Abstract

Colletotrichum lindemuthianum is the etiological agent of anthracnose, one of the main diseases of bean (Phaseolus vulgaris). In this study, the complete cDNAs of two endo-β-1,4-xylanase genes (xyl1) from non-pathogenic (0) and pathogenic (1472) races of C. lindemuthianum were isolated and characterized. To get an insight into the role of endo-β-1,4-xylanases in their different lifestyles, xyl1 gene expression and enzyme activity in mycelia of both races grown in the presence of xylan or P. vulgaris cell walls were investigated. The xyl1 sequence analysis and Clustal alignment revealed the characteristic elements of genes coding for endo-β-1,4-xylanases of the GH11 family. The growth of the two races with glucose as the sole carbon source showed both basal transcription levels of xyl1 and endoxylanase activity. When glucose was substituted with xylan or plant cell walls, xyl1 transcription, and enzyme activity significantly increased in race 1472 as compared to race 0. The pathogenic race degraded xylan faster and grew better than the non-pathogenic counterpart. Seemingly, the regulation of xylanolytic gene expression, enzyme production and the nature of the assimilatory carbon substrates processed by these organisms play a determinant role in their lifestyle. Phylogenetic analyses of XYL1 and endo-β-1,4-xylanases from other fungi revealed a diversification process and separation of proteins from the same fungal species into different lineages.

Key words: Colletotrichum lindemuthianum, Phaseolus vulgaris, endo-β-1,4-xylanase, gene expression, phylogeny.