title: Gene expression profiling reveals defined functions of the ATP-binding cassette transporter COMATOSE late in phase II of germination.
abstract: Phase II of germination represents a key developmental stage of plant growth during which imbibed seeds either enter stage III of germination, completing the germination process via radicle protrusion, or remain dormant. In this study, we analyzed the influence of the peroxisomal ATP-binding cassette transporter COMATOSE (CTS) on the postimbibition seed transcriptome of Arabidopsis (Arabidopsis thaliana) and also investigated interactions between gibberellin (GA) and CTS function. A novel method for analysis of transcriptome datasets allowed visualization of developmental signatures of seeds, showing that cts-1 retains the capacity to after ripen, indicating a germination block late in phase II. Expression of the key GA biosynthetic genes GA3ox1 and 2 was greatly reduced in cts seeds and genetic analysis suggested that CTS was epistatic to RGL2, a germination-repressing DELLA protein that is degraded by GA. Comparative analysis of seed transcriptome datasets indicated that specific cohorts of genes were influenced by GA and CTS. CTS function was required for expression of the flavonoid biosynthetic pathway. Confocal imaging demonstrated the exclusive accumulation of flavonoids in the epidermis of wild-type seeds. In contrast, flavonoids were absent from cts and kat2-1 mutant seeds, but accumulated following the application of sucrose, indicating an essential role for beta-oxidation in inducing flavonoid biosynthetic genes. These results demonstrate that CTS functions very late in phase II of germination and that its function is required for the expression of specific gene sets related to an important biochemical pathway associated with seedling establishment and survival.
authors.affiliation: Centro de Genomica, Instituto Valenciano de Investigaciones Agrarias, Valencia, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Carrera
authors.forename: Tara
authors.initials: T
authors.lastname: Holman
authors.forename: Anne
authors.initials: A
authors.lastname: Medhurst
authors.forename: Wendy
authors.initials: W
authors.lastname: Peer
authors.forename: Heike
authors.initials: H
authors.lastname: Schmuths
authors.forename: Steven
authors.initials: S
authors.lastname: Footitt
authors.forename: Frederica L
authors.initials: FL
authors.lastname: Theodoulou
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Holdsworth
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000251:Adenosine Triphosphatases; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D018525:Germination; D017403:In Situ Hybridization; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000502:physiology
chemical_list: D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D012333:RNA, Messenger; D000251:Adenosine Triphosphatases; C456843:At4g39850 protein, Arabidopsis