Fumonisins comprise a class of carcinogenic mycotoxins produced by Fusarium verticillioides during colonization of maize kernels. In previous work, we identified ZFR1, which is predicted to encode a Zn(II)2Cys6 zinc finger transcription factor required for fumonisin B(1) (FB(1)) production during growth on kernels. In this study, we characterized the role of ZFR1 in colonizing maize kernels and inducing FB(1) biosynthesis. The ZFR1 deletion strain (Deltazfr1) grew approximately 2.5-fold less than the wild-type on endosperm tissue and a variety of other carbon sources, including glucose and amylopectin. However, the Deltazfr1 strain displayed higher alpha-amylase activity and expression of genes involved in starch saccharification than the wild-type, thus indicating that the reduced growth of the Deltazfr1 strain was not due to inhibition of amylolytic enzymes. In the wild-type strain, expression of six genes encoding putative sugar transporters was significantly greater on endosperm tissue than on germ tissue, and expression of at least three of the six genes was negatively affected by disruption of ZFR1. Intriguingly, disruption of FST1 had no effect on growth, kernel colonization or kernel pH but decreased FB(1) production by approximately 82% on maize kernels. Based on these findings, we hypothesize that ZFR1 controls FB(1) biosynthesis by regulating genes involved in the perception or uptake of carbohydrates.
Aims: To differentiate between outer membrane proteins (OMPs) from six Salmonellaenterica serotypes using a Fourier transform infrared (FTIR) spectroscopy method and chemometrics.
Methods and Results: The OMPs from Salmonella serotypes (Typhimurium, Enteritidis, Thomasville, Hadar, Seftenberg and Brandenburg) were isolated using a sarcosyl extraction method. OMP profiles on SDS‐PAGE exhibited two or three bands between 48 and 54 kDa. Spectra of 10 μl of OMP preparations (5 mg ml−1) dried on a gold reflective slide were collected using 128 scans at 4 cm−1 resolution and units of log (1/R) and analyzed using canonical variate analysis (CVA) and linear discriminant analysis (LDA). The CVA of Salmonella OMP spectra in the 1800–1500 cm−1 region separated the serotypes and LDA provided a 100% correct classification.
Conclusions: The use of a FTIR method combined with chemometrics provided better differentiation of Salmonella OMPs than the OMP pattern analysis by SDS‐PAGE.
Significance and Impact of the Study: This is the first study to demonstrate that spectra of OMP extracts from Salmonella serotypes can be used for 100% correct classification of the serotypes studied.
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