The Origins and Roles of Methylthiolated Cytokinins: Evidence From Among Life Kingdoms

Gibb, Maya; Kisiała, Anna; Morrison, Erin N.; Emery, Robert J.

doi:10.3389/fcell.2020.605672

Cited by 27 publications

(14 citation statements)

References 92 publications

(194 reference statements)

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“…While the levels of CK methylthioderivatives increased progressively during ontogeny of N. tabacum with a maximum at stage 6, they peaked (analogous to classical CKs) at stage 4 in N. alata, N. langsdorffii, and N. mutabilis. This suggests increasing tRNA turnover at stage 4 in the latter three species, as methylthiol-type CKs are known to arise exclusively via the tRNA degradation pathway (Tarkowski et al, 2010;Gibb et al, 2020). It also agrees well with the findings of Tupý (1982) that during pollen maturation, gene expression activity decreases, mRNA dissociates from ribosomes, and the uptake capacity of pollen grains further increases, indicating active utilization of metabolites released from the degenerating tapetal cytoplasm.…”

Section: Discussionsupporting

confidence: 88%

Hormonome Dynamics During Microgametogenesis in Different Nicotiana Species

et al. 2021

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Plant microgametogenesis involves stages leading to the progressive development of unicellular microspores into mature pollen. Despite the active and continuing interest in the study of male reproductive development, little is still known about the hormonomics at each ontogenetic stage. In this work, we characterized the profiles and dynamics of phytohormones during the process of microgametogenesis in four Nicotiana species (Nicotiana tabacum, Nicotiana alata, Nicotiana langsdorffii, and Nicotiana mutabilis). Taking advantage of advanced HPLC-ESI-MS/MS, twenty to thirty endogenous hormone derivatives were identified throughout pollen ontogenesis, including cytokinins, auxins, ABA and its derivatives, jasmonates, and phenolic compounds. The spectra of endogenous phytohormones changed dynamically during tobacco pollen ontogeny, indicating their important role in pollen growth and development. The different dynamics in the accumulation of endogenous phytohormones during pollen ontogenesis between N. tabacum (section Nicotiana) and the other three species (section Alatae) reflects their different phylogenetic positions and origin within the genus Nicotiana. We demonstrated the involvement of certain phytohormone forms, such as cis-zeatin- and methylthiol-type CKs, some derivatives of abscisic acid, phenylacetic and benzoic acids, in pollen development for the first time here. Our results suggest that unequal levels of endogenous hormones and the presence of specific derivatives may be characteristic for pollen development in different phylogenetic plant groups. These results represent the currently most comprehensive study of plant hormones during the process of pollen development.

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Section: Discussionsupporting

confidence: 88%

Hormonome Dynamics During Microgametogenesis in Different Nicotiana Species

et al. 2021

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“…The first step leading to the synthesis of CK derivatives in tRNA is the isopentenylation of the exocyclic amine of A37 in tRNAs with adenosine in the third anticodon position (position 36) by tRNA IPT, resulting in the formation of iPR [ 8 ]. This is followed by methylthiolation, and/or, in some organisms, by cis -hydroxylation (for review, see [ 51 ]). The miaA genes encoding tRNA IPT are present in all bacterial species, with the exception of the genus Mycoplasma [ 39 ].…”

Section: The Initial Step Of Ck Biosynthesis: Two Different Pathwaysmentioning

confidence: 99%

“…The simplest explanation for tZ presence would be a direct transfer of hydroxylated side-chain to A37 in tRNA by tRNA IPT, such as observed in Nostoc [ 20 ]. It is generally accepted that tRNA 2MeSiPR monooxygenase (MiaE), the only enzyme known to hydroxylate tRNA-bound iP, synthesizes 2MeScZRMP and cZRMP [ 10 , 51 , 61 ]. Yet, trans -selective hydroxylation of tRNA-bound iPR or 2MeSiPR by the same enzyme was reported by others [ 62 , 63 ].…”

Section: Formation Of Trans -Zeatin: Unclarified Pmentioning

confidence: 99%

Biochemical and Structural Aspects of Cytokinin Biosynthesis and Degradation in Bacteria

Frébortová

Frébort

2021

Microorganisms

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It has been known for quite some time that cytokinins, hormones typical of plants, are also produced and metabolized in bacteria. Most bacteria can only form the tRNA-bound cytokinins, but there are examples of plant-associated bacteria, both pathogenic and beneficial, that actively synthesize cytokinins to interact with their host. Similar to plants, bacteria produce diverse cytokinin metabolites, employing corresponding metabolic pathways. The identification of genes encoding the enzymes involved in cytokinin biosynthesis and metabolism facilitated their detailed characterization based on both classical enzyme assays and structural approaches. This review summarizes the present knowledge on key enzymes involved in cytokinin biosynthesis, modifications, and degradation in bacteria, and discusses their catalytic properties in relation to the presence of specific amino acid residues and protein structure.

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“…Some other naturally occurring CKs are synthesized not by plants themselves, but rather by plant pathogens. These include various methylated, thiomethylated, and deoxyribosylated variants of iP and zeatin-type CKs [ 49 , 50 , 51 , 52 ]. These compounds have been shown to mimic physiological CK activity, effectively disrupting the hormonal balance in host plants and facilitating the infection.…”

Section: The Structural Variety Of Naturally Occurring and Synthetmentioning

confidence: 99%

Differential Subcellular Distribution of Cytokinins: How Does Membrane Transport Fit into the Big Picture?

Nedvěd

Hošek

Klíma

et al. 2021

IJMS

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Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of “equilibrative nucleoside transporters” and “purine permeases”, which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness.

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The Origins and Roles of Methylthiolated Cytokinins: Evidence From Among Life Kingdoms

Cited by 27 publications

References 92 publications

Hormonome Dynamics During Microgametogenesis in Different Nicotiana Species

Hormonome Dynamics During Microgametogenesis in Different Nicotiana Species

Biochemical and Structural Aspects of Cytokinin Biosynthesis and Degradation in Bacteria

Differential Subcellular Distribution of Cytokinins: How Does Membrane Transport Fit into the Big Picture?

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