title: Characterization of two distinct subfamilies of SUN-domain proteins in Arabidopsis and their interactions with the novel KASH-domain protein AtTIK.
abstract: SUN-domain proteins belong to a gene family including classical Cter-SUN and mid-SUN subfamilies differentiated by the position of the SUN domain within the protein. Although present in animal and plant species, mid-SUN proteins have so far remained poorly described. Here, we used a combination of genetics, yeast two-hybrid and in planta transient expression methods to better characterize the SUN family in Arabidopsis thaliana. First, we validated the mid-SUN protein subfamily as a monophyletic group conserved from yeast to plant. Arabidopsis Cter-SUN (AtSUN1 and AtSUN2) and mid-SUN (AtSUN3 and AtSUN4) proteins expressed as fluorescent protein fusions are membrane-associated and localize to the nuclear envelope (NE) and endoplasmic reticulum. However, only the Cter-SUN subfamily is enriched at the NE. We investigated interactions in and between members of the two subfamilies and identified the coiled-coil domain as necessary for mediating interactions. The functional significance of the mid-SUN subfamily was further confirmed in mutant plants as essential for early seed development and involved in nuclear morphology. Finally, we demonstrated that both subfamilies interact with the KASH domain of AtWIP1 and identified a new root-specific KASH-domain protein, AtTIK. AtTIK localizes to the NE and affects nuclear morphology. Our study indicates that Arabidopsis Cter-SUN and mid-SUN proteins are involved in a complex protein network at the nuclear membranes, reminiscent of the LInker of Nucleoskeleton and Cytoskeleton (LINC) complex found in other kingdoms.
authors.affiliation: Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK.
authors.forename: Katja
authors.initials: K
authors.lastname: Graumann
authors.affiliation: UMR CNRS 6293 INSERM U 1103 Clermont Université, GReD, 24 Avenue des Landais, BP80026 63171 Aubière Cedex, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Vanrobays
authors.affiliation: UMR CNRS 6293 INSERM U 1103 Clermont Université, GReD, 24 Avenue des Landais, BP80026 63171 Aubière Cedex, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Tutois
authors.affiliation: UMR CNRS 6293 INSERM U 1103 Clermont Université, GReD, 24 Avenue des Landais, BP80026 63171 Aubière Cedex, France.
authors.forename: Aline V
authors.initials: AV
authors.lastname: Probst
authors.affiliation: Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK.
authors.forename: David E
authors.initials: DE
authors.lastname: Evans
authors.affiliation: UMR CNRS 6293 INSERM U 1103 Clermont Université, GReD, 24 Avenue des Landais, BP80026 63171 Aubière Cedex, France christophe.tatout@univ-bpclermont.fr.
authors.forename: Christophe
authors.initials: C
authors.lastname: Tatout
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D008969:Molecular Sequence Data; D005810:Multigene Family; D009685:Nuclear Envelope / Q000378:metabolism; D010802:Phylogeny; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D011485:Protein Binding; D060066:Protein Interaction Maps; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D013329:Structure-Activity Relationship
chemical_list: D029681:Arabidopsis Proteins
keywords: KASH domain; LINC complex; SUN domain.; mid SUN; nuclear envelope; protein interactions