The Winner Takes It All: Auxin—The Main Player during Plant Embryogenesis

Abstract

In plants, the first asymmetrical division of a zygote leads to the formation of two cells with different developmental fates. The establishment of various patterns relies on spatial and temporal gene expression, however the precise mechanism responsible for embryonic patterning still needs elucidation. Auxin seems to be the main player which regulates embryo development and controls expression of various genes in a dose-dependent manner. Thus, local auxin maxima and minima which are provided by polar auxin transport underlie cell fate specification. Diverse auxin concentrations in various regions of an embryo would easily explain distinct cell identities, however the question about the mechanism of cellular patterning in cells exposed to similar auxin concentrations still remains open. Thus, specification of cell fate might result not only from the cell position within an embryo but also from events occurring before and during mitosis. This review presents the impact of auxin on the orientation of the cell division plane and discusses the mechanism of auxin-dependent cytoskeleton alignment. Furthermore, close attention is paid to auxin-induced calcium fluxes, which regulate the activity of MAPKs during postembryonic development and which possibly might also underlie cellular patterning during embryogenesis.

Cytoskeletal regulation of primary plant cell wall assembly

“…These extracellular events are transmitted through the coupling between the cell wall and the microtubules. In addition to mechanical cues, microtubules are suggested to reorient in response to the application of hormones such as ethylene 134 , brassinosteroid 135 and auxin 136,137 . These relationships can be complex and overlapping.…”

From Single Cell to Plants: Mesophyll Protoplasts as a Versatile System for Investigating Plant Cell Reprogramming

“…Hormones are a key signal for stimulating cell reprogramming. Among the hormones, auxins are not only required for cell cycle activation [ 92 ] and essential for the induction of chromatin relaxation and DNA replication [ 80 ] but are also indispensable for somatic embryogenesis in general [ 93 ]. Cytokinins are key hormones that are involved in the process of cytokinesis.…”

Genome-Wide Analysis, Modeling, and Identification of Amino Acid Binding Motifs Suggest the Involvement of GH3 Genes during Somatic Embryogenesis of Coffea canephora

“…Auxin, in its free form, acts as a signal molecule [ 4 , 5 ]. Auxins play an essential role during cellular and vascular differentiation, phototropism, plant morphology, and somatic and zygotic embryogenesis [ 3 , 6 , 7 ]. Their endogenous levels are controlled by various regulatory mechanisms such as de novo biosynthesis, transport, irreversible degradation, and reversible inactivation mediated by indole-3-acetic acid (IAA) conjugation [ 8 , 9 ].…”