Growth-defence trade-off in rice: Fast-growing and acquisitive genotypes have lower expression of genes involved in immunity
de Tombeur, Felix | Pélissier, Rémi | Shihan, Ammar | Rahajaharilaza, Koloina | Fort, Florian | Mahaut, Brigitte | Lemoine, Taïna | Thorne, Sarah J. | Hartley, Sue E. | Luquet, Delphine | Fabre, Denis | Lambers, Hans | Morel, Jean-Benoit | Ballini, Elsa | Violle, Cyrille
Plant ecologists and molecular biologists have long considered the hypothesis of a trade-off between plant growth and defence separately. In particular, how genes thought to control the growth-defence trade-off at the molecular level relate with trait-based frameworks in functional ecology, such as the slow-fast plant economics spectrum, is unknown. We grew 49 phenotypically diverse rice genotypes in pots under optimal conditions, and we measured growth-related functional traits and the constitutive expression of 11 genes involved in plant defence. We also quantified the concentration of silicon (Si) in leaves to estimate silica-based defences. Rice genotypes were aligned along a slow-fast continuum, with fast-growing, early-flowering genotypes vs late-flowering, slow-growing genotypes. Leaf dry matter content and leaf Si concentrations were not aligned with this axis and negatively correlated with each other. Live-fast genotypes exhibited greater expression of OsNPR1, a regulator of the salicylic acid pathway that promotes plant defence while suppressing plant growth. These genotypes also exhibited greater expression of SPL7 and GH3.2 that are also involved in both stress resistance and growth. Our results do not support the hypothesis of a growth-defence trade-off when leaf Si and LDMC are considered, but they do when hormonal pathway genes are considered. We demonstrate the benefits of combining ecological and molecular approaches to elucidate the growth-defence trade-off, opening new avenues for plant breeding and crop science.
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