title: Allelic polymorphism of GIGANTEA is responsible for naturally occurring variation in circadian period in Brassica rapa.
abstract: GIGANTEA (GI) was originally identified by a late-flowering mutant in Arabidopsis, but subsequently has been shown to act in circadian period determination, light inhibition of hypocotyl elongation, and responses to multiple abiotic stresses, including tolerance to high salt and cold (freezing) temperature. Genetic mapping and analysis of families of heterogeneous inbred lines showed that natural variation in GI is responsible for a major quantitative trait locus in circadian period in Brassica rapa. We confirmed this conclusion by transgenic rescue of an Arabidopsis gi-201 loss of function mutant. The two B. rapa GI alleles each fully rescued the delayed flowering of Arabidopsis gi-201 but showed differential rescue of perturbations in red light inhibition of hypocotyl elongation and altered cold and salt tolerance. The B. rapa R500 GI allele, which failed to rescue the hypocotyl and abiotic stress phenotypes, disrupted circadian period determination in Arabidopsis. Analysis of chimeric B. rapa GI alleles identified the causal nucleotide polymorphism, which results in an amino acid substitution (S264A) between the two GI proteins. This polymorphism underlies variation in circadian period, cold and salt tolerance, and red light inhibition of hypocotyl elongation. Loss-of-function mutations of B. rapa GI confer delayed flowering, perturbed circadian rhythms in leaf movement, and increased freezing and increased salt tolerance, consistent with effects of similar mutations in Arabidopsis. Collectively, these data suggest that allelic variation of GI-and possibly of clock genes in general-offers an attractive target for molecular breeding for enhanced stress tolerance and potentially for improved crop yield.
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3563;
authors.forename: Qiguang
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3563;
authors.forename: Ping
authors.initials: P
authors.lastname: Lou
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3563;
authors.forename: Victor
authors.initials: V
authors.lastname: Hermand
authors.affiliation: Division of Applied Life Science (BK21 Program), Plant Molecular Biology and Biotechnology Research Center and Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju 660-701, South Korea; and.
authors.forename: Rashid
authors.initials: R
authors.lastname: Aman
authors.affiliation: Division of Applied Life Science (BK21 Program), Plant Molecular Biology and Biotechnology Research Center and Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju 660-701, South Korea; and.
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Division of Applied Life Science (BK21 Program), Plant Molecular Biology and Biotechnology Research Center and Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju 660-701, South Korea; and.
authors.forename: Dae-Jin
authors.initials: DJ
authors.lastname: Yun
authors.affiliation: Division of Applied Life Science (BK21 Program), Plant Molecular Biology and Biotechnology Research Center and Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju 660-701, South Korea; and.
authors.forename: Woe Yeon
authors.initials: WY
authors.lastname: Kim
authors.affiliation: Departments of Botany and.
authors.forename: Matti Juhani
authors.initials: MJ
authors.lastname: Salmela
authors.affiliation: Departments of Botany and.
authors.forename: Brent E
authors.initials: BE
authors.lastname: Ewers
authors.affiliation: Departments of Botany and Molecular Biology, University of Wyoming, Laramie, WY 82071.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Weinig
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3563;
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Khan
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3563;
authors.forename: D Loring P
authors.initials: DL
authors.lastname: Schaible
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3563; c.robertson.mcclung@dartmouth.edu.
authors.forename: C Robertson
authors.initials: CR
authors.lastname: McClung
mesh_terms: D000483:Alleles; D001483:Base Sequence; D001937:Brassica / Q000235:genetics*; D002874:Chromosome Mapping; D002940:Circadian Rhythm; D005091:Exons; D035264:Flowers; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018546:Hypocotyl / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology*; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci; D036226:Seedlings; D013696:Temperature; D019076:Transgenes
chemical_list: D010940:Plant Proteins
keywords: abiotic stress tolerance; circadian clock; flowering time; hypocotyl elongation; natural variation