title: Cell-Type-Specific Cytokinin Distribution within the Arabidopsis Primary Root Apex.
abstract: Cytokinins (CKs) play a crucial role in many physiological and developmental processes at the levels of individual plant components (cells, tissues, and organs) and by coordinating activities across these parts. High-resolution measurements of intracellular CKs in different plant tissues can therefore provide insights into their metabolism and mode of action. Here, we applied fluorescence-activated cell sorting of green fluorescent protein (GFP)-marked cell types, combined with solid-phase microextraction and an ultra-high-sensitivity mass spectrometry (MS) method for analysis of CK biosynthesis and homeostasis at cellular resolution. This method was validated by series of control experiments, establishing that protoplast isolation and cell sorting procedures did not greatly alter endogenous CK levels. The MS-based method facilitated the quantification of all the well known CK isoprenoid metabolites in four different transgenic Arabidopsis thaliana lines expressing GFP in specific cell populations within the primary root apex. Our results revealed the presence of a CK gradient within the Arabidopsis root tip, with a concentration maximum in the lateral root cap, columella, columella initials, and quiescent center cells. This distribution, when compared with previously published auxin gradients, implies that the well known antagonistic interactions between the two hormone groups are cell type specific.
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Ioanna
authors.identifier: http://orcid.org/0000-0001-9053-2788
authors.initials: I
authors.lastname: Antoniadi
authors.affiliation: Laboratory of Growth Regulators and Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
authors.forename: Lenka
authors.identifier: http://orcid.org/0000-0003-2537-4933
authors.initials: L
authors.lastname: Plačková
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
authors.forename: Biljana
authors.identifier: http://orcid.org/0000-0002-0929-0791
authors.initials: B
authors.lastname: Simonovik
authors.affiliation: Laboratory of Growth Regulators and Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
authors.forename: Karel
authors.initials: K
authors.lastname: Doležal
authors.affiliation: Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Colin
authors.identifier: http://orcid.org/0000-0001-6635-1418
authors.initials: C
authors.lastname: Turnbull
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
authors.forename: Karin
authors.identifier: http://orcid.org/0000-0003-2901-189X
authors.initials: K
authors.lastname: Ljung
authors.affiliation: Laboratory of Growth Regulators and Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic novako@ueb.cas.cz.
authors.forename: Ondřej
authors.identifier: http://orcid.org/0000-0003-3452-0154
authors.initials: O
authors.lastname: Novák
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D001692:Biological Transport; D002469:Cell Separation; D003583:Cytokinins / Q000378:metabolism*; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D018519:Meristem / Q000378:metabolism; D055442:Metabolome; D008904:Miniaturization; D009928:Organ Specificity; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism; D052616:Solid Phase Extraction
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D049452:Green Fluorescent Proteins