Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana : A factor of potential importance for auxin–cytokinin-regulated development

Abstract

One of the most long-lived models in plant science is the belief that the long-distance transport and ratio of two plant hormones, auxin and cytokinin, at the site of action control major developmental events such as apical dominance. We have used in vivo deuterium labeling and mass spectrometry to investigate the dynamics of homeostatic cross talk between the two plant hormones. Interestingly, auxin mediates a very rapid negative control of the cytokinin pool by mainly suppressing the biosynthesis via the isopentenyladenosine-5 -monophosphate-independent pathway. In contrast, the effect of cytokinin overproduction on the entire auxin pool in the plant was slower, indicating that this most likely is mediated through altered development. In addition, we were able to confirm that the lateral root meristems are likely to be the main sites of isopentenyladenosine-5 -monophosphate-dependent cytokinin synthesis, and that the aerial tissue of the plant surprisingly also was a significant source of cytokinin biosynthesis. Our demonstration of shoot-localized synthesis, together with data demonstrating that auxin imposes a very rapid regulation of cytokinin biosynthesis, illustrates that the two hormones can interact also on the metabolic level in controlling plant development, and that the aerial part of the plant has the capacity to synthesize its own cytokinin independent of long-range transport from the root system.

Strigolactone Acts Downstream of Auxin to Regulate Bud Outgrowth in Pea and Arabidopsis

“…It is likely that auxin response mutants have increased cytokinin content due to reduced auxin regulation of cytokinin biosynthesis (Nordströ m et al, 2004;Bennett et al, 2006). This may contribute to the additive branching phenotype of axr1 and SMS double mutant plants and, possibly in combination with impaired feedback signaling , to the poor response of axr1 shoots to grafting with wildtype rootstocks.…”

Shoot organogenesis, molecular analysis and secondary metabolite production of micropropagated Rehmannia glutinosa Libosch.

“…Auxin and cytokinin are known to exert a synergistic action on shoot regeneration from callus tissue in several plant species, for example Dorem ammoniacum (Irvani et al 2010). According to Nordström et al (2004) auxin can regulate cytokinin biosynthesis and reduce its level in plants. Therefore, a good balance between the two types of growth regulators is required.…”

Some fundamental aspects of modeling auxin patterning in the context of auxin-ethylene-cytokinin crosstalk

“…3,9 For example, auxin biosynthesis can be stimulated by ethylene and inhibited by cytokinins. [6][7][8]16 Based on the principle discussed above, a positive regulation of auxin concentration by ethylene can also be derived. Moreover, previous research also deduces that the POLARIS (PLS) gene 17,18 is also required for the correct regulation of auxin concentration.…”

“…3,[6][7][8][9] For example, experimental data show that exogenous application of cytokinin may reduce the endogenous auxin concentration. 6 It can therefore be considered that cytokinin has roles in the negative regulation of auxin biosynthesis, or positive regulation of auxin degradation or both. Moreover, experimental data also show that genes involved in auxin metabolism are differentially expressed in response to altered cytokinin levels and/or responsiveness in Arabidopsis.…”