Non‐specificity of ethylene inhibitors: ‘double‐edged’ tools to find out new targets involved in the root morphogenetic programme

Abstract

In the last decade, genetic and pharmacological approaches have been used to explore ethylene biosynthesis and perception in order to study the role of ethylene and ethylene/auxin interaction in root architecture development. However, recent findings with pharmacological approaches highlight the non-specificity of commonly used inhibitors. This suggests that caution is required for interpreting these studies and that the use of pharmacological agents is a 'double-edged' tool. On one hand, non-specific effects make interpretation difficult unless other experiments, such as with different mutants or with multiple diversely acting chemicals, are conducted. On the other hand, the non-specificity of inhibitors opens up the possibility of uncovering some ligands or modulators of new receptors such as plant glutamate-like receptors and importance of some metabolic hubs in carbon and nitrogen metabolism such as the pyridoxal phosphate biosynthesis involved in the regulation of the root morphogenetic programme. Identification of such targets is a critical issue to improve the efficiency of absorption of macronutrients in relation to root the morphogenetic programme.

AtDAT1 is a key enzyme of D-amino acid stimulated ethylene production inArabidopsis thaliana

“…They are also able to conjugate ACC with glutathione to γ-glutamyl-ACC (GACC) and with jasmonic acid to JA-ACC to control the ACC content. Additionally, plants can degrade ACC irreversibly by an ACC deaminase α-ketobutyrate (for reviews about ACC content regulation see Van de Poel and Van Der Straeten (2014), Le Deunff and Lecourt (2016), and Vanderstraeten and Van Der Straeten (2017)). To date neither the contribution of each of these ACC degradation pathways to control the ACC pool nor their interplay has been studied, yet.…”

AtDAT1 Is a Key Enzyme of D-Amino Acid Stimulated Ethylene Production in Arabidopsis thaliana

“…There is also the possibility that ACC is conjugated with glutathione to g-glutamyl-ACC (GACC) and with jasmonic acid to JA-ACC to control the ACC homeostasis. Additionally, plants can irreversibly degrade ACC to a-ketobutyrate by an ACC deaminase [for reviews about ACC content regulation, see Van de Poel and Van Der Straeten (2014); Le Deunff and Lecourt (2016), and Vanderstraeten and Van Der Straeten (2017)]. To date, neither the contribution of each of these ACC catabolic pathways nor their interplay for the control of ACC homeostasis have been studied, yet.…”

Inhibition of Aminotransferases by Aminoethoxyvinylglycine Triggers a Nitrogen Limitation Condition and Deregulation of Histidine Homeostasis That Impact Root and Shoot Development and Nitrate Uptake

“…Inhibitors of aminotransferases such as aminoethoxyvinyl-glycine (AVG), Rhizobitoxine and aminooxyacetic acid (AOA) have recently been demonstrated to be non-specific, possessing a broad inhibitory spectrum (Berkowitz et al, 2006; Soeno et al, 2010; Le Deunff and Lecourt, 2016; Le Deunff, 2018). This offers the possibility to highlight the effects of nitrogen metabolism impairment on the root and shoot morphogenetic program and root nitrate uptake (Le Deunff and Lecourt, 2016; Le Deunff et al, 2016).…”

“…Inhibitors of aminotransferases such as aminoethoxyvinyl-glycine (AVG), Rhizobitoxine and aminooxyacetic acid (AOA) have recently been demonstrated to be non-specific, possessing a broad inhibitory spectrum (Berkowitz et al, 2006; Soeno et al, 2010; Le Deunff and Lecourt, 2016; Le Deunff, 2018). This offers the possibility to highlight the effects of nitrogen metabolism impairment on the root and shoot morphogenetic program and root nitrate uptake (Le Deunff and Lecourt, 2016; Le Deunff et al, 2016). Indeed, nitrogen nutrition and plant development depend not only on nitrate uptake and reduction, but also on the assimilation of nitrogen into amino acids, nucleic acid bases, proteins, polyamines, chlorophylls and hormones due to the action of many aminotransferases downstream the GS/GOGAT cycle (Stitt et al, 2002; Lea and Azevedo, 2006).…”

“…Despite the essential role played by TAA , TARs and ACS aminotransferases in the root morphogenetic program (Rahman et al, 2000; Stepanova et al, 2008; Tao et al, 2008; Okamoto et al, 2008; Yamada et al, 2009; Ma et al, 2014; Sugawara et al, 2015), the involvement of other aminotransferases within subgroup I of the α family on root development has been overlooked (Le Deunff et al, 2016; Le Deunff, 2018). Arabidopsis mutants of aminotransferases of N metabolism such as aspartate aminotransferase ( AAT ), alanine aminotransferase ( AlaAT ) and histidinol phosphate aminotransferase ( HPA ) displayed root developmental defects (Schultz et al, 1998; Miesak and Coruzzi, 2002; McAllister and Good, 2015; Mo et al, 2006).…”