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Magnaporthe oryzae is a fungal plant pathogen of many grasses including rice. Since arabinoxylan is one of the major components of the plant cell wall of grasses, M. oryzae is likely to degrade this polysaccharide for supporting its growth in infected leaves. D-Xylose is released from arabinoxylan by fungal depolymerising enzymes and catabolized through the pentose pathway. The expression of genes involved in these pathways is under control of the transcriptional activator XlnR/Xlr1, conserved among filamentous ascomycetes. In this study, we identified M. oryzae genes involved in the pentose catabolic pathway (PCP) and their function during infection, including the XlnR homolog, XLR1, through the phenotypic analysis of targeted null mutants. Growth of the Delta xlr1 strain was reduced on D-xylose and xylan, but unaffected on L-arabinose and arabinan. A strong reduction of PCP gene expression was observed in the Delta xlr1 strain on D-xylose and L-arabinose. However, there was no significant difference in xylanolytic and cellulolytic enzyme activities between the Delta xlr1 mutant and the reference strain. These data demonstrate that XLR1 encodes the transcriptional activator of the PCP in M. oryzae, but does not appear to play a role in the regulation of the (hemi-) cellulolytic system in this fungus. This indicates only partial similarity in function between Xlr1 and A. niger XlnR. The deletion mutant of D-xylulose kinase encoding gene (XKI1) is clearly unable to grow on either D-xylose or L-arabinose and showed reduced growth on xylitol, L-arabitol and xylan. Delta xki1 displayed an interesting molecular phenotype as it over-expressed other PCP genes as well as genes encoding (hemi-) cellulolytic enzymes. However, neither Delta xlr1 nor Delta xki1 showed significant differences in their pathogeny on rice and barley compared to the wild type, suggesting that p-xylose catabolism is not required for fungal growth in infected leaves. (C) 2013 Elsevier Inc. All rights, Magnaporthe oryzae is a fungal plant pathogen of many grasses including rice. Since arabinoxylan is one of the major components of the plant cell wall of grasses, M. oryzae is likely to degrade this polysaccharide for supporting its growth in infected leaves. D-Xylose is released from arabinoxylan by fungal depolymerising enzymes and catabolized through the pentose pathway. The expression of genes involved in these pathways is under control of the transcriptional activator XlnR/Xlr1, conserved among filamentous ascomycetes. In this study, we identified M. oryzae genes involved in the pentose catabolic pathway (PCP) and their function during infection, including the XlnR homolog, XLR1, through the phenotypic analysis of targeted null mutants. Growth of the Delta xlr1 strain was reduced on D-xylose and xylan, but unaffected on L-arabinose and arabinan. A strong reduction of PCP gene expression was observed in the Delta xlr1 strain on D-xylose and L-arabinose. However, there was no significant difference in xylanolytic and cellulolytic enzyme activities between the Delta xlr1 mutant and the reference strain. These data demonstrate that XLR1 encodes the transcriptional activator of the PCP in M. oryzae, but does not appear to play a role in the regulation of the (hemi-) cellulolytic system in this fungus. This indicates only partial similarity in function between Xlr1 and A. niger XlnR. The deletion mutant of D-xylulose kinase encoding gene (XKI1) is clearly unable to grow on either D-xylose or L-arabinose and showed reduced growth on xylitol, L-arabitol and xylan. Delta xki1 displayed an interesting molecular phenotype as it over-expressed other PCP genes as well as genes encoding (hemi-) cellulolytic enzymes. However, neither Delta xlr1 nor Delta xki1 showed significant differences in their pathogeny on rice and barley compared to the wild type, suggesting that p-xylose catabolism is not required for fungal growth in infected leaves. (C) 2013 Elsevier Inc. All rights

Magnaporthe oryzae is a fungal plant pathogen of many grasses including rice. Since arabinoxylan is one of the major components of the plant cell wall of grasses, M. oryzae is likely to degrade this polysaccharide for supporting its growth in infected leaves. D-Xylose is released from arabinoxylan by fungal depolymerising enzymes and catabolized through the pentose pathway. The expression of genes involved in these pathways is under control of the transcriptional activator XlnR/Xlr1, conserved among filamentous ascomycetes. In this study, we identified M. oryzae genes involved in the pentose catabolic pathway (PCP) and their function during infection, including the XlnR homolog, XLR1, through the phenotypic analysis of targeted null mutants. Growth of the Delta xlr1 strain was reduced on D-xylose and xylan, but unaffected on L-arabinose and arabinan. A strong reduction of PCP gene expression was observed in the Delta xlr1 strain on D-xylose and L-arabinose. However, there was no significant difference in xylanolytic and cellulolytic enzyme activities between the Delta xlr1 mutant and the reference strain. These data demonstrate that XLR1 encodes the transcriptional activator of the PCP in M. oryzae, but does not appear to play a role in the regulation of the (hemi-) cellulolytic system in this fungus. This