Nitric oxide modulates polyamine homeostasis in sunflower seedling cotyledons under salt stress

Abstract

Free polyamine (PA) titers in plants may be regulated through reversible conjugate formation and/or through modulation of their synthesis, transport and degradation. PA signaling involves the wellacknowledged signaling molecule, nitric oxide (NO), which functions in diverse biological processes. Present investigations demonstrate the influence of salt stress (120 mM NaCl) and exogenous NO donor (250 µM Diethylenetriamine, DETA) on PA homeostasis of 2 d old, etiolated sunflower (Helianthus annuus L.) seedling cotyledons as a long-distance signaling response. Significantly enhanced intracellular spermine (Spm) accumulation was observed in seedling cotyledons under salt stress and in response to NO donor, the increase being more pronounced in seedlings treated with NO, evidently as a result of upregulation of the PA biosynthetic enzymesarginine decarboxylase (ADC) and S-adenosylmethionine decarboxylase (SAMDC)as revealed by Western blot and confocal imaging (CLSM). Moreover, salt stress induced the activity of polyamine oxidase (PAO), a PA catabolic enzyme, while NO lowered its activity in salt-stressed seedling cotyledons. NO, thus, appears to assist the seedlings in adapting to salt stress by positively regulating PA homeostasis through regulation of PA distribution between free, conjugated and bound forms, increased accumulation of PA biosynthetic enzymes and lowering the rate of PA catabolism.

Advances in Understanding of Desiccation Tolerance of Lichens and Lichen-Forming Algae

“…NO is a key intra- and intercellular signaling molecule in a very broad range of organisms, from animals to plants [ 185 ]. In the latter, NO has been found to be involved in the control of diverse biochemical and physiological responses to stress such as pathogens [ 186 ], salt [ 187 ], temperature [ 188 ] and drought [ 189 ]. Downstream, NO can lead to post-translational modification of proteins through S-nitrosation [ 190 ] and tyrosine nitration [ 191 ], tuning their enzymatic activities.…”

Molecular functions of nitric oxide and its potential applications in horticultural crops

“…NO was recently proposed to mediate the plant response to salt stress on the basis of its toxicity and signaling functions. Under salt stress, NO has been found to improve seed germination and plant growth of pak choi ( B. chinensis ), sunflower ( Helianthus annuus ), and cucumber by alleviating oxidative stress or regulating secondary metabolism 90 , 147 , 148 . In recent years, attention has been given to the NO-dependent PTM of proteins in response to salt stress.…”

Unravelling ties in the nitrogen network: Polyamines and nitric oxide emerging as essential players in signalling roadway

“…For instance, it was observed that exogenous application of NO (as SNP) enhanced chilling tolerance of banana fruits and bamboo shoots, by upregulating ADC and ODC genes and enzyme activities and thus increasing PAs content, in a response also mediated by GABA and Pro (Wang, Luo, Mao, & Ying, 2016; Wang et al, 2017). It was also observed higher Spm levels in sunflower seedling cotyledons under salt stress treated with NO as compared with saline treatment alone, because of upregulation of the PA biosynthetic enzymes ADC and SAMDC (Tailor, Tandon, & Bhatla, 2019). Although NO donor application significantly increased the production of Spm, it did not alter the level of free Spm but enhanced the proportion of conjugated and bound Spm, irrespective of salt stress.…”

“…Despite there being much evidence supporting the fact that NO and PAs can stimulate each other's production, it appears that PAs depend on NO as a downstream signal to trigger various stress responsive mechanisms to improve stress tolerance, not exerting their effects by themselves, at least under certain circumstances. Several reports have demonstrated that exogenous PA treatment result in a higher level of NO in plants (Tun et al, 2006; Groppa et al, 2008; Rosales et al, 2011, 2012; Diao et al, 2016; Diao et al, 2017; Recalde et al, 2018), whereas it was shown that NO influences PAs metabolism (Diao et al, 2016; Diao et al, 2017; Gong et al, 2014; Groppa et al, 2008; Wang et al, 2016; Wang et al, 2017; Tailor et al, 2019).…”