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Cytokinin as a positional cue regulating lateral root spacing in Arabidopsis.

Chang L, Ramireddy E, Schmülling T - J. Exp. Bot. (2015)

Bottom Line: Interestingly, mutation of CYP735A genes required for trans-zeatin biosynthesis caused strong defects in LR positioning, indicating an important role for this cytokinin metabolite in regulating LR spacing.Further it is shown that cytokinin and a known regulator of LR spacing, the receptor-like kinase ARABIDOPSIS CRINKLY4 (ACR4), operate in a non-hierarchical manner but might exert reciprocal control at the transcript level.Taken together, the results suggest that cytokinin acts as a paracrine hormonal signal in regulating root system architecture.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Albrecht-Thaer-Weg 6, D- 14195 Berlin, Germany Present address: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Science, Hubei University, Wuhan 430062, China.

No MeSH data available.


Related in: MedlinePlus

Model illustrating the action of cytokinin in regulating LR spacing. The model predicts that the suppression of LRI in PCs neighbouring existing LRFCs is a combined effect of cytokinin synthesized in LRFCs and cytokinin synthesized by neighbouring cells. Activity of IPT5 and LOG4 in LRFCs causes the formation of iP, which diffuses laterally. Neighbouring cells convert iP to tZ by CYP735A2 and, in addition, synthesize their own cytokinin to inhibit LR formation. LRFCs are characterized by a high auxin-to-cytokinin ratio, indicated by the orange colour, while adjacent PCs are characterized by a low auxin-to-cytokinin ratio, indicated in green (this figure is available in colour at JXB online).
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Figure 7: Model illustrating the action of cytokinin in regulating LR spacing. The model predicts that the suppression of LRI in PCs neighbouring existing LRFCs is a combined effect of cytokinin synthesized in LRFCs and cytokinin synthesized by neighbouring cells. Activity of IPT5 and LOG4 in LRFCs causes the formation of iP, which diffuses laterally. Neighbouring cells convert iP to tZ by CYP735A2 and, in addition, synthesize their own cytokinin to inhibit LR formation. LRFCs are characterized by a high auxin-to-cytokinin ratio, indicated by the orange colour, while adjacent PCs are characterized by a low auxin-to-cytokinin ratio, indicated in green (this figure is available in colour at JXB online).

Mentions: The positioning of LRP along the Arabidopsis main root defines a usually regular rhizotactic pattern and LRP do not form in close proximity to each other. The hormone cytokinin functions in suppressing the formation of LRP close to existing ones and thus acts as a positional cue regulating the distance between LRP. The positional signal is generated by locally and developmentally controlled precise tuning of cytokinin synthesis gene expression. The lower distance of LRP in cytokinin-synthesis mutants is hypothesized to be due to a local inhibitory cytokinin gradient originating from the LRFCs, and to cytokinin produced in PCs neighbouring LRFCs. This paracrine action of cytokinin, a combination of non-cell autonomous and cell autonomous activity, inhibits the formation of LRP in PCs neighbouring existing LRP. This hypothesis is supported by (i) the activation of cytokinin synthesis genes early during LRP development and their expression in neighbouring PCs; (ii) the fact that disruption of these genes causes aberrant positioning of LRP, with the strongest effect in the immediate vicinity of existing LRP; and (iii) a gradual decrease of the inhibitory cytokinin action in wild type with increasing distance from LRFCs. The proposed activity of cytokinin is summarized in a model (Fig. 7).


Cytokinin as a positional cue regulating lateral root spacing in Arabidopsis.

Chang L, Ramireddy E, Schmülling T - J. Exp. Bot. (2015)

Model illustrating the action of cytokinin in regulating LR spacing. The model predicts that the suppression of LRI in PCs neighbouring existing LRFCs is a combined effect of cytokinin synthesized in LRFCs and cytokinin synthesized by neighbouring cells. Activity of IPT5 and LOG4 in LRFCs causes the formation of iP, which diffuses laterally. Neighbouring cells convert iP to tZ by CYP735A2 and, in addition, synthesize their own cytokinin to inhibit LR formation. LRFCs are characterized by a high auxin-to-cytokinin ratio, indicated by the orange colour, while adjacent PCs are characterized by a low auxin-to-cytokinin ratio, indicated in green (this figure is available in colour at JXB online).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4507779&req=5

Figure 7: Model illustrating the action of cytokinin in regulating LR spacing. The model predicts that the suppression of LRI in PCs neighbouring existing LRFCs is a combined effect of cytokinin synthesized in LRFCs and cytokinin synthesized by neighbouring cells. Activity of IPT5 and LOG4 in LRFCs causes the formation of iP, which diffuses laterally. Neighbouring cells convert iP to tZ by CYP735A2 and, in addition, synthesize their own cytokinin to inhibit LR formation. LRFCs are characterized by a high auxin-to-cytokinin ratio, indicated by the orange colour, while adjacent PCs are characterized by a low auxin-to-cytokinin ratio, indicated in green (this figure is available in colour at JXB online).
Mentions: The positioning of LRP along the Arabidopsis main root defines a usually regular rhizotactic pattern and LRP do not form in close proximity to each other. The hormone cytokinin functions in suppressing the formation of LRP close to existing ones and thus acts as a positional cue regulating the distance between LRP. The positional signal is generated by locally and developmentally controlled precise tuning of cytokinin synthesis gene expression. The lower distance of LRP in cytokinin-synthesis mutants is hypothesized to be due to a local inhibitory cytokinin gradient originating from the LRFCs, and to cytokinin produced in PCs neighbouring LRFCs. This paracrine action of cytokinin, a combination of non-cell autonomous and cell autonomous activity, inhibits the formation of LRP in PCs neighbouring existing LRP. This hypothesis is supported by (i) the activation of cytokinin synthesis genes early during LRP development and their expression in neighbouring PCs; (ii) the fact that disruption of these genes causes aberrant positioning of LRP, with the strongest effect in the immediate vicinity of existing LRP; and (iii) a gradual decrease of the inhibitory cytokinin action in wild type with increasing distance from LRFCs. The proposed activity of cytokinin is summarized in a model (Fig. 7).

Bottom Line: Interestingly, mutation of CYP735A genes required for trans-zeatin biosynthesis caused strong defects in LR positioning, indicating an important role for this cytokinin metabolite in regulating LR spacing.Further it is shown that cytokinin and a known regulator of LR spacing, the receptor-like kinase ARABIDOPSIS CRINKLY4 (ACR4), operate in a non-hierarchical manner but might exert reciprocal control at the transcript level.Taken together, the results suggest that cytokinin acts as a paracrine hormonal signal in regulating root system architecture.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Albrecht-Thaer-Weg 6, D- 14195 Berlin, Germany Present address: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Science, Hubei University, Wuhan 430062, China.

No MeSH data available.


Related in: MedlinePlus