indicates only partial similarity in function between Xlr1 and A. niger XlnR. The deletion mutant of D-xylulose kinase encoding gene (XKI1) is clearly unable to grow on either D-xylose or L-arabinose and showed reduced growth on xylitol, L-arabitol and xylan. Delta xki1 displayed an interesting molecular phenotype as it over-expressed other PCP genes as well as genes encoding (hemi-) cellulolytic enzymes. However, neither Delta xlr1 nor Delta xki1 showed significant differences in their pathogeny on rice and barley compared to the wild type, suggesting that p-xylose catabolism is not required for fungal growth in infected leaves. (C) 2013 Elsevier Inc. All rights, Magnaporthe oryzae is a fungal plant pathogen of many grasses including rice. Since arabinoxylan is one of the major components of the plant cell wall of grasses, M. oryzae is likely to degrade this polysaccharide for supporting its growth in infected leaves. D-Xylose is released from arabinoxylan by fungal depolymerising enzymes and catabolized through the pentose pathway. The expression of genes involved in these pathways is under control of the transcriptional activator XlnR/Xlr1, conserved among filamentous ascomycetes. In this study, we identified M. oryzae genes involved in the pentose catabolic pathway (PCP) and their function during infection, including the XlnR homolog, XLR1, through the phenotypic analysis of targeted null mutants. Growth of the Delta xlr1 strain was reduced on D-xylose and xylan, but unaffected on L-arabinose and arabinan. A strong reduction of PCP gene expression was observed in the Delta xlr1 strain on D-xylose and L-arabinose. However, there was no significant difference in xylanolytic and cellulolytic enzyme activities between the Delta xlr1 mutant and the reference strain. These data demonstrate that XLR1 encodes the transcriptional activator of the PCP in M. oryzae, but does not appear to play a role in the regulation of the (hemi-) cellulolytic system in this fungus. This indicates only partial similarity in function between Xlr1 and A. niger XlnR. The deletion mutant of D-xylulose kinase encoding gene (XKI1) is clearly unable to grow on either D-xylose or L-arabinose and showed reduced growth on xylitol, L-arabitol and xylan. Delta xki1 displayed an interesting molecular phenotype as it over-expressed other PCP genes as well as genes encoding (hemi-) cellulolytic enzymes. However, neither Delta xlr1 nor Delta xki1 showed significant differences in their pathogeny on rice and barley compared to the wild type, suggesting that p-xylose catabolism is not required for fungal growth in infected leaves. (C) 2013 Elsevier Inc. All rights

BACKGROUND: L-arabitol dehydrogenase (LAD) and xylitol dehydrogenase (XDH) are involved in the degradation of L-arabinose and D-xylose, which are among the most abundant monosaccharides on earth. Previous data demonstrated that LAD and XDH not only differ in the activity on their biological substrate, but also that only XDH has significant activity on D-sorbitol and may therefore be more closely related to D-sorbitol dehydrogenases (SDH). In this study we aimed to identify residues involved in the difference in substrate specificity. RESULTS: Phylogenetic analysis demonstrated that LAD, XDH and SDH form 3 distinct groups of the family of dehydrogenases containing an Alcohol dehydrogenase GroES-like domain (pfam08240) and likely have evolved from a common ancestor. Modelling of LadA and XdhA of the saprobic fungus Aspergillus niger on human SDH identified two residues in LadA (M70 and Y318), that may explain the absence of activity on D-sorbitol. While introduction of the mutation M70F in LadA of A. niger resulted in a nearly complete enzyme inactivation, the Y318F resulted in increased activity for L-arabitol and xylitol. Moreover, the affinity for D-sorbitol was increased in this mutant. CONCLUSION: These data demonstrates that Y318 of LadA contributes significantly to the substrate specificity difference between LAD and XDH/SDH., BACKGROUND: L-arabitol dehydrogenase (LAD) and xylitol dehydrogenase (XDH) are involved in the degradation of L-arabinose and D-xylose, which are among the most abundant monosaccharides on earth. Previous data demonstrated that LAD and XDH not only differ in the activity on their biological substrate, but also that only XDH has significant activity on D-sorbitol and may therefore be more closely related to D-sorbitol dehydrogenases (SDH). In this study we aimed to identify residues involved in the difference in substrate specificity. RESULTS: Phylogenetic analysis demonstrated that LAD, XDH and SDH form 3 distinct groups of the family of dehydrogenases containing an Alcohol dehydrogenase GroES-like domain (pfam08240) and likely have evolved from a common ancestor. Modelling of LadA and XdhA of the saprobic fungus Aspergillus niger on human SDH identified two residues in LadA (M70 and Y318), that may explain the absence of activity on D-sorbitol. While introduction of the mutation M70F in LadA of A. niger resulted in a nearly complete enzyme inactivation, the Y318F resulted in increased activity for L-arabitol and xylitol. Moreover, the affinity for D-sorbitol was increased in this mutant. CONCLUSION: These data demonstrates that Y318 of LadA contributes significantly to the substrate specificity difference between LAD and XDH/SDH.

