the probes, including the avirulence gene, some groups (even some haplotypes) consisted of multiple races. The strains were grouped into four major clusters on the basis of the two probes giving the highest bootstrap values. These groups were inferred to represent phylogenetic lineages. Three of the six races of X. oryzae pv. oryzae appeared in more than one of the lineages, and another was present in two sublineages. For three of the races, strains representing different phenetic groups were inoculated on rice cultivars carrying 10 resistance genes. Two new races were differentiated, corresponding to pathogen lineages identified by DNA typing. On the basis of DNA and pathotypic analyses, together with information on the spatial and temporal distribution of the pathogen types from this and other studies, a general picture of X. oryzae pv. oryzae evolution in the Philippines is presented.
