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Antagonistic activity of auxin and cytokinin in shoot and root organs.

ABSTRACT: The hormones auxin and cytokinin are essential for plant growth and development. Because of the central importance of root and shoot apical meristems in plant growth, auxin/cytokinin interactions have been predominantly analyzed in relation to apical meristem formation and function. In contrast, the auxin/cytokinin interactions during organ growth have remained largely unexplored. Here, we show that a specific interaction between auxin and cytokinin operates in both the root and the shoot where it serves as an additional determinant of plant development. We found that auxin at low concentrations limits the action of cytokinin. An increase in cytokinin level counteracts this inhibitory effect and leads to an inhibition of auxin signaling. At higher concentrations of both hormones, these antagonistic interactions between cytokinin and auxin are absent. Thus, our results reveal a bidirectional and asymmetrical interaction of auxin and cytokinin beyond the bounds of apical meristems. The relation is bidirectional in that both hormones exert inhibitory effects on each other's signaling mechanisms. However, this relation is also asymmetrical because under controlled growth conditions, auxin present in nontreated plants suppresses cytokinin signaling, whereas the reverse is not the case.

SUBMITTER: Kurepa J

PROVIDER: S-EPMC6508789 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Antagonistic activity of auxin and cytokinin in shoot and root organs.

Kurepa Jasmina J Shull Timothy E TE Smalle Jan A JA

Plant direct 20190225 2

The hormones auxin and cytokinin are essential for plant growth and development. Because of the central importance of root and shoot apical meristems in plant growth, auxin/cytokinin interactions have been predominantly analyzed in relation to apical meristem formation and function. In contrast, the auxin/cytokinin interactions during organ growth have remained largely unexplored. Here, we show that a specific interaction between auxin and cytokinin operates in both the root and the shoot where ...[more]

PMID: 31245764

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Project description:Cremastra appendiculata has become endangered due to reproductive difficulties. Specifically, vegetative reproduction is almost its only way to reproduce, and, under natural conditions, it cannot grow branches, resulting in an extremely low reproductive coefficient (reproductive percentage). Here, we performed RNA-Seq and a differentially expressed gene (DEG) analysis of the three stages of lateral bud development in C. appendiculata after decapitation-dormancy (D2), transition (TD2), and emergence (TG2)-and the annual axillary bud natural break (G1) to gain insight into the molecular regulatory network of shoot branching in this plant. Additionally, we applied the auxin transport inhibitors N-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodibenzoic acid (TIBA) to a treated pseudobulb string of C. appendiculata to verify the conclusions obtained by the transcriptome. RNA-Seq provided a wealth of valuable information. Successive pairwise comparative transcriptome analyses revealed 5988 genes as DEGs. GO (Gene Ontology) and KEGG (Kyoto encyclopedia of genes and genomes) analyses of DEGs showed significant enrichments in phytohormone biosynthesis and metabolism, regulation of hormone levels, and a hormone-mediated signaling pathway. qRT-PCR validation showed a highly significant correlation (p < 0.01) with the RNA-Seq generated data. High-performance liquid chromatography (HPLC) and qRT-PCR results showed that, after decapitation, the NPA- and TIBA-induced lateral buds germinated due to rapidly decreasing auxin levels, caused by upregulation of the dioxygenase for auxin oxidation gene (DAO). Decreased auxin levels promoted the expression of isopentenyl transferase (IPT) and cytochrome P450 monooxygenase, family 735, subfamily A (CYP735A) genes and inhibited two carotenoid cleavage dioxygenases (CCD7 and CCD8). Zeatin levels significantly increased after the treatments. The increased cytokinin levels promoted the expression of WUSCHEL (WUS) and inhibited expression of BRANCHED1 (BRC1) in the cytokinin signal transduction pathway and initiated lateral bud outgrowth. Our data suggest that our theories concerning the regulation of shoot branching and apical dominance is really similar to those observed in annual plants. Auxin inhibits bud outgrowth and tends to inhibit cytokinin levels. The pseudobulb in the plant behaves in a similar manner to that of a shoot above the ground.

Dataset Information

Antagonistic activity of auxin and cytokinin in shoot and root organs.

Publications

Antagonistic activity of auxin and cytokinin in shoot and root organs.

Similar Datasets

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