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A plausible mechanism for auxin patterning along the developing root.

Mironova VV, Omelyanchuk NA, Yosiphon G, Fadeev SI, Kolchanov NA, Mjolsness E, Likhoshvai VA - BMC Syst Biol (2010)

Bottom Line: In addition, the proximal maxima are formed under the reflected flow mechanism in response to periods of increasing auxin flow from the growing shoot.These events may predetermine lateral root initiation in a rhyzotactic pattern.Another outcome of the reflected flow mechanism - the predominance of lateral or adventitious roots in different plant species - may be based on the different efficiencies with which auxin inhibits its own transport in different species, thereby distinguishing two main types of plant root architecture: taproot vs. fibrous.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Cytology and Genetics, SB RAS, Lavrentyeva 10, Novosibirsk, Russia.

ABSTRACT

Background: In plant roots, auxin is critical for patterning and morphogenesis. It regulates cell elongation and division, the development and maintenance of root apical meristems, and other processes. In Arabidopsis, auxin distribution along the central root axis has several maxima: in the root tip, in the basal meristem and at the shoot/root junction. The distal maximum in the root tip maintains the stem cell niche. Proximal maxima may trigger lateral or adventitious root initiation.

Results: We propose a reflected flow mechanism for the formation of the auxin maximum in the root apical meristem. The mechanism is based on auxin's known activation and inhibition of expressed PIN family auxin carriers at low and high auxin levels, respectively. Simulations showed that these regulatory interactions are sufficient for self-organization of the auxin distribution pattern along the central root axis under varying conditions. The mathematical model was extended with rules for discontinuous cell dynamics so that cell divisions were also governed by auxin, and by another morphogen Division Factor which combines the actions of cytokinin and ethylene on cell division in the root. The positional information specified by the gradients of these two morphogens is able to explain root patterning along the central root axis.

Conclusion: We present here a plausible mechanism for auxin patterning along the developing root, that may provide for self-organization of the distal auxin maximum when the reverse fountain has not yet been formed or has been disrupted. In addition, the proximal maxima are formed under the reflected flow mechanism in response to periods of increasing auxin flow from the growing shoot. These events may predetermine lateral root initiation in a rhyzotactic pattern. Another outcome of the reflected flow mechanism - the predominance of lateral or adventitious roots in different plant species - may be based on the different efficiencies with which auxin inhibits its own transport in different species, thereby distinguishing two main types of plant root architecture: taproot vs. fibrous.

Show MeSH
Representation in the model the processes influencing the auxin distribution along the central root axis. a. Acropetal flow is considered in the model along the cell array on the central root axis (x axis). Arrows denote the processes that provide for auxin movements considered in the model. b. The summarized mechanism providing for regulation of PIN1 expression comprises the regulation of PIN1 protein synthesis and degradation depending on the auxin concentration.
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Figure 1: Representation in the model the processes influencing the auxin distribution along the central root axis. a. Acropetal flow is considered in the model along the cell array on the central root axis (x axis). Arrows denote the processes that provide for auxin movements considered in the model. b. The summarized mechanism providing for regulation of PIN1 expression comprises the regulation of PIN1 protein synthesis and degradation depending on the auxin concentration.

Mentions: PIN1 concentration dynamics in individual cell was defined by auxin-dependent rates of PIN1 synthesis and degradation (Figure 1B). The rate of PIN1 protein syntheses was approximated by the following Hill function:(5)


A plausible mechanism for auxin patterning along the developing root.

Mironova VV, Omelyanchuk NA, Yosiphon G, Fadeev SI, Kolchanov NA, Mjolsness E, Likhoshvai VA - BMC Syst Biol (2010)

Representation in the model the processes influencing the auxin distribution along the central root axis. a. Acropetal flow is considered in the model along the cell array on the central root axis (x axis). Arrows denote the processes that provide for auxin movements considered in the model. b. The summarized mechanism providing for regulation of PIN1 expression comprises the regulation of PIN1 protein synthesis and degradation depending on the auxin concentration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2921385&req=5

Figure 1: Representation in the model the processes influencing the auxin distribution along the central root axis. a. Acropetal flow is considered in the model along the cell array on the central root axis (x axis). Arrows denote the processes that provide for auxin movements considered in the model. b. The summarized mechanism providing for regulation of PIN1 expression comprises the regulation of PIN1 protein synthesis and degradation depending on the auxin concentration.
Mentions: PIN1 concentration dynamics in individual cell was defined by auxin-dependent rates of PIN1 synthesis and degradation (Figure 1B). The rate of PIN1 protein syntheses was approximated by the following Hill function:(5)

Bottom Line: In addition, the proximal maxima are formed under the reflected flow mechanism in response to periods of increasing auxin flow from the growing shoot.These events may predetermine lateral root initiation in a rhyzotactic pattern.Another outcome of the reflected flow mechanism - the predominance of lateral or adventitious roots in different plant species - may be based on the different efficiencies with which auxin inhibits its own transport in different species, thereby distinguishing two main types of plant root architecture: taproot vs. fibrous.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Cytology and Genetics, SB RAS, Lavrentyeva 10, Novosibirsk, Russia.

ABSTRACT

Background: In plant roots, auxin is critical for patterning and morphogenesis. It regulates cell elongation and division, the development and maintenance of root apical meristems, and other processes. In Arabidopsis, auxin distribution along the central root axis has several maxima: in the root tip, in the basal meristem and at the shoot/root junction. The distal maximum in the root tip maintains the stem cell niche. Proximal maxima may trigger lateral or adventitious root initiation.

Results: We propose a reflected flow mechanism for the formation of the auxin maximum in the root apical meristem. The mechanism is based on auxin's known activation and inhibition of expressed PIN family auxin carriers at low and high auxin levels, respectively. Simulations showed that these regulatory interactions are sufficient for self-organization of the auxin distribution pattern along the central root axis under varying conditions. The mathematical model was extended with rules for discontinuous cell dynamics so that cell divisions were also governed by auxin, and by another morphogen Division Factor which combines the actions of cytokinin and ethylene on cell division in the root. The positional information specified by the gradients of these two morphogens is able to explain root patterning along the central root axis.

Conclusion: We present here a plausible mechanism for auxin patterning along the developing root, that may provide for self-organization of the distal auxin maximum when the reverse fountain has not yet been formed or has been disrupted. In addition, the proximal maxima are formed under the reflected flow mechanism in response to periods of increasing auxin flow from the growing shoot. These events may predetermine lateral root initiation in a rhyzotactic pattern. Another outcome of the reflected flow mechanism - the predominance of lateral or adventitious roots in different plant species - may be based on the different efficiencies with which auxin inhibits its own transport in different species, thereby distinguishing two main types of plant root architecture: taproot vs. fibrous.

Show MeSH