title: PETAL LOSS, a trihelix transcription factor that represses growth in Arabidopsis thaliana, binds the energy-sensing SnRK1 kinase AKIN10.
abstract: Organogenesis in plants involves differential growth. Rapidly growing primordia are distinguished from the meristem and each other by slower growing boundaries. PETAL LOSS (PTL) is a trihelix transcription factor of Arabidopsis that represses growth in boundaries between newly arising sepals. To identify partners involved in this growth limitation, a young inflorescence cDNA library was screened by yeast two-hybrid technology with PTL as bait. The most frequent prey identified was AKIN10, the catalytic α-subunit of the Snf1-related kinase1 (SnRK1). Interaction was mapped to the C-terminal (non-kinase) half of AKIN10 and the N-terminal portion of PTL. Binding of PTL was specific to AKIN10 as there was little binding to the related AKIN11. The interaction was confirmed by co-immunoprecipitation in vitro. Fluorescently tagged products of 35S:YFP-AKIN10 and 35S:CFP-PTL also interacted when transiently expressed together in leaf cells of Nicotiana benthamiana. In this case, most of the cytoplasmic AKIN10 was preferentially moved to the nucleus where PTL accumulated, possibly because a nuclear export sequence in AKIN10 was now masked. During these experiments, we observed that AKIN10 could variably accumulate in the Golgi, shown by its co-localization with a tagged Golgi marker and through its dispersal by brefeldin A. Tests of phosphorylation of PTL by AKIN10 gave negative results. The functional significance of the PTL-AKIN10 interaction remains open, although a testable hypothesis is that AKIN10 senses lower energy levels in inter-sepal zones and, in association with PTL, promotes reduced cell division.
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Vic. 3800, Australia.
authors.forename: Martin
authors.initials: M
authors.lastname: O'Brien
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Vic. 3800, Australia.
authors.forename: Ruth N
authors.initials: RN
authors.lastname: Kaplan-Levy
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Vic. 3800, Australia.
authors.forename: Tezz
authors.initials: T
authors.lastname: Quon
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Vic. 3800, Australia.
authors.forename: Pia G
authors.initials: PG
authors.lastname: Sappl
authors.affiliation: School of Biological Sciences, Monash University, Melbourne, Vic. 3800, Australia david.smyth@monash.edu.
authors.forename: David R
authors.initials: DR
authors.lastname: Smyth
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D017346:Protein Serine-Threonine Kinases; D014157:Transcription Factors; C528401:PTL protein, Arabidopsis; C531469:At3g01090 protein, Arabidopsis
keywords: AKIN10; Arabidopsis; Golgi; PETAL LOSS; SnRK1; transcription factor; trihelix.