Xlr1 is involved in the transcriptional control of the pentose catabolic pathway, but not hemi-cellulolytic enzymes in Magnaporthe oryzae

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• 作者：Evy Battaglia ; Sylvia Klaubauf ; Julie Vallet ; Cecile Ribot ; Marc-Henri Lebrun ; Ronald P. de Vries
• 关键词：Pentose catabolism ; Magnaporthe oryzae ; XlnR ; Xylanase regulator ; Arabinoxylan ; Hemicellulose degradation
• 刊名：Fungal Genetics and Biology
• 出版年：2013
• 出版时间：August, 2013
• 年：2013
• 卷：57
• 期：Complete
• 页码：76-84
• 全文大小：1388 K

文摘

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 ¦¤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 ¦¤xlr1 strain on D-xylose and L-arabinose. However, there was no significant difference in xylanolytic and cellulolytic enzyme activities between the ¦¤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. ¦¤xki1 displayed an interesting molecular phenotype as it over-expressed other PCP genes as well as genes encoding (hemi-) cellulolytic enzymes. However, neither ¦¤xlr1 nor ¦¤xki1 showed significant differences in their pathogeny on rice and barley compared to the wild type, suggesting that D-xylose catabolism is not required for fungal growth in infected leaves.