Physiological Functions of the Cello-Oligosaccharides Binding CebE in the Pathogenic Streptomyces sp. AMCC400023.

Potato common scab, an economically important disease worldwide, is caused by pathogenic Streptomyces strains mainly through the effects of thaxtomin. The cello-oligosaccharides binding protein CebE is proposed as a gateway to the pathogenic development of Streptomyces scabiei . In this study, two functional CebE encoding genes, GEO5601 and GEO7671 , were identified in pathogenic Streptomyces sp. AMCC400023. With a higher binding affinity towards signal molecules, the deletion of GEO5601 severely impaired thaxtomin-producing capacity and reduced the strain's pathogenicity. Transcriptional analysis confirmed that CebE 5601 is also responsible for the import and provision of carbon sources for cell growth. With lower binding affinity, the pathogenicity island (PAI)-localized CebE 7671 may assume a new function of mediating the biological process of sporulation, given the significantly impaired formation of Δ GEO7671 spores. The mechanisms of action of CebE proteins unraveled in Streptomyces sp. AMCC400023 will help pave the way for more effective prevention of the potato common scab disease.