Cytokinin effects on protein synthesis of in vitro systems of higher plants
About: This article is published in Plant and Cell Physiology.The article was published on 1976-02-01. It has received 29 citations till now. The article focuses on the topics: Cytokinin.
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TL;DR: Although indications are presented that the promotion of chloroplast development by cytokinins is closely connected with a stimulation of the gene expression program for plastogenesis, other sites of hormone action cannot be excluded and are discussed in the last part of the review.
139 citations
TL;DR: It is deduced that an iron-containing system plays an essential part in the initiation of the senescence process of Avena seedlings.
Abstract: The senescence of the first leaves of light-grown Avena seedlings when detached and placed in the dark is inhibited by α, α′-dipyridyl and α, α′, α″-tripyridyl at concentrations between 10−5 and 10−4 M. Five other chelating agents exert similar inhibiting effects at concentrations 3 to 30 times higher. The senescence of etiolated leaves, as shown by loss of carotenoid and protein, is similarly inhibited. Ethylene-diaminetetraacetate has a similar effect in the dark, though only at 10 mM and above, but in the light it causes bleaching of chlorophyll. It is deduced that an iron-containing system plays an essential part in the initiation of the senescence process.
93 citations
01 Jan 1980
TL;DR: Exogenous application of hormones is one of the most common methods in research into the mode of action of such substances, but it is rarely easy and often impossible to achieve with plant material because any given hormone may be produced in more than one location within the plant.
Abstract: Exogenous application of hormones is one of the most common methods in research into the mode of action of such substances. The rationale behind such approaches is based mainly on the idea of replacement of the endogenous, naturally occurring hormone by an exogenous hormone, the level of which may be controlled and its effect monitored. This is fairly easily accomplished in animal systems, where the gland synthesizing a particular hormone can be dissected out and the target tissue monitored after application of the exogenous hormone via the blood stream. This is rarely easy and often impossible to achieve with plant material because in most instances any given hormone may be produced in more than one location within the plant. Furthermore, the same organ or cell which produces the hormone may also be the target.
41 citations
TL;DR: It is shown that cytokinin-induced polyribosome formation is the result of an effect of the hormone on protein synthesis at the translational level, and it is proposed that certain genes are transcribed but their messengers are not translated.
Abstract: The group of naturally occurring plant hormones known as the cytokinins are defined by their ability to stimulate cell division in mature, differentiated, mitotically inactive cells in tissue culture. Evidence from the literature suggests that cytokinins play a specific role in regulating the progress of a plant cell through its division cycle;. the hormone appears to trigger the transition from G2 to mitosis. However the cytokinins are capable of evoking an array of physiological and developmental responses (many of which do not involve cell division) from different plant tissues and organs. One biochemical effect of the cytokinins is a dramatic and rapid stimulation of polyribosome formation in cultured soybean, cells which require these hormones for growth. Stationary-phase soybean cells, transferred to a medium containing a cytokinin, double in cell number within 36 hr, but when transferred to a medium of the same composition lacking a cytokinin, they do not grow., In vivo labeling with [35S] methionine and slab-gel electrophoresis demonstrated that cytokinin brings about qualitative changes in the spectrum of proteins synthesized by soybean cells which precede hormone-induced cell division. We have shown that cytokinin-induced polyribosome formation is the result of an effect of the hormone on protein synthesis at the translational level. We propose that, in the absence of the hormone, certain genes are transcribed but their messengers are not translated. These include mRNA's for specific cell division proteins. Cytokinins act as permissive factors, allowing cells to complete a genetically programmed sequence of events which was initiated by other factors.
28 citations
Cites background from "Cytokinin effects on protein synthe..."
...Third, numerous studies have shown that cytokinin can induce both qualitative and quantitative changes in protein synthesis (51-55)....
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TL;DR: By measuring the differences of the specific radioactivities of the polysomes the following results were revealed: 1) Kinetin increases the protein synthesis by an average of 35%-2) Auxin has no effect on protein synthesis.
Abstract: The influence of naphthalene-1-acetic acid and kinetin on protein synthesis in vivo was investigated by measuring the incorporation of radioactive amino acids into polypeptides of synthesizing polysomes. The second subculture of sterile pith tissue of Nicotiana tabacum L. cv. Wisconsin 38 grown on a medium containing only a minimum of growth substances was further starved in a small volume of medium lacking auxin and cytokinin for 12 h. An incubation period of 4 h with [14C]amino acids followed. The last 30 min of those incubations were carried out in the presence of actinomycin D and the last 20 min were performed under different conditions: a) without any growth substances, b) with naphthalene-l-acetic acid, c) with kinetin. By measuring the differences of the specific radioactivities of the polysomes the following results were revealed: 1) Kinetin increases the protein synthesis by an average of 35%-2) Auxin has no effect on protein synthesis.
25 citations