Polyamines as key regulatory players in plants under metal stress—A way for an enhanced tolerance

Abstract

Polyamine (PA) metabolism and functions have started to raise attention from plant scientists in the last years. PAs have been investigated for their involvement in plant cell signalling and protection, proving that alterations in their endogenous levels can affect plant growth, development and survival. The recognised roles of PAs in metal‐stressed plants are presented and discussed on a “case‐study” basis, for each metal. Bearing in mind that the contamination of soils by heavy metals (HMs) is a growing problem worldwide, it is important to find efficient mechanisms through which agricultural productivity and food quality are safeguarded in a scenario of increased pollution. Making cultivars more tolerant to HM‐stress, capable of detoxifying or accumulating them safely, is a goal that will most certainly benefit from researching the functions and applicability of PAs. To date, plant PAs have been recognised for their roles as membrane‐, protein‐ and nucleic acid‐stabilisers, as protectors of cellular integrity and photosynthetic machinery, as direct and indirect signalling agents, and as emerging members of the non‐enzymatic antioxidant system. Moreover, PAs are not only important in normal plant developmental processes but have also been suggested to induce stress priming, to act as epigenetic regulators of gene expression and to enhance the detoxification and vacuolar compartmentalization of HMs. Although the stress‐ameliorating effects of PAs have been widely studied for several abiotic stresses, not much is known regarding their effects on metal induced‐stress, except for Cd. This review summarises the available work on the effects of PAs in plants exposed to Cu, Cd, Fe, Mn, Cr, Ni, Hg, Al, Pb and Zn.

Exogenous arginine modulates leaf antioxidant enzymes and hydrogen peroxide content in tomato plants under transient heat stresses

“…For instance, the foliar application of PAs on two wheat varieties under heat stress decreased both grain damages and MDA content while enhancing the activity of antioxidant enzymes, such as SOD and CAT (Jing et al 2020). Modifications in APX activity also occur simultaneously to alterations in PAs content and type, evidencing close relation between PAs and antioxidant enzymes (Spormann et al 2021). However, with the current data, the mechanism by which arginine modulates antioxidant machinery cannot be clearly established.…”

“…The PAs have multiple roles in plant development, likely due to their ability to regulate DNA replication, transcription and translation; cell proliferation; enzyme activities; cellular cation-anion balance and membrane stability (Gill and Tuteja 2010). Because PAs synthesis is increased in plants facing environmental challenges, and the use of different approaches to enhance the production PAs also lead to an improved plant tolerance to stresses (Chen et al 2019), PAs are considered natural alleviatory agents of the effects from nonoptimal environmental conditions on plants (Spormann et al 2021). For instance, the foliar application of PAs on two wheat varieties under heat stress decreased both grain damages and MDA content while enhancing the activity of antioxidant enzymes, such as SOD and CAT (Jing et al 2020).…”

Exogenous Nitric Oxide Confers Tolerance to Cr(VI) in Maize (Zea mays L.) Seedlings by Modulating Endogenous Oxido-Nitrosative Events

“…In plants, the most common free PAs are Spd and Spm as well as putrescine (Asghari and Abdollahi, 2013;Spormann et al 2020). Chromium was found to increase the accumulation of PAs in both radicles (2 and 5 times, compared to control, for Spd and Spm, respectively) (Fig.…”

“…nitrate reductase. The oxidative pathway of NO is interconnected with various signalling molecules and metabolites that perform important functions in plant stress responses including polyamines (PAs) and proline (Pro) (Spormann et al 2020). In plants, the existence of NO synthase (NOS)-like activity is still a controversial issue.…”

“…The PAs are known to act as an agent improving effects of NO (Asghari and Abdollahi 2013). Indeed, an over-accumulation of PAs in response to various environmental constraints can protect cellular structures, and detoxify free radicals, at least in part through the production of NO (Spormann et al 2020).…”