To grow or defend? Low red: Far-red ratios reduce jasmonate sensitivity in Arabidopsis seedlings by promoting DELLA degradation and increasing JAZ10 stability

Abstract

• How plants balance resource allocation between growth and defense under conditions of competitive stress is a key question in plant biology. Low red: far-red (R: FR) ratios, which signal a high risk of competition in plant canopies, repress jasmonate-induced defense responses. The mechanism of this repression is not well understood. We addressed this problem in Arabidopsis by investigating the role of DELLA and JASMONATE ZIM domain (JAZ) proteins. • We showed that a quintuple della mutant and a phyB mutant were insensitive to jasmonate for several physiological readouts. Inactivation of the photoreceptor phyB by low R: FR ratios rapidly reduced DELLA protein abundance, and the inhibitory effect of FR on jasmonate signaling wasmissing in the gai-1 mutant,which encodes a stable version of the GAI DELLA protein. • We also demonstrated that low R: FR ratios and the phyB mutation stabilized the protein JAZ10. Furthermore, we demonstrated that JAZ10 was required for the inhibitory effect of low R: FR on jasmonate responses, and that the jaz10 mutation restored jasmonate sensitivity to the phyB mutant. • We conclude that, under conditions of competition for light, plants redirect resource allocation from defense to rapid elongation by promoting DELLA degradation and enhancing JAZ10 stability.