Metabolomics of tomato xylem sap during bacterial wilt reveals Ralstonia solanacearum produces abundant putrescine, a metabolite that accelerates wilt disease

Tiffany M. Lowe-Power, Connor G. Hendrich, Edda von Roepenack-Lahaye, Bin Li, Dousheng Wu, Raka Mitra, Beth L. Dalsing, Patrizia Ricca, Jacinth Naidoo, David Cook, Amy Jancewicz, Patrick Masson, Bart Thomma, Thomas Lahaye, Anthony J. Michael, Caitilyn Allen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

70 Citations (Scopus)

Abstract

Ralstonia solanacearum thrives in plant xylem vessels and causes bacterial wilt disease despite the low nutrient content of xylem sap. We found that R. solanacearum manipulates its host to increase nutrients in tomato xylem sap, enabling it to grow better in sap from infected plants than in sap from healthy plants. Untargeted GC/MS metabolomics identified 22 metabolites enriched in R. solanacearum-infected sap. Eight of these could serve as sole carbon or nitrogen sources for R. solanacearum. Putrescine, a polyamine that is not a sole carbon or nitrogen source for R. solanacearum, was enriched 76-fold to 37 μM in R. solanacearum-infected sap. R. solanacearum synthesized putrescine via a SpeC ornithine decarboxylase. A ΔspeC mutant required≥15 μM exogenous putrescine to grow and could not grow alone in xylem even when plants were treated with putrescine. However, co-inoculation with wildtype rescued ΔspeC growth, indicating R. solanacearum produced and exported putrescine to xylem sap. Intriguingly, treating plants with putrescine before inoculation accelerated wilt symptom development and R. solanacearum growth and systemic spread. Xylem putrescine concentration was unchanged in putrescine-treated plants, so the exogenous putrescine likely accelerated disease indirectly by affecting host physiology. These results indicate that putrescine is a pathogen-produced virulence metabolite.
Original languageEnglish
Pages (from-to)1330-1349
JournalEnvironmental Microbiology
Volume20
Issue number4
Early online date22 Dec 2017
DOIs
Publication statusPublished - Apr 2018

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