Dual sets of chimeric alleles identify specificity sequences for the bE and bW mating and pathogenicity genes of Ustilago maydis.

The b mating-type locus of the fungal plant pathogen Ustilago maydis encodes two multiallelic gene products, bE and bW, that control the formation and maintenance of the infectious cell type. Dimerization via the N-terminal regions of bE and bW proteins encoded by alleles of different specificities establishes a homeodomain-containing transcription factor. The bE and bW products encoded by alleles of like specificities fail to dimerize. We constructed sets of chimeric alleles for the bE1 and bE2 genes and for the bW1 and bW2 genes to identify sequences that control specificity. The mating behavior of strains carrying chimeric alleles identified three classes of specificity: b2 (class I), specificity different from either parental type (class II), and b1 (class III). Crosses between strains carrying bE and bW chimeric alleles identified two short blocks of amino acids that influence specificity and that are located in the N-terminal variable regions of the b proteins. Comparisons of pairs of chimeric alleles encoding polypeptides differing in specificity and differing at single amino acid positions identified 16 codon positions that influence the interaction between bE and bW. Fifteen of these positions lie within the blocks of amino acids identified by crosses between the strains carrying chimeric alleles. Overall, this work provides insight into the organization of the regions that control recognition.

Construction of chimeric alleles with altered specificity at the b incompatibility locus of Ustilago maydis.

Multiallelic incompatibility systems found in many fungi and plants function to limit inbreeding by mediating self versus nonself recognition. The plant pathogenic fungus Ustilago maydis has a locus called b that governs incompatibility. Two multiallelic genes, bE and bW, are present at the b locus. Fusion of haploid strains carrying different alleles at bE and bW establishes an infectious dikaryon capable of pathogenesis on maize (Zea mays). Cells carrying a single type of b locus, whether haploid or dikaryotic, are nonpathogenic. To identify sequences within the bE gene that determine allelic specificity, targeted gene replacement was employed to produce a series of chimeras between the b1E and b2E alleles. Incompatibility tests with strains carrying the chimeric alleles identified a 30- to 48-amino acid region responsible for specificity. Suprisingly, the chimeras with recombination points within this region had a specificity different from both parent alleles. Overall, these results define an important domain in bE involved in self versus nonself recognition.

Clinical and physiological outcomes of a university-hospital pulmonary rehabilitation program.

Pulmonary rehabilitation programs have resulted in improvements in quality of life, capacity for carrying out daily activities, and physical conditioning, as well as reduced hospitalization and cost of care. In our retrospective study, we reviewed the data of 75 patients who had participated in Loma Linda University Medical Center's pulmonary rehabilitation program--in order to determine its effect on survival, progression of disease, and quality of life for a selected group of patients with chronic obstructive pulmonary disease (COPD). A multidisciplinary rehabilitation team evaluated each patient and developed for him a plan of care that included a 2-week inpatient education program. The cumulative survival rate of our group computed by the life table methods was 86.5% at 5 years of rehabilitation, and 64% at 10 years. The mean FEV1 at the beginning of the program was 1.53 1 and the mean FVC was 2.87 1; the mean change in FEV1 was - 45 ml/yr, and in FVC, - 70 ml/yr. By use of a questionnaire, we also found that most of our responding patients felt that their quality of life had improved. Our findings compare favorably with other published data and suggest that it is possible to improve the survival of patients with COPD by early diagnosis, comprehensive treatment, continuing medical care, and home visitation.