Abscisic acid-induced nitric oxide and proline accumulation in independent pathways under water-deficit stress during seedling establishment in Medicago truncatula

Abstract

Nitric oxide (NO) production and amino acid metabolism modulation, in particular abscisic acid (ABA)-dependent proline accumulation, are stimulated in planta by most abiotic stresses. However, the relationship between NO production and proline accumulation under abiotic stress is still poorly understood, especially in the early phases of plant development. To unravel this question, this work investigated the tight relationship between NO production and proline metabolism under water-deficit stress during seedling establishment. Endogenous nitrate reductase-dependent NO production in Medicago truncatula seedlings increased in a time-dependent manner after short-term water-deficit stress. This water-deficit-induced endogenous NO accumulation was mediated through a ABA-dependent pathway and accompanied by an inhibition of seed germination, a loss of water content, and a decrease in elongation of embryo axes. Interestingly, a treatment with a specific NO scavenger (cPTIO) alleviated these water-deficit detrimental effects. However, the content of total amino acids, in particular glutamate and proline, as well as the expression of genes encoding enzymes of synthesis and degradation of proline were not affected by cPTIO treatment under water-deficit stress. Under normal conditions, exogenous NO donor stimulated neither the expression of P5CS2 nor the proline content, as observed after PEG treatment. These results strongly suggest that the modulation of proline metabolism is independent of NO production under short-term water-deficit stress during seedling establishment.

The time course of NO involved in ABA pathway to improve drought tolerance in Oxytropis ochrocephala Bunge

“…This implies that NO acts downstream of ABA that is consistent with previous evidences for the cross-talk between ABA and NO signaling pathways under drought stress (Hancock et al 2011;Lu et al 2014). Although ABA or ABA biosynthesis inhibitor could directly influence endogenous NO and proline contents, the proline accumulation was unaffected by NO donor and endogenous NO scavenger, which confirmed the hypothesis that NO may not linear with proline (Planchet et al 2014). Moreover, the MDA levels not only increased in PEG ?…”

ABA mediates PEG-mediated premature differentiation of root apical meristem in plants

“…[5][6][7] It has shown that high levels of ABA at micromolar inhibit root growth, whereas lower levels of ABA stimulate root growth. A recent study showed that root growth stimulation by low concentration of ABA is .…”

Plant Responses to Salt Stress: Adaptive Mechanisms

“…In plants, proline synthesis is mainly catalysed by ∆-1-pyrroline-5-carboxylate synthetase (P5CS; EC 2.7.2.11/1.2.1.41), which converts glutamate into ∆-1-pyrroline-5-carboxylate (P5C) in the cytoplasm or chloroplast. P5C reductase (P5CR) further reduces P5C to proline [169]. In addition, proline may be also synthesised in mitochondria from ornithine by ornithine δ-aminotransferase (OAT; EC 2.6.1.13), catalysing the formation of P5C, which is further reduced to proline by P5CR.…”