AUXIN DISTRIBUTION IN A TRANSVERSE ROOT SECTION

Plants differ in the types of the root central cylinder: diarch, triarch, tetrarch, pentarch, or polyarch. The type of the symmetry is the reflection of the relative positions of xylem and phloem bundles in a cross section of the root. The mechanisms forming different types of symmetries in the central cylinder remain poorly understood. It is assumed that vasculature differentiation is triggered and controlled by plant hormone auxin (Sachs, 1969). We have developed a model that describes auxin flow through a cell layer, imitating a cross section of the vascular cylinder in a root. We have studied the stationary distributions of auxin in the cell layer depending on the model parameters. It is shown that the nonlinear processes of auxin transport regulation are responsible for the formation of asymmetric auxin distributions, which may be interpreted as the positional information for development of the diarch structure of the vascular cylinder. However, these distributions always coexist with uniform stationary distributions, not providing positional information. It is hypothesized that the most likely factor in the formation of the final auxin distribution in a root section is an appropriate geometry of the auxin flow from the shoot to the root.

1. Лихошвай В.А., Омельянчук Н.А., Миронова В.В. и др. Математическая модель распределения ауксина в корне растения // Онтогенез. 2007. Т. 38. С. 446–456.

2. Bauby H., Divol F., Truernit E. et al. Protophloem differentiation in early Arabidopsis thaliana development // Plant Cell Physiol. 2007. V. 48. P. 97–109.

3. Bayer E.M., Smith R.S., Mandel T. et al. Integration of transport-based models for phyllotaxis and midvein formation // Genes Dev. 2009. V. 23. P. 373–384.

4. Benková E., Ivanchenko M.G., Friml J. et al. A morphogenetic trigger: is there an emerging concept in plant developmental biology? // Trends Plant Sci. 2009. V. 14. P. 189–193.

5. Benková E., Michniewicz M., Sauer M. et al. Local, effl uxdependent auxin gradients as a common module for plant organ formation // Cell. 2003. V. 115. P. 591–602.

6. Bishopp A., Lehesranta S., Vatén A. et al. Phloem-transported cytokinin regulates polar auxin transport and maintains vascular pattern in the root meristem // Curr. Biol. 2011a. V. 21. P. 927–932.

7. Bishopp A., Help H., El-Showk S. et al. A mutually inhibitory interaction between auxin and cytokinin specifi es vascular pattern in roots // Curr. Biol. 2011b. V. 21. P. 917–926.

8. Capron A., Chatfi eld S., Provart N., Berleth T. Embryogenesis: pattern formation from a single cell // Arabidopsis Book. 2009. V. 7. P. e0126.

9. Help H., Mähönen A.P., Helariutta Y., Bishopp A. Bisymmetry in the embryonic root is dependent on cotyledon number and position // Plant Signal Behav. 2011. V. 6. P. 1837–1840.

10. Ibañes M., Fàbregas N., Chory J., Caño-Delgado A.I. Brassinosteroid signaling and auxin transport are required to establish the periodic pattern of Arabidopsis shoot vascular bundles // Proc. Natl. Acad. Sci. USA. 2009. V. 106. P. 13630–13635.

11. Ljung K., Hull A.K., Celenza J. et al. Sites and regulation of auxin biosynthesis in Arabidopsis roots // Plant Cell. 2005. V. 17. P. 1090–1104.

12. Mironova V.V., Omelyanchuk N.A., Novoselova E.S. et al. Combined in silico/in vivo analysis of mechanisms providing for root apical meristem self-organization and maintenance // Ann. Bot. 2012. V. 110. P. 349–360.

13. Mironova V.V., Omelyanchuk N.A., Yosiphon G. et al. A plausible mechanism for auxin patterning along the developing root // BMC Syst Biol. 2010. V. 98. Р. 98.

14. Mitchison G.J. A model for vein formation in higher plants // Proc. R. Soc. Lond. B. 1980. V. 207. P. 79–109.

15. Mitchison G.J., Hanke D.E., Sheldrake A.R. The polar transport of auxin and vein patterns in plants // Phil. Trans. R. Soc. Lond. B. 1981. V. 295. P. 461–471.

16. Muraro D., Wilson M., Bennett M.J. Root development: cytokinin transport matters, too! // Curr. Biol. 2011. V. 21. P. R423–425.

17. Muraro D., Mellor N., Pound M.P. et al. Integration of hormonal signaling networks and mobile microRNAs is required for vascular patterning in Arabidopsis roots // Proc. Natl Acad. Sci. USA. 2014. V. 111, P. 857–862.

18. Novoselova E.S., Mironova V.V., Omelyanchuk N.A. et al. Mathematical modeling of auxin transport in protoxylem and protophloem of Arabidopsis thaliana root tips // J. Bioinform. Comput. Biol. 2013. V. 11. 1340010.

19. Petrášek J., Friml J. Auxin transport routes in plant development // Development. 2009. V. 136. No. 16. P. 2675–2688.

20. Swarup R., Friml J., Marchant A. et al. Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex // Genes Dev. 2001. V. 15. P. 2648–2653.

21. Vieten A., Vanneste S., Wisniewska J. et al. Functional redundancy of PIN proteins is accompanied by auxin-dependent cross-regulation of PIN expression // Development. 2005. V. 132. P. 4521–4531.