Differential effects of two phospholipase D inhibitors, 1-butanol and N-acylethanolamine, on in vivo cytoskeletal organization and Arabidopsis seedling growth

Abstract

Plant development is regulated by numerous chemicals derived from a multitude of metabolic pathways. However, we know very little about the biological effects and functions of many of these metabolites in the cell. N-Acylethanolamines (NAEs) are a group of lipid mediators that play important roles in mammalian physiology. Despite the intriguing similarities between animals and plants in NAE metabolism and perception, not much is known about the precise function of these metabolites in plant physiology. In plants, NAEs have been shown to inhibit phospholipase Dalpha (PLDalpha) activity, interfere with abscisic acid-induced stomatal closure, and retard Arabidopsis seedling development. 1-Butanol, an antagonist of PLD-dependent phosphatidic acid production, was reported to induce defects in Arabidopsis seedling development that were somewhat similar to effects induced by elevated levels of NAE. This raised the possibility that the impact of NAE on seedling growth could be mediated in part via its influence on PLD activity. To begin to address this possibility, we conducted a detailed, comparative analysis of the effects of 1-butanol and N-lauroylethanolamine (NAE 12:0) on Arabidopsis root cell division, in vivo cytoskeletal organization, seed germination, and seedling growth. Although both NAE 12:0 and 1-butanol induced profound cytoskeletal and morphological alterations in seedlings, there were distinct differences in their overall effects. 1-Butanol induced more pronounced modifications in cytoskeletal organization, seedling growth, and cell division at concentrations severalfold higher than NAE 12:0. We propose that these compounds mediate their differential effects on cellular organization and seedling growth, in part through the differential modulation of specific PLD isoforms.

Manipulation of Arabidopsis fatty acid amide hydrolase expression modifies plant growth and sensitivity to N -acylethanolamines

“…Functional homologues of the Arabidopsis FAAH (AtFAAH) also were identified in Oryza sativa and Medicago truncatula, supporting a common mechanism for the regulation of NAE hydrolysis in diverse plant species (15). To begin to understand the in vivo role of NAEs in plants, we generated Arabidopsis plants with altered AtFAAH expression and analyzed their response to an NAE type that we have previously shown to induce strong morphological effects on seedlings (9,10). Here, we demonstrate that the manipulation of AtFAAH activity alters the physiological responses of Arabidopsis seedlings to exogenously applied NAEs.…”

“…To determine whether Arabidopsis lacking endogenous FAAH activity displayed shifts in sensitivity toward exogenous NAEs, we germinated AtFAAH knockouts in a range of NAE12:0 concentrations. We showed previously that exogenous NAE12:0 resulted in severe inhibitory effects on Arabidopsis seedling growth, manifested as reduced cotyledon expansion and shorter hypocotyls and primary roots (9,10). Therefore, the distinct morphological effects induced by NAE12:0 provided us with a clear biological assay by which to test in vivo AtFAAH function and sensitivity to NAE.…”

“…These observations suggest that the rapid metabolism of NAEs during seed germination might be necessary for normal seedling development. In fact, exogenous application of N-lauroylethanolamine (NAE12:0), a naturally occurring plant NAE, inhibits seedling growth, alters cell shape, and influences cytoskeletal dynamics in Arabidopsis (9,10).…”

Effect of n-butanol and cold pretreatment on the cytoskeleton and the ultrastructure of maize microspores when cultured in vitro

“…While long exposures to n-butanol effectively slows or even blocks growth and development in Arabidopsis seedlings (Gardiner et al 2003;Motes et al 2005), shorter treatments with similar concentration resulted in elevated androgenic induction in wheat (Soriano et al 2008;Broughton 2011), maize (Földesiné Füredi et al 2011) and barley (Castillo et al 2014) microspore and anther cultures. As reported in barley microspore culture, n-butanol may act in a genotype-and pretreatmentdependent manner (Castillo et al 2014).…”

A Class I ADP-Ribosylation Factor GTPase-Activating Protein Is Critical for Maintaining Directional Root Hair Growth in Arabidopsis

“…In Arabidopsis root hairs, for example, RabA4b specifically interacts with a phosphatidylinositol 4-OH kinase at the tip, and this interaction has been proposed to be relevant for maintaining the cytoplasmic calcium gradient that drives polar root hair growth (Preuss et al, 2006). In this regard, inhibiting the production of lipid signaling molecules such as phosphatidic acid disrupted tip growth, disorganized the actin cytoskeleton, and dissipated the tip-focused cytoplasmic calcium gradient (Potocký et al, 2003;Monteiro et al, 2005;Motes et al, 2005). Also, a mutation in an Arabidopsis phosphatidylinositol transfer protein compromised polarized growth in root hairs, which coincided with a disorganization of the microtubule cytoskeleton (Vincent et al, 2005).…”