Salicylic acid mediates the reduced growth of lignin down-regulated plants

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 51; pp. 20814 - 20819
• Main Authors: Gallego-Giraldo, Lina, Escamilla-Trevino, Luis, Jackson, Lisa A, Dixon, Richard A
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 20.12.2011; National Acad Sciences
• Subjects: Alfalfa; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis thaliana; Biofuels; Biological Sciences; Biosynthesis; Catechols - chemistry; cell walls; Cold Temperature; Down regulation; Enzymes; Flavonoids; Flowers & plants; Gene Expression Regulation, Plant; Genetics; Genotype; gibberellic acid; growth retardation; Hematocrit; Hormones; hydroxycinnamoyltransferase; Lignin; Lignin - chemistry; Medicago sativa; Medicago sativa - drug effects; Medicago sativa - genetics; Pectins - chemistry; Plant growth; Plant growth regulators; Plant Physiological Phenomena - drug effects; Plants; RNA, Messenger - metabolism; salicylic acid; Salicylic Acid - chemistry; Salicylic Acid - pharmacology; Signal Transduction; Temperature; Transgenic plants
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1117873108

Down-regulation of the enzyme hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase (HCT) in thale cress (Arabidopsis thaliana) and alfalfa (Medicago sativa) leads to strongly reduced lignin levels, reduced recalcitrance of cell walls to sugar release, but severe stunting of the plants. Levels of the stress hormone salicylic acid (SA) are inversely proportional to lignin levels and growth in a series of transgenic alfalfa plants in which lignin biosynthesis has been perturbed at different biosynthetic steps. Reduction of SA levels by genetically blocking its formation or causing its removal restores growth in HCT–down-regulated Arabidopsis, although the plants maintain reduced lignin levels. SA-mediated growth inhibition may occur via interference with gibberellic acid signaling or responsiveness. Our data place SA as a central component in growth signaling pathways that either sense flux into the monolignol pathway or respond to secondary cell-wall integrity, and indicate that it is possible to engineer plants with highly reduced cell-wall recalcitrance without negatively impacting growth.