title: Potassium transporter TRH1 subunits assemble regulating root-hair elongation autonomously from the cell fate determination pathway.
abstract: Trichoblasts of trh1 plants form root-hair initiation sites that fail to undergo tip growth resulting in a tiny root-hair phenotype. TRH1 belongs to Arabidopsis KT/KUP/HAK potassium transporter family controlling root-hair growth and gravitropism. Double mutant combinations between trh1 and root-hair mutants affecting cell fate or root-hair initiation exhibited additive phenotypes, suggesting that TRH1 acts independently and developmentally downstream of root-hair initiation. Bimolecular Fluorescence Complementation (BiFC), upon TRH1-YFP(C) and TRH1-YFP(N) co-transformation into tobacco epidermal cells, led to fluorescence emission indicative of TRH1 subunit homodimerization. Yeast two-hybrid analysis revealed two types of interactions. The hydrophilic segment between the second and the third transmembrane domain extending from residues Q105 to T141 is competent for a relatively weak interaction, whereas the region at the C-terminal beyond the last transmembrane domain, extending from amino acids R565 to A729, strongly self-interacts. These domains likely facilitate the co-assembly of TRH1 subunits forming an active K(+) transport system within cellular membrane structures. The results support the role of TRH1 acting as a convergence point between the developmental root-hair pathway and the environmental/hormonal signaling pathway to preserve auxin homeostasis ensuring plant adaptation in changing environments.
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75,118 55, Athens, Greece. Electronic address: gdaras@aua.gr.
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Daras
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75,118 55, Athens, Greece. Electronic address: srigas@aua.gr.
authors.forename: Stamatis
authors.initials: S
authors.lastname: Rigas
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75,118 55, Athens, Greece. Electronic address: dtsitsekian@aua.gr.
authors.forename: Dikran
authors.initials: D
authors.lastname: Tsitsekian
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75,118 55, Athens, Greece. Electronic address: tiacovides@da.moa.gov.cy.
authors.forename: Tefkros A
authors.initials: TA
authors.lastname: Iacovides
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75,118 55, Athens, Greece. Electronic address: phat@aua.gr.
authors.forename: Polydefkis
authors.initials: P
authors.lastname: Hatzopoulos
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D027961:Potassium-Hydrogen Antiporters; C501258:potassium transporter, Arabidopsis
keywords: Arabidopsis thaliana; KUP/HAK/KT K(+) transporters; Protein interaction; Root hairs; TRH1 assembly