RESUMEN
The fungal pathogen, Ophiostomo novo-ulmi, has been responsible for the rapid decline of American elm (Ulmus americana) across North America and remains a serious threat to surviving elm populations. The production of pectinolytic polygalacturonase enzymes has been implicated as a virulence factor for many fungal pathogens, including O. novo-ulmi. Previous work has shown that the targeted disruption of the endopolygalacturonase gene locus epg1 of O. novo-ulmi reduced, but did not eliminate pectinase activity. In the present study, we evaluated the use of RNA interference (RNAi) as a method of suppressing expression of the epg1 locus in O. novo-ulmi and compared its efficiency to the gene disruption method. While there was a reduction in epg1-specific mRNA transcripts and in the amount of polygalacturonase enzyme secreted for both methods of gene regulation, neither method completely suppressed the expression of pectinase activity. There was, however, a significantly greater reduction in both transcript levels and secreted enzyme observed for some of the RNAi transformants. As the first demonstration of RNAi in O. novo-ulmi, this method of gene regulation shows promise in future studies of gene expression and pathogenicity.
Asunto(s)
Regulación hacia Abajo , Proteínas Fúngicas/genética , Ophiostoma/genética , Enfermedades de las Plantas/microbiología , Poligalacturonasa/genética , Interferencia de ARN , Ulmus/microbiología , Proteínas Fúngicas/metabolismo , Regulación Enzimológica de la Expresión Génica , Ophiostoma/enzimología , Poligalacturonasa/metabolismoRESUMEN
BACKGROUND: This study was performed to determine if surgeons' performance of sentinel lymph node biopsy (SLNB) for breast cancer varied with time and to devise a method to continuously evaluate that performance. METHODS: We retrospectively examined the SLNB experience of 13 community surgeons performing 765 SLNBs and 579 concomitant axillary dissections. False-negative rates (FNRs) were assessed for individuals and cohorts defined by caseload. Performance with time was assessed using cumulative sum (CUSUM) analysis. RESULTS: Overall, the SLN identification rate was 94.3%, and FNR was 5.3%. Each surgeon demonstrated variation in identification rate and/or FNR with time. CUSUM analysis provided an effective means to demonstrate when surgeon variation breached performance standards. CONCLUSIONS: Surgeon performance of SLNB varied with time, independent of case load. CUSUM may prove to be a useful statistical tool to evaluate performance before adopting stand-alone SLNB.