BACKGROUND: L-arabitol dehydrogenase (LAD) and xylitol dehydrogenase (XDH) are involved in the degradation of L-arabinose and D-xylose, which are among the most abundant monosaccharides on earth. Previous data demonstrated that LAD and XDH not only differ in the activity on their biological substrate, but also that only XDH has significant activity on D-sorbitol and may therefore be more closely related to D-sorbitol dehydrogenases (SDH). In this study we aimed to identify residues involved in the difference in substrate specificity. RESULTS: Phylogenetic analysis demonstrated that LAD, XDH and SDH form 3 distinct groups of the family of dehydrogenases containing an Alcohol dehydrogenase GroES-like domain (pfam08240) and likely have evolved from a common ancestor. Modelling of LadA and XdhA of the saprobic fungus Aspergillus niger on human SDH identified two residues in LadA (M70 and Y318), that may explain the absence of activity on D-sorbitol. While introduction of the mutation M70F in LadA of A. niger resulted in a nearly complete enzyme inactivation, the Y318F resulted in increased activity for L-arabitol and xylitol. Moreover, the affinity for D-sorbitol was increased in this mutant. CONCLUSION: These data demonstrates that Y318 of LadA contributes significantly to the substrate specificity difference between LAD and XDH/SDH., BACKGROUND: L-arabitol dehydrogenase (LAD) and xylitol dehydrogenase (XDH) are involved in the degradation of L-arabinose and D-xylose, which are among the most abundant monosaccharides on earth. Previous data demonstrated that LAD and XDH not only differ in the activity on their biological substrate, but also that only XDH has significant activity on D-sorbitol and may therefore be more closely related to D-sorbitol dehydrogenases (SDH). In this study we aimed to identify residues involved in the difference in substrate specificity. RESULTS: Phylogenetic analysis demonstrated that LAD, XDH and SDH form 3 distinct groups of the family of dehydrogenases containing an Alcohol dehydrogenase GroES-like domain (pfam08240) and likely have evolved from a common ancestor. Modelling of LadA and XdhA of the saprobic fungus Aspergillus niger on human SDH identified two residues in LadA (M70 and Y318), that may explain the absence of activity on D-sorbitol. While introduction of the mutation M70F in LadA of A. niger resulted in a nearly complete enzyme inactivation, the Y318F resulted in increased activity for L-arabitol and xylitol. Moreover, the affinity for D-sorbitol was increased in this mutant. CONCLUSION: These data demonstrates that Y318 of LadA contributes significantly to the substrate specificity difference between LAD and XDH/SDH.

Up to now it has not been possible to reliably cross-calibrate dual-energy X-ray absorptiometry (DXA) densitometry equipment made by different manufacturers so that a measurement made on an individual subject can be expressed in the units used with a different type of machine. Manufacturers have adopted various procedures for edge detection and calibration, producing various normal ranges which are specific to each individual manufacturer's brand of machine. In this study we have used the recently described European Spine Phantom (ESP, prototype version), which contains three semi-anthropomorphic "vertebrae" of different densities made of simulated cortical and trabecular bone, to calibrate a range of DXA densitometers and quantitative computed tomography (QCT) equipment used in the measurement of trabecular bone density of the lumbar vertebrae. Three brands of QCT equipment and three brands of DXA equipment were assessed. Repeat measurements were made to assess machine stability. With the large majority of machines which proved stable, mean values were obtained for the measured low, medium and high density vertebrae respectively. In the case of the QCT equipment these means were for the trabecular bone density, and in the case of the DXA equipment for vertebral body bone density in the posteroanterior projection. All DXA machines overestimated the projected area of the vertebral bodies by incorporating variable amounts of transverse process. In general, the QCT equipment gave measured values which were close to the specified values for trabecular density, but there were substantial differences from the specified values in the results provided by the three DXA brands. For the QCT and Norland DXA machines (posteroanterior view), the relationships between specified densities and observed densities were found to be linear, whereas for the other DXA equipment (posteroanterior view), slightly curvilinear, exponential fits were found to be necessary to fit the plots of ob