title: Effects of conditional IPT-dependent cytokinin overproduction on root architecture of Arabidopsis seedlings.
abstract: Cytokinin (CK) has been known to inhibit primary root elongation and suggested to act as an auxin antagonist in the regulation of lateral root (LR) formation. While the role of auxin in root development has been thoroughly studied, the detailed and overall description of CK effects on root system morphology, particularly that of developing lateral root primordia (LRPs), and hence its role in organogenesis is still in progress. Here we examine the effects of conditional endogenous CK overproduction on root architecture and consider its temporal aspect during the early development of Arabidopsis thaliana. We employed the pOp/LhGR system to induce ectopic ipt overexpression with a glucocorticoid dexamethasone at designated developmental points. The transient CaMV 35S>GR>ipt transactivation greatly enhanced levels of biologically active CKs of zeatin (Z)-type and identified a distinct developmental interval during which primary root elongation is susceptible to increases in endogenous CK production. Long-term CK overproduction inhibited primary root elongation by reducing quantitative parameters of primary root meristem, disturbed a characteristic graded distribution pattern of auxin response in LRPs and impaired their development. Our findings indicate the impact of perturbed endogenous CK on the regulation of asymmetric auxin distribution during LRP development and imply that there is cross-talk between auxin and CK during organogenesis in A. thaliana.
authors.affiliation: Laboratory of Plant Molecular Physiology, Department of Functional Genomics and Proteomics, Institute of Experimental Biology, Masaryk University, Kamenice 5, CZ-62500 Brno, Czech Republic.
authors.forename: Alena
authors.initials: A
authors.lastname: Kuderová
authors.forename: Ivana
authors.initials: I
authors.lastname: Urbánková
authors.forename: Martina
authors.initials: M
authors.lastname: Válková
authors.forename: Jirí
authors.initials: J
authors.lastname: Malbeck
authors.forename: Bretislav
authors.initials: B
authors.lastname: Brzobohaty
authors.forename: Danka
authors.initials: D
authors.lastname: Némethová
authors.forename: Jan
authors.initials: J
authors.lastname: Hejátko
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000033:anatomy & histology* / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D003583:Cytokinins / Q000096:biosynthesis*; D003907:Dexamethasone / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007210:Indoleacetic Acids / Q000378:metabolism; D018519:Meristem / Q000166:cytology / Q000187:drug effects; D018517:Plant Roots / Q000033:anatomy & histology* / Q000166:cytology / Q000187:drug effects / Q000254:growth & development; D018547:Plant Stems / Q000166:cytology / Q000187:drug effects; D036226:Seedlings / Q000033:anatomy & histology* / Q000187:drug effects; D015026:Zeatin / Q000378:metabolism
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D015026:Zeatin; D003907:Dexamethasone; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase