Vacuolar and cytosolic cytokinin dehydrogenases of Arabidopsis thaliana: Heterologous expression, purification and properties

Kowalska, Marta; Galuszka, Petr; Frébortová, Jitka; Šebela, Marek; Béres, Tibor; Hluska, Tomáš; Šmehilová, Mária; Bilyeu, Kristin; Frébort, Ivo

doi:10.1016/j.phytochem.2010.08.013

Cited by 78 publications

(71 citation statements)

References 33 publications

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“…This is consistent with data indicating that increased cytokinin signaling in Ljsnf2 or through ectopic MtLog overexpression reduces nodulation (Tirichine et al, 2007;Mortier et al, 2014). Most Arabidopsis CKX have predicted signal peptides and are proposed to localize to the apoplast or vacuoles Kowalska et al, 2010). We also found LjCKX3 has a predicted secretion signal and is therefore likely degrading cytokinin in the extracellular space.…”

Section: Local Restriction Of Cytokinin Accumulation Is Required For supporting

confidence: 91%

CYTOKININ OXIDASE/DEHYDROGENASE3 Maintains Cytokinin Homeostasis during Root and Nodule Development in Lotus japonicus

et al. 2015

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Cytokinins are required for symbiotic nodule development in legumes, and cytokinin signaling responses occur locally in nodule primordia and in developing nodules. Here, we show that the Lotus japonicus Ckx3 cytokinin oxidase/dehydrogenase gene is induced by Nod factor during the early phase of nodule initiation. At the cellular level, pCkx3::YFP reporter-gene studies revealed that the Ckx3 promoter is active during the first cortical cell divisions of the nodule primordium and in growing nodules. Cytokinin measurements in ckx3 mutants confirmed that CKX3 activity negatively regulates root cytokinin levels. Particularly, tZ and DHZ type cytokinins in both inoculated and uninoculated roots were elevated in ckx3 mutants, suggesting that these are targets for degradation by the CKX3 cytokinin oxidase/dehydrogenase. The effect of CKX3 on the positive and negative roles of cytokinin in nodule development, infection and regulation was further clarified using ckx3 insertion mutants. Phenotypic analysis indicated that ckx3 mutants have reduced nodulation, infection thread formation and root growth. We also identify a role for cytokinin in regulating nodulation and nitrogen fixation in response to nitrate as ckx3 phenotypes are exaggerated at increased nitrate levels. Together, these findings show that cytokinin accumulation is tightly regulated during nodulation in order to balance the requirement for cell divisions with negative regulatory effects of cytokinin on infection events and root development.

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Section: Local Restriction Of Cytokinin Accumulation Is Required For supporting

confidence: 91%

CYTOKININ OXIDASE/DEHYDROGENASE3 Maintains Cytokinin Homeostasis during Root and Nodule Development in Lotus japonicus

et al. 2015

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“…Cytokinin levels are also regulated by cytokinin oxidases, copper-dependent amine oxidase enzymes that cleave the N 6 -side chains from tZ-and iP-type cytokinins, thus irreversibly inactivating them Werner et al, 2006). In most plant species, cytokinin oxidase is encoded by a multigene family whose members show distinct patterns of expression, intracellular locations, and enzymatic properties Kowalska et al, 2010). Several genes encoding cytokinin oxidases are induced rapidly upon cytokinin and auxin treatment in rice (Oryza sativa) and Arabidopsis (Tsai et al, 2012;Bhargava et al, 2013;Gao et al, 2014).…”

Section: Cytokininsmentioning

confidence: 99%

The Yin-Yang of Hormones: Cytokinin and Auxin Interactions in Plant Development

2015

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“…With the exception of N-3 glucosides, N-glucosides are generally not active in bioassays and it has been assumed that N-7 and N-9 glucosylation irreversibly inactivates CKs , whereas N-3 glucoside can be converted to the free base by b-glucosidases (Brzobohatý et al 1993). Recently, CK N-9 glucosides were found to be the preferred substrates of some CKX isoforms (Galuszka et al 2007;Kowalska et al 2010).…”

Section: Ck Metabolismmentioning

confidence: 99%

“…The substrate binds above the isoalloxazine plane of the FAD cofactor and its amino group forms a hydrogen bond with an aspartic acid-glutamic acid (Asp-Glu) pair that facilitates the oxidation (Malito et al 2004). Studies on the substrate specificity of Arabidopsis thaliana and maize CKX isoforms revealed that not only free bases and ribosides of isoprenoid CKs, including cis-zeatin (Šmehilová et al 2009;Pertry et al 2010;Gajdošová et al 2011), but also CK 9-glucosides and nucleotides are effectively cleaved by individual isoforms (Galuszka et al 2007;Kowalska et al 2010). It was also presented that aromatic CKs are degraded by CKX as well, although with lower reaction rates (Frébortová et al 2004;Galuszka et al 2007).…”

Section: Ck Metabolismmentioning

confidence: 99%

Cytokinins - recent news and views of evolutionally old molecules

Spíchal¹

2012

Functional Plant Biol.

156

169

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Cytokinins (CKs) are evolutionally old and highly conserved low-mass molecules that have been identified in almost all known organisms. In plants, they evolved into an important group of plant hormones controlling many physiological and developmental processes throughout the whole lifespan of the plant. CKs and their functions are, however, not unique to plants. In this review, the strategies and mechanisms of plants – and phylogenetically distinct plant-interacting organisms such as bacteria, fungi, nematodes and insects employing CKs or regulation of CK status in plants – are described and put into their evolutionary context. The major breakthroughs made in the last decade in the fields of CK biosynthesis, degradation and signalling are also summarised.

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Vacuolar and cytosolic cytokinin dehydrogenases of Arabidopsis thaliana: Heterologous expression, purification and properties

Cited by 78 publications

References 33 publications

CYTOKININ OXIDASE/DEHYDROGENASE3 Maintains Cytokinin Homeostasis during Root and Nodule Development in Lotus japonicus

CYTOKININ OXIDASE/DEHYDROGENASE3 Maintains Cytokinin Homeostasis during Root and Nodule Development in Lotus japonicus

The Yin-Yang of Hormones: Cytokinin and Auxin Interactions in Plant Development

Cytokinins - recent news and views of evolutionally old molecules

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