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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.


Expression of TCSn:GFP during LR development. Activity of cytokinin as visualized by TCSn:GFP is high in PCs on either side of LRP in wild-type plants. TCSn:GFP expression is reduced in PCs adjacent to LRP of the cytokinin-deficient ipt3 5 7 mutant. White asterisks indicate borders of LRP or emerged LRs. Scale bar is 100 µM (this figure is available in colour at JXB online).
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Figure 4: Expression of TCSn:GFP during LR development. Activity of cytokinin as visualized by TCSn:GFP is high in PCs on either side of LRP in wild-type plants. TCSn:GFP expression is reduced in PCs adjacent to LRP of the cytokinin-deficient ipt3 5 7 mutant. White asterisks indicate borders of LRP or emerged LRs. Scale bar is 100 µM (this figure is available in colour at JXB online).

Mentions: The LRP spacing defect phenotype was further analysed by counting the PC number between two closely positioned LRP in ipt3 5 7 and log4 roots compared to wild type. Fig. 3B shows that both cytokinin-synthesis mutants had a higher proportion of LRP separated by zero to three PCs (44.5% for ipt3 5 7 and 47.9% for log4) as compared to wild type (22.8%). The largest difference in LRP specification between the cytokinin-synthesis mutants and the wild type was immediately adjacent to an already initiated LR and then declined gradually, showing an almost similar frequency at a distance of three PCs (Fig. 3B). This gradient of activity could possibly be due to a cytokinin flow originating in young LRP and caused by the combined activities of IPT5 and LOG4 that primarily affect the immediately adjacent cells (Fig. 2A). Fig. 4 shows that reduced cytokinin synthesis in and around LRP affects the cytokinin output signal in the zone of high cytokinin sensitivity surrounding LRP (Bielach et al., 2012). The signal of the cytokinin reporter TCSn:GFP (Zürcher et al., 2013) in wild type was high in cells neighbouring LRP but lower in these cells in roots of the cytokinin-synthesis mutant ipt3 5 7. This is consistent with a lower inhibitory activity of cytokinin on LR initiation in these cells.


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

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

Expression of TCSn:GFP during LR development. Activity of cytokinin as visualized by TCSn:GFP is high in PCs on either side of LRP in wild-type plants. TCSn:GFP expression is reduced in PCs adjacent to LRP of the cytokinin-deficient ipt3 5 7 mutant. White asterisks indicate borders of LRP or emerged LRs. Scale bar is 100 µM (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 4: Expression of TCSn:GFP during LR development. Activity of cytokinin as visualized by TCSn:GFP is high in PCs on either side of LRP in wild-type plants. TCSn:GFP expression is reduced in PCs adjacent to LRP of the cytokinin-deficient ipt3 5 7 mutant. White asterisks indicate borders of LRP or emerged LRs. Scale bar is 100 µM (this figure is available in colour at JXB online).
Mentions: The LRP spacing defect phenotype was further analysed by counting the PC number between two closely positioned LRP in ipt3 5 7 and log4 roots compared to wild type. Fig. 3B shows that both cytokinin-synthesis mutants had a higher proportion of LRP separated by zero to three PCs (44.5% for ipt3 5 7 and 47.9% for log4) as compared to wild type (22.8%). The largest difference in LRP specification between the cytokinin-synthesis mutants and the wild type was immediately adjacent to an already initiated LR and then declined gradually, showing an almost similar frequency at a distance of three PCs (Fig. 3B). This gradient of activity could possibly be due to a cytokinin flow originating in young LRP and caused by the combined activities of IPT5 and LOG4 that primarily affect the immediately adjacent cells (Fig. 2A). Fig. 4 shows that reduced cytokinin synthesis in and around LRP affects the cytokinin output signal in the zone of high cytokinin sensitivity surrounding LRP (Bielach et al., 2012). The signal of the cytokinin reporter TCSn:GFP (Zürcher et al., 2013) in wild type was high in cells neighbouring LRP but lower in these cells in roots of the cytokinin-synthesis mutant ipt3 5 7. This is consistent with a lower inhibitory activity of cytokinin on LR initiation in these cells.

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.