Root-Secreted Malic Acid Recruits Beneficial Soil Bacteria1[C][W][OA]

By T. Rudrappa, Kirk Czymmek, Paul W. Pare, H. Bais. Plant Physiology, 2008

935 citations recorded by the source corpus.

Beneficial soil bacteria confer immunity against a wide range of foliar diseases by activating plant defenses, thereby reducing a plant's susceptibility to pathogen attack. Although bacterial signals have been identified that activate these plant defenses, plant metabolites that elicit rhizobacterial responses have not been demonstrated. Here, we provide biochemical evidence that the tricarboxylic acid cycle intermediate l-malic acid (MA) secreted from roots of Arabidopsis (Arabidopsis thaliana) selectively signals and recruits the beneficial rhizobacterium Bacillus subtilis FB17 in a dose-dependent manner. Root secretions of l-MA are induced by the foliar pathogen Pseudomonas syringae pv tomato (Pst DC3000) and elevated levels of l-MA promote binding and biofilm formation of FB17 on Arabidopsis roots. The demonstration that roots selectively secrete l-MA and effectively signal beneficial rhizobacteria establishes a regulatory role of root metabolites in recruitment of beneficial microbes, as well as underscores the breadth and sophistication of plant-microbial interactions.

Subfields: Plant Science

View Paper: https://www.semanticscholar.org/paper/699f4e30c87a6e5effade413426f574d06ca19a9

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1. C. Pieterse
2. P. Bakker
3. L. C. van Loon
4. A. Sessitsch
5. J. Raaijmakers
6. R. Mendes
7. S. Compant
8. J. Chaparro

Citations in the corpus

• Feed Your Friends: Do Plant Exudates Shape the Root Microbiome? (2018, background): “The few characterized transporters involved in exudation are essential for the transport of specific compounds (Figure 2 [636_TD$DIFF]and Box 2) [31,80], and are presented in Table 1.”
• Root Exudation: The Ecological Driver of Hydrocarbon Rhizoremediation (2016, background): “[204] demonstrated that released-malic acid allows the recruitment of Bacillus subtilis (PGPR).”
• Manipulating the soil microbiome to increase soil health and plant fertility (2012, background): “For example, exogenous application of the Bacillus subtilis-derived elicitor, acetoin (3-hy- droxy-2-butanone), was found to trigger induced systemic resistance (ISR) and protect plants against Pseudomonas syringae pv tomato pathogenesis (Rudrappa et al. 2008).”
• Impact of plant domestication on rhizosphere microbiome assembly and functions (2015, background): “Interestingly, infection of Arabidopsis leaves with Pseudomonas syringae pv tomato induced an increased secretion of malic acid from the roots, promoting the colonization and biofilm formation by strain FB17 (Rudrappa et al. 2008).”
• The convergent evolution of aluminium resistance in plants exploits a convenient currency (2010, background): “Both genes are partly induced by low pH (Kobayashi et al. 2007; Liu et al. 2009) and AtALMT1 is strongly induced by foliar infection with Pseudomonas syringae (Rudrappa et al. 2008).”
• Plant growth-promoting bacteria as inoculants in agricultural soils (2015, background): “Bacillus subtilis FB17, for instance, is attracted by L-malic acid, secreted by the roots of Arabidopsis thaliana infected with the foliar pathogen P. syringae pv tomato (Pst DC3000; Rudrappa et al., 2008).”
• Root Exudation of Phytochemicals in Arabidopsis Follows Specific Patterns That Are Developmentally Programmed and Correlate with Soil Microbial Functions (2013, background): “Sugars serve as ready sources of energy for microbial growth [47], and secondary metabolites, such as those categorized as phenolics in this study, may function as antimicrobials and signaling molecules in the rhizosphere [6,8,48,49].”
• Advances in Elucidating Beneficial Interactions Between Plants, Soil, and Bacteria (2013, background): “…et al., 2011), andArabidopsis roots have been shown to secrete L-malic acid after P. syringae 416 Birgit Mitter et al. pv. tomato DC3000 attack, which attracts beneficial B. subtilis FB17 to colonize plant roots and to further protect plants against subsequent infections (Rudrappa et al., 2008).”