Beyond transport: cytokinin ribosides are translocated and active in regulating the development and environmental responses of plants

Nguyen, Hai Ngoc; Nguyen, Thien Q.; Kisiała, Anna; Emery, Robert J.

doi:10.1007/s00425-021-03693-2

Cited by 32 publications

(35 citation statements)

References 157 publications

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“…The absence of root elongation response correlated with the absence of the changes in zeatin riboside concentration in the roots of Az34. These results suggest that zeatin riboside may play a more important role than was previously suggested, which is in accordance with the recent review, showing that ribosides of cytokinins are not merely the transport form of these hormones but are active in regulating the development and environmental responses of plants [27].…”

Section: Discussionsupporting

confidence: 92%

“…It has been shown previously that inhibition secondary active transmembrane transport by application of protonophore CCCP results in a decline in cytokinin concentration in the roots, suggesting that its active uptake by roots prevented cytokinin export from roots to shoots [22]. Cytokinins up taken from apoplast are likely to originate either from root cells capable to synthesize them [11] or delivered from shoots through phloem [27,28]. Present research does not allow us to identify exact cytokinin transporters involved in the control of cytokinin accumulation in the roots under supra-optimal concentration of mineral nutrients.…”

Section: Discussionmentioning

confidence: 96%

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Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

Vysotskaya

Timergalina

Akhiyarova

et al. 2021

Cells

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Changes in root elongation are important for the acquisition of mineral nutrients by plants. Plant hormones, cytokinins, and abscisic acid (ABA) and their interaction are important for the control of root elongation under changes in the availability of ions. However, their role in growth responses to supra-optimal concentrations of nitrates and phosphates has not been sufficiently studied and was addressed in the present research. Effects of supra-optimal concentrations of these ions on root elongation and distribution of cytokinins between roots and shoots were studied in ABA-deficient barley mutant Az34 and its parental variety, Steptoe. Cytokinin concentration in the cells of the growing root tips was analyzed with the help of an immunohistochemical technique. Increased concentrations of nitrates and phosphates led to the accumulation of ABA and cytokinins in the root tips, accompanied by a decline in shoot cytokinin content and inhibition of root elongation in Steptoe. Neither of the effects were detected in Az34, suggesting the importance of the ability of plants to accumulate ABA for the control of these responses. Since cytokinins are known to inhibit root elongation, the effect of supra-optimal concentration of nitrates and phosphates on root growth is likely to be due to the accumulation of cytokinins brought about by ABA-induced inhibition of cytokinin transport from roots to shoots.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 96%

Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

Vysotskaya

Timergalina

Akhiyarova

et al. 2021

Cells

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“…They typically occur as a mixture in plants, including free bases (or nucleobases), their ribosides and ribotides, as well as O -, N 7- and N 9-linked sugar conjugates. Recently, a review appeared in Planta focusing on CK ribosides and describing their history, metabolism, transport and putative functions (Nguyen et al 2021 ). Importantly, the authors propose that the long-standing view that the active CKs are their free base forms should be expanded to include respective ribosides (Nguyen et al 2021 ).…”

Section: Introductionmentioning

confidence: 99%

“…Recently, a review appeared in Planta focusing on CK ribosides and describing their history, metabolism, transport and putative functions (Nguyen et al 2021 ). Importantly, the authors propose that the long-standing view that the active CKs are their free base forms should be expanded to include respective ribosides (Nguyen et al 2021 ). The main arguments put forward by the authors has been the correlation of high concentrations of CK ribosides with CK activities in planta and their apparent ability to bind to CK receptors in certain heterologous test systems mentioned further below.…”

Section: Introductionmentioning

confidence: 99%

On the biological activity of cytokinin free bases and their ribosides

Romanov

Schmülling

2021

Planta

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Main conclusion The free bases of cytokinins are the biologically active forms of the hormone while cytokinin ribosides become active only upon removal of the ribose residue. Abstract Cytokinins (CKs) belong to the classical plant hormones. They were discovered more than 65 years ago, but which molecular forms possess genuine CK activity is still matter of debate. Numerous studies support the view that only the free bases are the biologically active molecules. This standpoint has been challenged in a recent review (Nguyen et al. in Planta 254: 45, 2021) proposing that also CK ribosides may have genuine own CK activity. Here we critically discuss the pros and cons of this viewpoint considering the results of biological assays, CK binding studies, 3D structural data of CK-receptor interaction and mutant analyses. It is concluded that all types of study provide clear and convincing evidence only for biological activity of free bases and not ribosides; the latter are rather a transport form of the hormone without their own biological activity.

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“…Riboside (CK-RB) and nucleotide (CK-NT) forms are usually considered to be less biologically active, as CK-NTs are the stable precursors to more active CK forms (Sakakibara 2006;Romanov 2011), and CK-RBs are regarded as more suitable for transport within plants (Kudo et al 2010;Osugi et al 2017). On the other hand, Nguyen et al (2021) contest that CK-RBs have roles beyond transport, including potential direct activity (Nguyen et al 2021). In our study, both the CK-NTs and CK-RBs were less abundant than CK-FBs across the Methylobacterium analyzed.…”

Section: Discussionmentioning

confidence: 99%

A Survey of Methylobacterium Species and Strains Reveals Widespread Production and Varying Profiles of Cytokinin Phytohormones

Palberg¹,

Kisiała²,

Jorge³

et al. 2021

Preprint

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BackgroundSymbiotic Methylobacterium strains comprise a significant part of plant microbiomes. Their presence enhances plant productivity and stress resistance, prompting classification of these strains as plant growth-promoting bacteria (PGPB). Methylobacteria can synthesize unusually high levels of plant hormones, called cytokinins (CKs), including the most active form, trans-Zeatin (tZ). ResultsThis study provides a comprehensive inventory of 46 representatives of Methylobacterium genus with respect to phytohormone production in vitro, including 16 CK forms, abscisic acid (ABA) and indole-3-acetic acid (IAA). High performance-liquid chromatography - tandem mass spectrometry (HPLC-MS/MS) analyses revealed varying abilities of Methylobacterium strains to secrete phytohormones that ranged from 5.09 to 191.47 pmol mL-1 for total CKs, and 0.46 to 82.16 pmol mL-1 for tZ. Results indicate that reduced methanol availability, the sole carbon source for bacteria in the medium, stimulates CK secretion by Methylobacterium. Additionally, select strains were able to transform L-tryptophan into IAA while no ABA production was detected.ConclusionsTo better understand features of CKs in plants, this study uncovers CK profiles of Methylobacterium that are instrumental in microbe selection for effective biofertilizer formulations.

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Beyond transport: cytokinin ribosides are translocated and active in regulating the development and environmental responses of plants

Cited by 32 publications

References 157 publications

Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

On the biological activity of cytokinin free bases and their ribosides

A Survey of Methylobacterium Species and Strains Reveals Widespread Production and Varying Profiles of Cytokinin Phytohormones

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