Bitter and sweet make tomato hard to (b)eat

Yaohua You, Jan A.L. van Kan*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The glycoalkaloid saponin α-tomatine is a tomato-specific secondary metabolite that accumulates to millimolar levels in vegetative tissues and has antimicrobial and antinutritional activity that kills microbial pathogens and deters herbivorous insects. We describe recent insights into the biosynthetic pathway of α-tomatine synthesis and its regulation. We discuss the mode of action of α-tomatine by physically interacting with sterols, thereby disrupting membranes, and how tomato protects itself from its toxic action. Tomato pathogenic microbes can enzymatically hydrolyze, and thereby inactivate, α-tomatine using either of three distinct types of glycosyl hydrolases. We also describe findings that extend well beyond the simple concept of plants producing toxins and pathogens inactivating them. There are reports that toxicity of α-tomatine is modulated by external pH, that α-tomatine can trigger programmed cell death in fungi, that cellular localization matters for the impact of α-tomatine on invading microbes, and that α-tomatine breakdown products generated by microbial hydrolytic enzymes can modulate plant immune responses. Finally, we address a number of outstanding questions that deserve attention in the future.

Original languageEnglish
JournalNew Phytologist
DOIs
Publication statusE-pub ahead of print - 21 Nov 2020

Keywords

  • antimicrobial activity
  • antinutritional activity
  • carbohydrate active enzymes
  • glycoalkaloid
  • membrane sterols
  • Solanum lycopersicum

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