Pectobacterium atrosepticum KDPG aldolase, Eda, participates in the Entner–Doudoroff pathway and independently inhibits expression of virulence determinants

Pectobacterium carotovorum has an incomplete Entner–Doudoroff (ED) pathway, including enzyme 2‐keto‐3‐deoxy‐6‐phosphogluconate aldolase (Eda) but lacking phosphogluconate dehydratase (Edd), while P. atrosepticum (Pba) has a complete pathway. To understand the role of the ED pathway in Pectobacterium infection, mutants of these two key enzymes, Δeda and Δedd, were constructed in Pba SCRI1039. Δeda exhibited significant decreased virulence on potato tubers and colonization in planta and was greatly attenuated in pectinase activity and the ability to use pectin breakdown products, including polygalacturonic acid (PGA) and galacturonic acid. These reduced phenotypes were restored following complementation with an external vector expressing eda. Quantitative reverse transcription PCR analysis revealed that expression of the pectinase genes pelA, pelC, pehN, pelW, and pmeB in Δeda cultured in pyruvate, with or without PGA, was significantly reduced compared to the wild type, while genes for virulence regulators (kdgR, hexR, hexA, and rsmA) remained unchanged. However, Δedd showed similar phenotypes to the wild type. To our knowledge, this is the first demonstration that disruption of eda has a feedback effect on inhibiting pectin degradation and that Eda is involved in building the arsenal of pectinases needed during infection by Pectobacterium.