Hormone symphony during root growth and development

Abstract

Hormones regulate plant growth and development in response to external environmental stimuli via complex signal transduction pathways, which in turn form complex networks of interaction. Several classes of hormones have been reported, and their activity depends on their biosynthesis, transport, conjugation, accumulation in the vacuole, and degradation. However, the activity of a given hormone is also dependent on its interaction with other hormones. Indeed, there is a complex crosstalk between hormones that regulates their biosynthesis, transport, and/or signaling functionality, although some hormones have overlapping or opposite functions. The plant root is a particularly useful system in which to study the complex role of plant hormones in the plastic control of plant development. Physiological, cellular, and molecular genetic approaches have been used to study the role of plant hormones in root meristem homeostasis. In this review, we discuss recent findings on the synthesis, signaling, transport of hormones and role during root development and examine the role of hormone crosstalk in maintaining homeostasis in the apical root meristem.

Effects of externally supplied BSA on ZR, IAA, ABA, GA of plant Cinnamomum camphora cutting seedlings and root

“…The plant root is a particularly useful system in which to study the complex role of plant hormones in the plastic control of plant development [20] . It has been demonstrated that all the stages of adventitious root formation are dependent on, or regulated by endogenous or exogenous auxin [15] .…”

Some fundamental aspects of modeling auxin patterning in the context of auxin-ethylene-cytokinin crosstalk

“…3,[6][7][8][9] For example, experimental data show that exogenous application of cytokinin may reduce the endogenous auxin concentration. 6 It can therefore be considered that cytokinin has roles in the negative regulation of auxin biosynthesis, or positive regulation of auxin degradation or both.…”

“…3,9 For example, auxin biosynthesis can be stimulated by ethylene and inhibited by cytokinins. [6][7][8]16 Based on the principle discussed above, a positive regulation of auxin concentration by ethylene can also be derived.…”

“…1 Auxin concentration is regulated by diverse interacting hormones and their effects on gene expression. [2][3][4][5] This interaction means each cannot change independently of the various crosstalk components in space and time. Important questions for understanding hormonal crosstalk in root development include how hormone concentrations and expression of the associated regulatory and target genes are mutually related; and how patterning of both hormones and gene expression emerges under the action of hormonal crosstalk.…”

Modelling Plant Hormone Gradients

“…Experimental data on Arabidopsis root development, accumulated over many years, have shown that the complexity of the interactions between hormones and gene expression in the root is multi-faceted, with the following features. 1) the activities of hormones such as auxin, ethylene, cytokinin, abscisic acid, gibberellin and brassinosteroids depend on cellular context and exhibit either synergistic or antagonistic interactions (Garay-Arroyo et al, 2012); 2) cellular patterning in the Arabidopsis root is coordinated via a localized auxin concentration maximum in the root tip, requiring the regulated expression of specific genes (Sabatini et al, 1999); 3) auxin is directionally transported through plant tissues, providing positional and vectorial information during development (Vanneste and Friml, 2009;Adamowski and Friml, 2015); 4) auxin concentration and the associated regulatory and target genes are regulated by diverse interacting hormones and gene expression and therefore cannot change independently of the various crosstalk components in space and time (Garay-Arroyo et al, 2012); 5) other hormone concentrations, such as ethylene and cytokinin concentrations, and expression of the associated regulatory and target genes are also interlinked (e.g. To et al, 2004;Shi et al, 2012); and 6) transport of other hormones, such as cytokinin, from the shoot to the root in the phloem (Bishopp et al, 2011;Schaller et al, 2015) in combination with local biosynthesis, degradation and diffusion, could also be an important factor affecting the interaction of hormones and gene expression in Arabidopsis root development.…”