Epigenetic Regulation of Auxin Homeostasis

Abstract

Epigenetic regulation involves a myriad of mechanisms that regulate the expression of loci without altering the DNA sequence. These different mechanisms primarily result in modifications of the chromatin topology or DNA chemical structure that can be heritable or transient as a dynamic response to environmental cues. The phytohormone auxin plays an important role in almost every aspect of plant life via gradient formation. Auxin maxima/minima result from a complex balance of metabolism, transport, and signaling. Although epigenetic regulation of gene expression during development has been known for decades, the specific mechanisms behind the spatiotemporal dynamics of auxin levels in plants are only just being elucidated. In this review, we gather current knowledge on the epigenetic mechanisms regulating the expression of genes for indole-3-acetic acid (IAA) metabolism and transport in Arabidopsis and discuss future perspectives of this emerging field.

Keywords: auxin biosynthesis; auxin homeostasis; auxin transport; epigenetics.

Figure 1

Auxin biosynthesis and transport are epigenetically regulated along the plant life cycle. (a–h) Epigenetic regulation of (a–e) auxin-biosynthesis-related genes and (f–i) auxin-transport-related genes. Colored ovals represent proteins of the epigenetic machinery: chromatin remodelers (red), Polycomb and other histone modifiers (green), DNA methylation/demethylation enzymes (grey), histone chaperones (yellow), and noncoding RNAs (pink). Pale orange rectangles indicate transcription factors. Proteins promoting gene activation are represented above the gene, whereas factors drawn below represent repressors. Distances to the regulated gene are not drawn to scale.