Natural plant hormones cytokinins increase stress resistance and longevity of Caenorhabditis elegans
Kadlecová, Alena ; Jirsa, Tomáš ; Novák, Ondřej ; Kammenga, Jan ; Strnad, Miroslav ; Voller, Jiří - \ 2018
Biogerontology 19 (2018)2. - ISSN 1389-5729 - p. 109 - 120.
Aging - Caenorhabditis elegans - Cytokinin - Kinetin - Phytohormones - Topolin - Zeatin
Cytokinins are phytohormones that are involved in many processes in plants, including growth, differentiation and leaf senescence. However, they also have various activities in animals. For example, kinetin and trans-zeatin can reduce levels of several aging markers in human fibroblasts. Kinetin can also protect mice against oxidative and glyoxidative stress, and prolong fruit flies’ lifespan. Additionally, several cytokinins are currently used in cosmetics. To extend knowledge of the breadth of cytokinins’ activities, we examined effects of natural cytokinin bases on the model nematode Caenorhabditis elegans. We found that kinetin, para-topolin and meta-topolin prolonged the lifespan of C. elegans. Kinetin also protected the organism against oxidative and heat stress. Furthermore, our results suggest that presence of reactive oxygen species, but not DAF-16 (the main effector of the insulin/insulin-like growth factor signaling pathway), is required for the beneficial effects of kinetin. Ultra-high performance liquid chromatography-tandem mass spectrometric analysis showed that kinetin is unlikely to occur naturally in C. elegans, but the worm efficiently absorbs and metabolizes it into kinetin riboside and kinetin riboside-5′-monophosphate.
Theoretical approaches to understanding root vascular patterning : A consensus between recent models
Mellor, Nathan ; Adibi, Milad ; El-Showk, Sedeer ; Rybel, Bert De; King, John ; Mähönen, Ari Pekka ; Weijers, Dolf ; Bishopp, Anthony ; Etchells, Peter - \ 2017
Journal of Experimental Botany 68 (2017)1. - ISSN 0022-0957 - p. 5 - 16.
Auxin - Cytokinin - Mathematical modeling - Organ patterning - Systems biology - Vascular development
The root vascular tissues provide an excellent system for studying organ patterning, as the specification of these tissues signals a transition from radial symmetry to bisymmetric patterns. The patterning process is controlled by the combined action of hormonal signaling/transport pathways, transcription factors, and miRNA that operate through a series of non-linear pathways to drive pattern formation collectively. With the discovery of multiple components and feedback loops controlling patterning, it has become increasingly difficult to understand how these interactions act in unison to determine pattern formation in multicellular tissues. Three independent mathematical models of root vascular patterning have been formulated in the last few years, providing an excellent example of how theoretical approaches can complement experimental studies to provide new insights into complex systems. In many aspects these models support each other; however, each study also provides its own novel findings and unique viewpoints. Here we reconcile these models by identifying the commonalities and exploring the differences between them by testing how transferable findings are between models. New simulations herein support the hypothesis that an asymmetry in auxin input can direct the formation of vascular pattern. We show that the xylem axis can act as a sole source of cytokinin and specify the correct pattern, but also that broader patterns of cytokinin production are also able to pattern the root. By comparing the three modeling approaches, we gain further insight into vascular patterning and identify several key areas for experimental investigation.
Auxin synthesis gene tms1 driven by tuber-specific promoter alters hormonal status of transgenic potato plants and their responses to exogenous phytohormones
Kolachevskaya, Oksana O. ; Sergeeva, Lidia ; Floková, Kristyna ; Getman, Irina A. ; Lomin, Sergey N. ; Alekseeva, Valeriya V. ; Rukavtsova, Elena B. ; Buryanov, Yaroslav I. ; Romanov, Georgy A. - \ 2017
Plant Cell Reports 36 (2017)3. - ISSN 0721-7714 - p. 419 - 435.
Auxin - Cytokinin - Hormonal status - Phytohormones - Potato - Solanum tuberosum - Transformants - Tuberization
Key message: Ectopic auxin overproduction in transgenic potato leads to enhanced productivity accompanied with concerted and occasional changes in hormonal status, and causing altered response of transformants to exogenous auxin or cytokinin.Abstract: Previously, we generated potato transformants expressing Agrobacterium-derived auxin synthesis gene tms1 driven by tuber-specific patatin gene promoter (B33-promoter). Here, we studied the endogenous hormonal status and the response to exogenous phytohormones in tms1 transformants cultured in vitro. Adding indole-3-acetic acid (IAA) or kinetin to culture medium affected differently tuberization of tms1-transformed and control plants, depending also on sucrose content in the medium. Exogenous phytohormones ceased to stimulate the tuber initiation in transformants at high (5–8%) sucrose concentration, while in control plants the stimulation was observed in all experimental settings. Furthermore, exogenous auxin partly inhibited the tuber initiation, and exogenous cytokinin reduced the average tuber weight in most transformants at high sucrose content. The elevated auxin level in tubers of the transformants was accompanied with a decrease in content of cytokinin bases and their ribosides in tubers and most shoots. No concerted changes in contents of abscisic, jasmonic, salicylic acids and gibberellins in tubers were detected. The data on hormonal status indicated that the enhanced productivity of tms1 transformants was due to auxin and not mediated by other phytohormones. In addition, exogenous cytokinin was shown to upregulate the expression of genes encoding orthologs of auxin receptors. Overall, the results showed that tms1 expression and local increase in IAA level in transformants affect both the balance of endogenous cytokinins and the dynamics of tuberization in response to exogenous hormones (auxin, cytokinin), the latter reaction depending also on the carbohydrate supply. We introduce a basic model for the hormonal network controlling tuberization.
Members of a recently discovered subfamily of cytokinin receptors display differences and similarities to their classical counterparts
Gruhn, Nijuscha ; Seidl, M.F. ; Halawa, Mhyeddeen ; Heyl, Alexander - \ 2015
Plant Signaling & Behavior 10 (2015)2. - ISSN 1559-2316
Cytokinin - Cytokinin receptor - Evolution - Signal transduction - Two-component signaling
Cytokinins represent a group of plant hormones that have been shown to be essential for plant growth and development. A recent large-scale phylogenetic analysis of components of the cytokinin signal transduction pathway revealed, among other findings, the existence of a second, previously unknown subfamily of cytokinin receptors. Here we report that the cytokinin binding domains of the members of the 2 subfamilies contain residues that are highly conserved in either or in both subfamilies. Experiments using fluorescence microscopy hint at an ER and a plasma membrane localization for 2 members of the newly identified subfamily. These data provide new insights in the conservation of sequence and localization properties among the 2 subfamilies.