title: Differential control of seed primary dormancy in Arabidopsis ecotypes by the transcription factor SPATULA.
abstract: Freshly matured seeds exhibit primary dormancy, which prevents germination until environmental conditions are favorable. The establishment of dormancy occurs during seed development and involves both genetic and environmental factors that impact on the ratio of two antagonistic phytohormones: abscisic acid (ABA), which promotes dormancy, and gibberellic acid, which promotes germination. Although our understanding of dormancy breakage in mature seeds is well advanced, relatively little is known about the mechanisms involved in establishing dormancy during seed maturation. We previously showed that the SPATULA (SPT) transcription factor plays a key role in regulating seed germination. Here we investigate its role during seed development and find that, surprisingly, it has opposite roles in setting dormancy in Landsberg erecta and Columbia Arabidopsis ecotypes. We also find that SPT regulates expression of five transcription factor encoding genes: ABA-INSENSITIVE4 (ABI4) and ABI5, which mediate ABA signaling; REPRESSOR-OF-GA (RGA) and RGA-LIKE3 involved in gibberellic acid signaling; and MOTHER-OF-FT-AND-TFL1 (MFT) that we show here promotes Arabidopsis seed dormancy. Although ABI4, RGA, and MFT are repressed by SPT, ABI5 and RGL3 are induced. Furthermore, we show that RGA, MFT, and ABI5 are direct targets of SPT in vivo. We present a model in which SPT drives two antagonistic "dormancy-repressing" and "dormancy-promoting" routes that operate simultaneously in freshly matured seeds. Each of these routes has different impacts and this in turn explains the opposite effect of SPT on seed dormancy of the two ecotypes analyzed here.
authors.affiliation: Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5DD, United Kingdom.
authors.forename: Fabián E
authors.initials: FE
authors.lastname: Vaistij
authors.forename: Yinbo
authors.initials: Y
authors.lastname: Gan
authors.forename: Steven
authors.initials: S
authors.lastname: Penfield
authors.forename: Alison D
authors.initials: AD
authors.lastname: Gilday
authors.forename: Anuja
authors.initials: A
authors.lastname: Dave
authors.forename: Zhesi
authors.initials: Z
authors.lastname: He
authors.forename: Eve-Marie
authors.initials: EM
authors.lastname: Josse
authors.forename: Giltsu
authors.initials: G
authors.lastname: Choi
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Halliday
authors.forename: Ian A
authors.initials: IA
authors.lastname: Graham
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018525:Germination / Q000235:genetics / Q000502:physiology; D009154:Mutation; D057445:Plant Dormancy / Q000235:genetics / Q000502:physiology*; D013045:Species Specificity
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; C426006:SPT protein, Arabidopsis
keywords: chromatin immunoprecipitation; phytohormone analyses; transcriptomic analyses