title: Transgenic alteration of ethylene biosynthesis increases grain yield in maize under field drought-stress conditions.
abstract: A transgenic gene-silencing approach was used to modulate the levels of ethylene biosynthesis in maize (Zea mays L.) and determine its effect on grain yield under drought stress in a comprehensive set of field trials. Commercially relevant transgenic events were created with down-regulated ACC synthases (ACSs), enzymes that catalyse the rate-limiting step in ethylene biosynthesis. These events had ethylene emission levels reduced approximately 50% compared with nontransgenic nulls. Multiple, independent transgenic hybrids and controls were tested in field trials at managed drought-stress and rain-fed locations throughout the US. Analysis of yield data indicated that transgenic events had significantly increased grain yield over the null comparators, with the best event having a 0.58 Mg/ha (9.3 bushel/acre) increase after a flowering period drought stress. A (genotype × transgene) × environment interaction existed among the events, highlighting the need to better understand the context in which the down-regulation of ACSs functions in maize. Analysis of secondary traits showed that there was a consistent decrease in the anthesis-silking interval and a concomitant increase in kernel number/ear in transgene-positive events versus nulls. Selected events were also field tested under a low-nitrogen treatment, and the best event was found to have a significant 0.44 Mg/ha (7.1 bushel/acre) yield increase. This set of extensive field evaluations demonstrated that down-regulating the ethylene biosynthetic pathway can improve the grain yield of maize under abiotic stress conditions.
authors.affiliation: DuPont Pioneer, Johnston, IA, USA.
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Habben
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Bao
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Bate
authors.forename: Jason L
authors.initials: JL
authors.lastname: DeBruin
authors.forename: Dennis
authors.initials: D
authors.lastname: Dolan
authors.forename: Darren
authors.initials: D
authors.lastname: Hasegawa
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Helentjaris
authors.forename: Renee H
authors.initials: RH
authors.lastname: Lafitte
authors.forename: Nina
authors.initials: N
authors.lastname: Lovan
authors.forename: Hua
authors.initials: H
authors.lastname: Mo
authors.forename: Kellie
authors.initials: K
authors.lastname: Reimann
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Schussler
mesh_terms: D055864:Droughts; D005030:Ethylenes / Q000096:biosynthesis*; D008190:Lyases / Q000378:metabolism; D009584:Nitrogen / Q000494:pharmacology; D030821:Plants, Genetically Modified; D034622:RNA Interference / Q000187:drug effects; D012639:Seeds / Q000187:drug effects / Q000254:growth & development*; D013312:Stress, Physiological / Q000187:drug effects; D003313:Zea mays / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology
chemical_list: D005030:Ethylenes; C036216:ethylene; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; D009584:Nitrogen
keywords: ACC synthase; drought tolerance; ethylene; grain yield; maize; phytohormone