The Interplay among Polyamines and Nitrogen in Plant Stress Responses.

Konstantinos Paschalidis,Filippos Ververidis,Ji-Hong Liu,Costas Delis,Konstantinos Loulakakis,Muhammad Makky,Panagiotis F. Sarris,Georgios Tsaniklidis,Bao-Quan Wang,Emmanouil Trantas

doi:10.3390/plants8090315

Abstract

The interplay between polyamines (PAs) and nitrogen (N) is emerging as a key factor in plant response to abiotic and biotic stresses. The PA/N interplay in plants connects N metabolism, carbon (C) fixation, and secondary metabolism pathways. Glutamate, a pivotal N-containing molecule, is responsible for the biosynthesis of proline (Pro), arginine (Arg) and ornithine (Orn) and constitutes a main common pathway for PAs and C/N assimilation/incorporation implicated in various stresses. PAs and their derivatives are important signaling molecules, as they act largely by protecting and preserving the function/structure of cells in response to stresses. Use of different research approaches, such as generation of transgenic plants with modified intracellular N and PA homeostasis, has helped to elucidate a plethora of PA roles, underpinning their function as a major player in plant stress responses. In this context, a range of transgenic plants over-or under-expressing N/PA metabolic genes has been developed in an effort to decipher their implication in stress signaling. The current review describes how N and PAs regulate plant growth and facilitate crop acclimatization to adverse environments in an attempt to further elucidate the N-PAs interplay against abiotic and biotic stresses, as well as the mechanisms controlling N-PA genes/enzymes and metabolites.

Highlights

On the other hand, is catalyzed mainly by glutamate dehydrogenase (GDH); under stress conditions GDH partly contributes to ammonia assimilation [34,41]
Under threatening abiotic and biotic stress conditions, the plants respond by remobilizing N and C into signaling molecules, such as PAs, Pro, GABA, glycine betaine, and β-Ala [78], as they have stress-protective key roles and partly alleviate ammonia cell toxicity
It is further proposed that the polyamine oxidase (PAO)/NADPH oxidase loop is a focal point in the control of several defense processes in plants, including stress tolerance (Figure 1) [22,24,25,35,36]

Summary

Introduction

Polyamines (PAs), and several important plant phytohormones, such as ethylene, jasmonates, abscisic acid, salicylic acid, have shown to act as crucial growth regulators that can cross talk with each other in stress signaling processes [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]. Plants 2019, 8, 315 such as cell wall degradation [23] oxidative and developmental stress [2,24,25,26,27,28,29,30,31], phytopathogenic bacteria/fungi/viruses [30], water deficiency [31,32,33], ammonia toxicity and nutrient availability [34], salinity [2,35,36,37] and heat [38,39]. Repression of ZmPAO in young tobacco seedlings enables them to resist short-term salinity, which can be attributed either to higher PA content or to lower ROS contents, because of the perturbed PA apoplastic oxidation [27,28]. This review elucidates the concerted roles of N and PAs against plant abiotic and biotic stressors, as well as their interplay mechanisms, as far as the related genes/enzymes and metabolites are concerned, in order to help plants adapt to unfavorable environmental conditions

Major Genes Involved in Abiotic and Biotic Stress Responses

Stress-Related Nitrogen Flow and Polyamines

O2 levels form apoplastic “barrier”

Conclusion and Perspectives

Methods