pubmed.ncbi.nlm.nih.gov

Auxin/Cytokinin Antagonistic Control of the Shoot/Root Growth Ratio and Its Relevance for Adaptation to Drought and Nutrient Deficiency Stresses - PubMed

️Sat Jan 01 2022

Review

Auxin/Cytokinin Antagonistic Control of the Shoot/Root Growth Ratio and Its Relevance for Adaptation to Drought and Nutrient Deficiency Stresses

Jasmina Kurepa et al. Int J Mol Sci. 2022.

Abstract

The hormones auxin and cytokinin regulate numerous aspects of plant development and often act as an antagonistic hormone pair. One of the more striking examples of the auxin/cytokinin antagonism involves regulation of the shoot/root growth ratio in which cytokinin promotes shoot and inhibits root growth, whereas auxin does the opposite. Control of the shoot/root growth ratio is essential for the survival of terrestrial plants because it allows growth adaptations to water and mineral nutrient availability in the soil. Because a decrease in shoot growth combined with an increase in root growth leads to survival under drought stress and nutrient limiting conditions, it was not surprising to find that auxin promotes, while cytokinin reduces, drought stress tolerance and nutrient uptake. Recent data show that drought stress and nutrient availability also alter the cytokinin and auxin signaling and biosynthesis pathways and that this stress-induced regulation affects cytokinin and auxin in the opposite manner. These antagonistic effects of cytokinin and auxin suggested that each hormone directly and negatively regulates biosynthesis or signaling of the other. However, a growing body of evidence supports unidirectional regulation, with auxin emerging as the primary regulatory component. This master regulatory role of auxin may not come as a surprise when viewed from an evolutionary perspective.

Keywords: auxin signaling; auxin/cytokinin signaling crosstalk; cytokinin signaling; drought stress; hormone antagonism; nutrient deficiency; shoot/root growth ratio.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

**Figure 1**
Simplified schemes of the auxin and cytokinin response pathways. Abbreviations: AUX/IAAs, auxin/indole-3-acetic acid regulators; ARFs, auxin response factors; CHKs, cytokinin histidine kinase receptors; HPTs, histidine phosphotransfer proteins; RRBs, type-B response regulators; RRAs, type-A response regulators.

**Figure 2**
Increased shoot/root growth ratio in Arabidopsis auxin resistant mutants. Nineteen-day-old Col-0 wild type, *axr5-1*, *axr2-1*, and *axr3-3* plants, grown on vertical plates containing half-strength Murashige and Skoog medium, were dissected, and the fresh weights of shoots and roots were measured. Data are presented as mean ± SD (n ≥ 12 pools of 8 plants each). The significance of the difference between the wild type and the mutants is noted (****, p < 0.0001; two-way ANOVA with Bonferroni’s multiple comparisons test) *Kurepa et al., unpublished*.

**Figure 3**
Effects of nutrient or water availability and effects of the auxin/cytokinin ratio on the shoot/root growth ratio.

**Figure 4**
Schematic summary of the antagonistic cytokinin/auxin control of the shoot/root ratio in relation to water deficit and nutrient deficiency.

Cited by

Phytochemical and morpho-physiological response of Melissa officinalis L. to different NH₄⁺ to NO₃̄ ratios under hydroponic cultivation.
Safaei F, Alirezalu A, Noruzi P, Alirezalu K. Safaei F, et al. BMC Plant Biol. 2024 Oct 16;24(1):968. doi: 10.1186/s12870-024-05693-2. BMC Plant Biol. 2024. PMID: 39407126 Free PMC article.
Optimization of Plant Growth Regulators for In Vitro Mass Propagation of a Disease-Free 'Shine Muscat' Grapevine Cultivar.
Kim SH, Zebro M, Jang DC, Sim JE, Park HK, Kim KY, Bae HM, Tilahun S, Park SM. Kim SH, et al. Curr Issues Mol Biol. 2023 Sep 22;45(10):7721-7733. doi: 10.3390/cimb45100487. Curr Issues Mol Biol. 2023. PMID: 37886931 Free PMC article.
Effects of Aerated Drip Irrigation on the Soil Nitrogen Distribution, Crop Growth, and Yield of Chili Peppers.
Lei H, Xia J, Xiao Z, Chen Y, Jin C, Pan H, Pang Z. Lei H, et al. Plants (Basel). 2024 Feb 26;13(5):642. doi: 10.3390/plants13050642. Plants (Basel). 2024. PMID: 38475488 Free PMC article.
Soil Fertility Clock-Crop Rotation as a Paradigm in Nitrogen Fertilizer Productivity Control.
Grzebisz W, Diatta J, Barłóg P, Biber M, Potarzycki J, Łukowiak R, Przygocka-Cyna K, Szczepaniak W. Grzebisz W, et al. Plants (Basel). 2022 Oct 25;11(21):2841. doi: 10.3390/plants11212841. Plants (Basel). 2022. PMID: 36365294 Free PMC article. Review.
The Receptor Kinases DRUS1 and DRUS2 Behave Distinctly in Osmotic Stress Tolerance by Modulating the Root System Architecture via Auxin Signaling.
Latif A, Yang CG, Zhang LX, Yang XY, Liu XY, Ai LF, Noman A, Pu CX, Sun Y. Latif A, et al. Plants (Basel). 2024 Mar 16;13(6):860. doi: 10.3390/plants13060860. Plants (Basel). 2024. PMID: 38592851 Free PMC article.

References

1. Lynch J., Marschner P., Rengel Z. Effect of Internal and External Factors on Root Growth and Development. In: Marschner P., editor. Marschner’s Mineral Nutrition of Higher Plants. 3rd ed. Elsevier; Amsterdam, The Netherlands: 2012. pp. 331–346.
1. Greenwood D.J. Quantitative theory and the control of soil fertility. New Phytol. 1983;94:1–18. doi: 10.1111/j.1469-8137.1983.tb02715.x. - DOI
1. Gregory P., Shepherd K., Cooper P. Effects of fertilizer on root growth and water use of barley in N. Syria. J. Agric. Res. 1984;103:429–438. doi: 10.1017/S0021859600047407. - DOI
1. Chapin F.S., III . Ecological Aspects of Plant Mineral Nutrition. In: Tinker B., Laäuchli A., editors. Advances in Plant Nutrition. Vol. 3. Praeger Publishers; New York, NY, USA: 1988. pp. 161–191.
1. Kang J.G., Van Iersel M.W. Nutrient solution concentration affects shoot: Root ratio, leaf area ratio, and growth of subirrigated salvia (Salvia splendens) HortScience. 2004;39:49–54. doi: 10.21273/HORTSCI.39.1.49. - DOI

Auxin/Cytokinin Antagonistic Control of the Shoot/Root Growth Ratio and Its Relevance for Adaptation to Drought and Nutrient Deficiency Stresses - PubMed