Journal
PLANT JOURNAL
Volume 101, Issue 5, Pages 1103-1117Publisher
WILEY
DOI: 10.1111/tpj.14577
Keywords
phytoalexin; sakuranetin; naringenin; naringenin-7-O-methyltransferase; chemodiversity; chemotype; rice; Oryza sativa; Oryza rufipogon
Categories
Funding
- Strategic International Cooperative Program - Joint Research Type, Metabolomics for a low carbon society from the Japan Science and Technology Agency (JST)
- US National Science Foundation [1139329, 1811965]
- Japan Society for the Promotion of Science (JSPS) KAKENHI [16K07718]
- Grants-in-Aid for Scientific Research [16K07718] Funding Source: KAKEN
- Direct For Biological Sciences
- Division Of Integrative Organismal Sys [1139329] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1811965] Funding Source: National Science Foundation
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Phytoalexins play a pivotal role in plant-pathogen interactions. Whereas leaves of rice (Oryza sativa) cultivar Nipponbare predominantly accumulated the phytoalexin sakuranetin after jasmonic acid induction, only very low amounts accumulated in the Kasalath cultivar. Sakuranetin is synthesized from naringenin by naringenin 7-O-methyltransferase (NOMT). Analysis of chromosome segment substitution lines and backcrossed inbred lines suggested that NOMT is the underlying cause of differential phytoalexin accumulation between Nipponbare and Kasalath. Indeed, both NOMT expression and NOMT enzymatic activity are lower in Kasalath than in Nipponbare. We identified a proline to threonine substitution in Kasalath relative to Nipponbare NOMT as the main cause of the lower enzymatic activity. Expanding this analysis to rice cultivars with varying amounts of sakuranetin collected from around the world showed that NOMT induction is correlated with sakuranetin accumulation. In bioassays with Pyricularia oryzae, Gibberella fujikuroi, Bipolaris oryzae, Burkholderia glumae, Xanthomonas oryzae, Erwinia chrysanthemi, Pseudomonas syringae, and Acidovorax avenae, naringenin was more effective against bacterial pathogens and sakuranetin was more effective against fungal pathogens. Therefore, the relative amounts of naringenin and sakuranetin may provide protection against specific pathogen profiles in different rice-growing environments. In a dendrogram of NOMT genes, those from low-sakuranetin-accumulating cultivars formed at least two clusters, only one of which involves the proline to threonine mutation, suggesting that the low sakuranetin chemotype was acquired more than once in cultivated rice. Strains of the wild rice species Oryza rufipogon also exhibited differential sakuranetin accumulation, indicating that this metabolic diversity predates rice domestication.
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