Retargeting a maize β-glucosidase to the vacuole – Evidence from intact plants that zeatin-O-glucoside is stored in the vacuole

Kiran, Nagavalli Subbanna; Benková, Eva; Reková, Alena; Dubová, Jaroslava; Malbeck, Jiří; Palme, Klaus; Brzobohatý, Břetislav

doi:10.1016/j.phytochem.2012.03.012

Cited by 23 publications

(18 citation statements)

References 49 publications

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“…Taken together, there is currently no clear experimental evidence supporting the function of CKX proteins in the vacuole. However, we note that cytokinin has been detected in vacuoles (Fusseder and Ziegler, 1988;Kiran et al, 2012;Jiskrová et al, 2016), but its biological significance in this organelle remains obscure.…”

Section: Discussionmentioning

confidence: 88%

The Cytokinin Oxidase/Dehydrogenase CKX1 Is a Membrane-Bound Protein Requiring Homooligomerization in the Endoplasmic Reticulum for Its Cellular Activity

et al. 2018

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Degradation of the plant hormone cytokinin is controlled by cytokinin oxidase/dehydrogenase (CKX) enzymes. The molecular and cellular behavior of these proteins is still largely unknown. In this study, we show that CKX1 is a type II single-pass membrane protein that localizes predominantly to the endoplasmic reticulum (ER) in Arabidopsis (). This indicates that this CKX isoform is a bona fide ER protein directly controlling the cytokinin, which triggers the signaling from the ER. By using various approaches, we demonstrate that CKX1 forms homodimers and homooligomers in vivo. The amino-terminal part of CKX1 was necessary and sufficient for the protein oligomerization as well as for targeting and retention in the ER. Moreover, we show that protein-protein interaction is largely facilitated by transmembrane helices and depends on a functional GxxxG-like interaction motif. Importantly, mutations rendering CKX1 monomeric interfere with its steady-state localization in the ER and cause a loss of the CKX1 biological activity by increasing its ER-associated degradation. Therefore, our study provides evidence that oligomerization is a crucial parameter regulating CKX1 biological activity and the cytokinin concentration in the ER. The work also lends strong support for the cytokinin signaling from the ER and for the functional relevance of the cytokinin pool in this compartment.

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Section: Discussionmentioning

confidence: 88%

The Cytokinin Oxidase/Dehydrogenase CKX1 Is a Membrane-Bound Protein Requiring Homooligomerization in the Endoplasmic Reticulum for Its Cellular Activity

et al. 2018

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“…O-glycosylation is one of the first reactions to exogenous cytokinin application and produces non-active cytokinins that can be re-activated by β-glucosidases (Brzobohaty et al, 1993). Cytokinin O-glucosides could serve as a storage pool and readily available source of active free bases (Kiran et al, 2012). On the other hand, cytokinin glycosylation at the N7 and N9 positions of the adenine moiety catalysed by UGT76C1 and UGT76C2 enzymes (Hou et al, 2004;Wang et al, 2011) is irreversible, and therefore Nglucosides were proposed to represent a permanent deactivation in the cytokinin lifetime (Parker and Letham, 1973).…”

Section: Introductionmentioning

confidence: 99%

Cytokinin signalling regulates organ identity via the AHK4 receptor in Arabidopsis

et al. 2018

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Mutual interactions of the phytohormones, cytokinins and auxin determine root or shoot identity during postembryonic organogenesis in plants. However, our understanding of the role of hormonal metabolism and perception during early stages of cell fate reprogramming is still elusive. Here we show that auxin activates root formation, whereas cytokinins mediate early loss of the root identity, primordia disorganisation and initiation of shoot development. Exogenous and endogenous cytokinins influence the initiation of newly formed organs, as well as the pace of organ development. The process of shoot apical meristem establishment is accompanied by accumulation of endogenous cytokinins, differential regulation of genes for individual cytokinin receptors, strong activation of AHK4-mediated signalling and induction of the shoot-specific homeodomain regulator The last is associated with upregulation of isopentenyladenine-type cytokinins, revealing higher shoot-forming potential when compared with-zeatin. Moreover, AHK4-controlled cytokinin signalling negatively regulates the root stem cell organiser in the root quiescent centre. We propose an important role for endogenous cytokinin biosynthesis and AHK4-mediated cytokinin signalling in the control of-induced organ identity.

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“…The resulting plants had a CK status and phenotype that closely resembled those of the wild-type. This result indirectly suggests that the vacuole acts as a storage organelle for CK glycosides (Kiran et al 2012). Zm-p60.1 is clearly a powerful tool for manipulating endogenous CK levels in plants.…”

Section: Reactivationmentioning

confidence: 91%

“…This was accompanied by the inhibition of root elongation. In subsequent investigations, a vacuolar variant of Zm-p60.1 was generated and overexpressed in tobacco (Kiran et al 2012). As was the case for native Zm-p60.1 overexpressors, plants from this mutant line did not exhibit any phenotypic deviation under normal conditions.…”

Section: Reactivationmentioning

confidence: 98%

The Biotechnological Potential of Cytokinin Status Manipulation

Šmehilová

Spíchal

2013

Plant Cell Monographs

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Cytokinins are highly conserved plant hormones with a long evolutionary history that regulate various aspects of plant growth and development. The genetic background of the mechanisms involved in the regulation of plants' cytokinin status has recently been elucidated. Studies on transgenic plants with altered cytokinin biosynthesis, metabolism, degradation, or signaling revealed interesting consequences of cytokinin deficiency or disruption of cytokinin perception that can be applied in plant biotechnology and agriculture. Cytokinin levels and the sensing thereof can be manipulated using transgenic approaches and by treating plants with novel exogenous compounds in order to promote root system development, biomass formation, yield-forming traits, nutrient uptake, and tolerance of biotic and abiotic stresses. This chapter provides an overview of recent findings concerning the molecular basis and genetic background of cytokinin signaling and metabolism and the ways in which they can be manipulated to tailor plants' traits to meet specific requirements.

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Retargeting a maize β-glucosidase to the vacuole – Evidence from intact plants that zeatin-O-glucoside is stored in the vacuole

Cited by 23 publications

References 49 publications

The Cytokinin Oxidase/Dehydrogenase CKX1 Is a Membrane-Bound Protein Requiring Homooligomerization in the Endoplasmic Reticulum for Its Cellular Activity

The Cytokinin Oxidase/Dehydrogenase CKX1 Is a Membrane-Bound Protein Requiring Homooligomerization in the Endoplasmic Reticulum for Its Cellular Activity

Cytokinin signalling regulates organ identity via the AHK4 receptor in Arabidopsis

The Biotechnological Potential of Cytokinin Status Manipulation

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