Structure-function relationship of a citrus salicylate methylesterase and role of salicylic acid in citrus canker resistance

Salicylic acid (SA) and its methyl ester, methyl salicylate (MeSA) are well known inducers of local and systemic plant defense responses, respectively. MeSA is a major mediator of systemic acquired resistance (SAR) and its conversion back into SA is thought to be required for SAR. In many plant spec...

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Published in:Scientific reports 2019-03, Vol.9 (1), p.3901-3901, Article 3901
Main Authors: Lima Silva, Caio Cesar de, Shimo, Hugo Massayoshi, de Felício, Rafael, Mercaldi, Gustavo Fernando, Rocco, Silvana Aparecida, Benedetti, Celso Eduardo
Format: Article
Language:English
Subjects:
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38/39
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45/77
631/449/1741
631/449/2661/2666
82/16
82/80
82/83
Amino acids
Canker
Citrus sinensis
Enzymatic activity
Enzymes
Fruits
Gene polymorphism
Humanities and Social Sciences
Molecular modelling
multidisciplinary
Plant species
Salicylic acid
Science
Science (multidisciplinary)
Structure-function relationships
Tobacco
Xanthomonas citri
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Summary:Salicylic acid (SA) and its methyl ester, methyl salicylate (MeSA) are well known inducers of local and systemic plant defense responses, respectively. MeSA is a major mediator of systemic acquired resistance (SAR) and its conversion back into SA is thought to be required for SAR. In many plant species, conversion of MeSA into SA is mediated by MeSA esterases of the SABP2 family. Here we show that the Citrus sinensis SABP2 homologue protein CsMES1 catalyzes the hydrolysis of MeSA into SA. Molecular modeling studies suggest that CsMES1 shares the same structure and SA-binding mode with tobacco SABP2. However, an amino acid polymorphism in the active site of CsMES1-related proteins suggested an important role in enzyme regulation. We present evidence that the side chain of this polymorphic residue directly influences enzyme activity and SA binding affinity in CsMES proteins. We also show that SA and CsMES1 transcripts preferentially accumulate during the incompatible interaction between Xanthomonas aurantifolii pathotype C and sweet orange plants. Moreover, we demonstrate that SA and MeSA inhibited citrus canker caused by Xanthomonas citri , whereas an inhibitor of CsMES1 enhanced canker formation, suggesting that CsMES1 and SA play a role in the local defense against citrus canker bacteria.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-019-40552-3