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"first_pagesettingsOrder Article Reprints Open AccessArticle Limitation of Cytokinin Export to the Shoots by Nucleoside Transporter ENT3 and Its Linkage with Root Elongation in Arabidopsis by Alla Korobova 1,Bulat Kuluev 2,3,Torsten Möhlmann 4,Dmitriy Veselov 1 andGuzel Kudoyarova 1,3,* 1 Laboratory of Plant Physiology, Ufa Institute of Biology, Ufa Federal Research Centre, RAS, 450054 Ufa, Russia 2 Institute of Biochemistry and Genetics, Ufa Federal Research Centre, RAS, 450054 Ufa, Russia 3 Biological Department, Bashkir State University, 450076 Ufa, Russia 4 Department of Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany * Author to whom correspondence should be addressed. Cells 2021, 10(2), 350; https://doi.org/10.3390/cells10020350 Submission received: 18 December 2020 / Revised: 1 February 2021 / Accepted: 6 February 2021 / Published: 8 February 2021 (This article belongs to the Special Issue Local and Systemic Signals of Macronutrient and Water Availability Regulating Root Growth and Development) Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract The trans-membrane carrier AtENT3 is known to transport externally supplied cytokinin ribosides and thus promote uptake by cells. However, its role in distributing either exogenous or endogenous cytokinins within the intact plant has not hitherto been reported. To test this, we used ent3-1 mutant Arabidopsis seedlings in which the gene is not expressed due to a T-DNA insertion, and examined the effect on the concentration and distribution of either endogenous cytokinins or exogenous trans-zeatin riboside applied to the roots. In the mutant, accumulation of endogenous cytokinins in the roots was reduced and capacity to deliver externally supplied trans-zeatin riboside to the shoots was increased suggesting involvement of equilibrative nucleoside (ENT) transporter in the control of cytokinin distribution in the plants. Roots of ent3-1 were longer in the mutant in association with t

"Abstract The decapitated primary root of 3-day-old Alaska pea seedlings has been used as a test system to determine the activities on lateral root formation of six auxins, six cytokinins and several other naturally-occurring compounds. Their effects were assessed on (1) the initiation of lateral root primordia, (2) the emergence of visible lateral roots, and (3) the elongation of these laterals. All the auxins, at the optimum concentration of 10-4M, promoted the initiation of lateral root primordia, and all except 3-indolylpropionic acid inhibited the elongation of the resulting lateral roots. Their effects on the emergence of laterals were small and varied. All the cytokinins, at 10-6M and above, inhibited both the initiation and the emergence of lateral roots, zeatin being the most powerful inhibitor. The emergence process was about twice as sensitive as the initiation of primordia to the presence of cytokinins. The cytokinin ribosides were generally less active than the free bases. Abscisic acid and xanthoxin inhibited both emergence and elongation, the concentration for 50% decrease of emergence being about 10-4M. Gibberellic acid had little clear effect on any of the three criteria. Nicotinic acid and thiamine at 10-3M promoted both the initiation of primordia and their emergence: pyridoxal phosphate stimulated both emergence and elongation but did not influence the initiation of primordia. Adenine and guanine had little effect but decreased root elongation some 25%. The strong inhibiting effect of the cytokinins may well be the basis for the marked inhibition exerted by the root-tip on lateral root formation, while the promoting effects of auxins may explain the previously observed promotion of lateral root formation by the young shoot and cotyledons."