The trans and cis zeatin isomers play different roles in regulating growth inhibition induced by high nitrate concentrations in maize
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Abscisic acid (ABA), auxins, and cytokinins (CKs) are known to be closely linked to nitrogen signaling. In particular, CKs control the effects of nitrate availability on plant growth. Our group has shown that treatment with high nitrate concentrations limits root growth and leaf development in maize, and conditions the development of younger roots and leaves. CKs also affect source-sink relationships in plants. Based on these results, we hypothesized that CKs regulate the source-sink relationship in maize via a mechanism involving complex crosstalk with the main auxin indole-3-acetic acid (IAA) and ABA. To evaluate this hypothesis, various CK metabolites, IAA, and ABA were quantified in the roots and in source and sink leaves of maize plants treated with high and normal nitrate concentrations. The data obtained suggest that the cis and trans isomers of zeatin play completely distinct roles in maize growth regulation by a complex crosstalk with IAA and ABA. We demonstrate that while trans-zeatin (tZ) and isopentenyladenine (iP) regulate nitrate uptake and thus control final leaf sizes, cis-zeatin (cZ) regulates source and sink strength, and thus controls leaf development. The implications of these findings relating to the roles of ABA and IAA in plants’ responses to varying nitrate concentrations are also discussed.
KeywordsCytokinins IAA ABA Growth Fluorescence Nitrate Sink Source
The present authors would like to thank the company “sees-editing” for the English correction.
This work was partially supported by MEC-INIA (Grant RTA2010-00041-CO2-02) and GRUPO Gobierno-Vasco-IT1022-16, by the Ministry of Education, Youth and Sports of the Czech Republic (Grant LO1204 from the National Program of Sustainability) and the institutional funds of Palacky University.
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