title: Promotion of Germination Using Hydroxamic Acid Inhibitors of 9-cis-Epoxycarotenoid Dioxygenase.
abstract: Abscisic acid (ABA) inhibits seed germination and the regulation of ABA biosynthesis has a role in maintenance of seed dormancy. The key rate-limiting step in ABA biosynthesis is catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). Two hydroxamic acid inhibitors of carotenoid cleavage dioxygenase (CCD), D4 and D7, previously found to inhibit CCD and NCEDin vitro, are shown to have the novel property of decreasing mean germination time of tomato (Solanum lycopersicumL.) seeds constitutively overexpressingLeNCED1. Post-germination, D4 exhibited no negative effects on tomato seedling growth in terms of height, dry weight, and fresh weight. Tobacco (Nicotiana tabacumL.) seeds containing a tetracycline-inducibleLeNCED1transgene were used to show that germination could be negatively and positively controlled through the chemical induction of gene expression and the chemical inhibition of the NCED protein: application of tetracycline increased mean germination time and delayed hypocotyl emergence in a similar manner to that observed when exogenous ABA was applied and this was reversed by D4 whenNCEDexpression was induced at intermediate levels. D4 also improved germination in lettuce (Lactuca sativaL.) seeds under thermoinhibitory temperatures and in tomato seeds imbibed in high osmolarity solutions of polyethylene glycol. D4 reduced ABA and dihydrophaseic acid accumulation in tomato seeds overexpressingLeNCED1and reduced ABA accumulation in wild type tomato seeds imbibed on polyethylene glycol. The evidence supports a mode of action of D4 through NCED inhibition, and this molecule provides a lead compound for the design of NCED inhibitors with greater specificity and potency.
authors.affiliation: School of Life Sciences, University of Warwick Coventry, UK.
authors.forename: Sajjad Z
authors.initials: SZ
authors.lastname: Awan
authors.affiliation: School of Life Sciences, University of WarwickCoventry, UK; Cranfield Soil and Agrifood Institute, Cranfield UniversityCranfield, UK.
authors.forename: Jake O
authors.initials: JO
authors.lastname: Chandler
authors.affiliation: Department of Chemistry, University of Warwick Coventry, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Harrison
authors.affiliation: School of Life Sciences, University of Warwick Coventry, UK.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Sergeant
authors.affiliation: Department of Chemistry, University of Warwick Coventry, UK.
authors.forename: Timothy D H
authors.initials: TD
authors.lastname: Bugg
authors.affiliation: Cranfield Soil and Agrifood Institute, Cranfield University Cranfield, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thompson
keywords: 9-cis-epoxycarotenoid dioxygenase; abscisic acid; chemical genetics; dormancy; hydroxamic acid; seed germination