Cellular Responses to Auxin: Division versus Expansion

Abstract

The phytohormone auxin is a major regulator of plant growth and development. Many aspects of these processes depend on the multiple controls exerted by auxin on cell division and cell expansion. The detailed mechanisms by which auxin controls these essential cellular responses are still poorly understood, despite recent progress in the identification of auxin receptors and components of auxin signaling pathways. The purpose of this review is to provide an overview of the present knowledge of the molecular mechanisms involved in the auxin control of cell division and cell expansion. In both cases, the involvement of at least two signaling pathways and of multiple targets of auxin action reflects the complexity of the subtle regulation of auxin-mediated cellular responses. In addition, it offers the necessary flexibility for generating differential responses within a given cell depending on its developmental context.

Rice actin-binding protein RMD is a key link in the auxin–actin regulatory loop that controls cell growth

“…Treatment with 10 nM IAA induced cell elongation, whereas 10 μM IAA inhibited cell elongation in WT roots ( Fig. 1 E and F), consistent with its concentration-dependent mode of action (24). However, the effect of IAA treatments in rmd-1 roots was attenuated compared with WT ( Fig.…”

Mechanisms of disruption of meristematic competence by microgravity inArabidopsisseedlings

“…Low levels of auxin induce cell elongation, enlargement, and differentiation; whereas high levels of auxin stimulate cell proliferation and cell cycle progression. 8,11 As a consequence, the role of auxin as a mediator of the maintenance of meristematic competence under normal gravity conditions would be modified in response to the change in the environmental gravity conditions. 9…”

“…5,6 These were relevant findings, since the alteration of cell growth and proliferation in the root meristem (the so-called "meristematic competence" 7 ) may have consequences at the level of development and shaping of the whole plant. 8 Furthermore, auxin regulation may link these cellular alterations in the meristem with the gravitropic signal perceived by columella cells in the root tip. When the environmental gravity conditions change, a transduction cascade results in the modification of the levels and distribution of auxin throughout the root.…”

Inhibition of Cell Expansion by Rapid ABP1-Mediated Auxin Effect on Microtubules? A Critical Comment

“…There is, on the other hand, ample evidence for a causal relationship between wall-relaxing processes (such as the secretion or activation of wall-loosening enzymes or the generation of reactive oxygen species) and the rapid regulation of cell growth by auxin (Cosgrove, 2005;Perrot-Rechenmann, 2010). Modification of the allometric ratio by changing the orientation of newly deposited cellulose microfibrils appears much too slow (happening over hours) to account for the inhibition of cell expansion within minutes (Evans et al, 1994).…”