Phosphorylation of p27KIP1 homologs KRP6 and 7 by SNF1‐related protein kinase–1 links plant energy homeostasis and cell proliferation. (13th June 2013)

• Record Type: Journal Article
• Authors: Guérinier, Thomas; Millan, Laurine; Crozet, Pierre; Oury, Céline; Rey, François; Valot, Benoit; Mathieu, Chantal; Vidal, Jean; Hodges, Michael; Thomas, Martine; Glab, Nathalie
• Is Part Of: Plant journal. Volume 75:Number 3(2013:Aug.)
• Page Start: 515
• Page End: 525
• Publication Date: 2013-06-13
• Subjects: Kip‐related protein -- SNF1‐related protein kinase–1 -- cell proliferation -- energy homeostasis -- phosphorylation -- Arabidopsis thaliana; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12218
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: SNF1‐related protein kinase–1 (SnRK1), the plant kinase homolog of mammalian AMP‐activated protein kinase (AMPK), is a sensor that maintains cellular energy homeostasis via control of anabolism/catabolism balance. AMPK‐dependent phosphorylation of p27 KIP 1 affects cell‐cycle progression, autophagy and apoptosis. Here, we show that SnRK1 phosphorylates the Arabidopsis thaliana cyclin‐dependent kinase inhibitor p27 KIP 1 homologs AtKRP6 and AtKRP7, thus extending the role of this kinase to regulation of cell‐cycle progression. AtKRP6 and 7 were phosphorylated in vitro by a recombinant activated catalytic subunit of SnRK1 (AtSnRK1α1). Tandem mass spectrometry and site‐specific mutagenesis identified Thr152 and Thr151 as the phosphorylated residues on AtKRP6‐ and AtKRP7, respectively. AtSnRK1 physically interacts with AtKRP6 in the nucleus of transformed BY–2 tobacco protoplasts, but, in contrast to mammals, the AtKRP6 Thr152 phosphorylation state alone did not modify its nuclear localization. Using a heterologous yeast system, consisting of a cdc28 yeast mutant complemented by A. thaliana CDKA;1, cell proliferation was shown to be abolished by AtKRP6 WT and by the non‐phosphorylatable form AtKRP6 T152A, but not by the phosphorylation‐mimetic form AtKRP6 T152D . Moreover, A. thaliana SnRK1α1/KRP6 double over‐expressor plants showed an attenuated AtKRP6‐associated phenotype (strongly serrated leaves and inability to undergo callogenesis). Furthermore, this severe phenotype was not observed in AtKRP6 T152D over‐expressor plants. Overall, these results establish that the energy sensor AtSnRK1 plays a cardinal role in the control of cell proliferation in A. thaliana plants through inhibition of AtKRP6 biological function by phosphorylation.