title: Salicylic acid mediates the reduced growth of lignin down-regulated plants.
abstract: 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.
authors: Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA.
authors: Lina
authors: L
authors: Gallego-Giraldo
authors: Luis
authors: L
authors: Escamilla-Trevino
authors: Lisa A
authors: LA
authors: Jackson
authors: Richard A
authors: RA
authors: Dixon
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics; D056804:Biofuels; D002396:Catechols / Q000737:chemistry; D003080:Cold Temperature; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D008031:Lignin / Q000737:chemistry*; D000455:Medicago sativa / Q000187:drug effects / Q000235:genetics; D010368:Pectins / Q000737:chemistry; D018521:Plant Physiological Phenomena / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D020156:Salicylic Acid / Q000737:chemistry / Q000494:pharmacology*; D015398:Signal Transduction; D013696:Temperature
chemical_list: D056804:Biofuels; D002396:Catechols; D012333:RNA, Messenger; D010368:Pectins; D008031:Lignin; C034221:catechol; D020156:Salicylic Acid