Putrescine Alleviates Iron Deficiency via NO-Dependent Reutilization of Root Cell-Wall Fe in Arabidopsis  

Abstract

Plants challenged with abiotic stress show enhanced polyamines levels. Here, we show that the polyamine putrescine (Put) plays an important role to alleviate Fe deficiency. The adc2-1 mutant, which is defective in Put biosynthesis, was hypersensitive to Fe deficiency compared with wild type (Col-1 of Arabidopsis [Arabidopsis thaliana]). Exogenous Put decreased the Fe bound to root cell wall, especially to hemicellulose, and increased root and shoot soluble Fe content, thus alleviating the Fe deficiency-induced chlorosis. Intriguingly, exogenous Put induced the accumulation of nitric oxide (NO) under both Fe-sufficient (+Fe) and Fe-deficient (-Fe) conditions, although the ferric-chelate reductase (FCR) activity and the expression of genes related to Fe uptake were induced only under -Fe treatment. The alleviation of Fe deficiency by Put was diminished in the hemicellulose-level decreased mutant-xth31 and in the noa1 and nia1nia2 mutants, in which the endogenous NO levels are reduced, indicating that both NO and hemicellulose are involved in Put-mediated alleviation of Fe deficiency. However, the FCR activity and the expression of genes related to Fe uptake were still up-regulated under -Fe+Put treatment compared with -Fe treatment in xth31, and Put-induced cell wall Fe remobilization was abolished in noa1 and nia1nia2, indicating that Put-regulated cell wall Fe reutilization is dependent on NO. From our results, we conclude that Put is involved in the remobilization of Fe from root cell wall hemicellulose in a process dependent on NO accumulation under Fe-deficient condition in Arabidopsis.

Exogenous Melatonin Improves Plant Iron Deficiency Tolerance via Increased Accumulation of Polyamine-Mediated Nitric Oxide

“…Consistently, the activities of ADC were significantly enhanced in the melatonin-treated plants compared with non-treated plants under +Fe and −Fe conditions (Figure S1). Recently, exogenous Put has been shown to improve the tolerance of Arabidopsis plants to Fe deficiency [36]. Thus, the melatonin-induced increase of polyamine levels indicated the possible involvement of melatonin in Fe deficiency responses of plants.…”

“…Similar results were found in this study showing exogenous melatonin rapidly induced the polyamine biosynthesis in Arabidopsis plants under +Fe and −Fe conditions. Recently, Zhu et al [36] have indicated that Put plays an important role in the regulation of Fe deficiency responses in Arabidopsis plants. Therefore, it seemed reasonable to assume that melatonin conferred the stronger ability of plants to tolerate Fe deficiency, possibly through regulation of polyamine metabolism.…”

“…It has previously been reported that polyamine can stimulate the biosynthesis of NO in Arabidopsis roots [35]. Furthermore, interruption of NO release has been shown to inhibit certain effects of polyamine on plants [36,50], indicating that NO acts as a downstream transducer of polyamine-mediated signaling pathways. Intriguingly, overproduction of NO can provoke toxic effects in plants [51].…”

“…Interestingly, exogenous polyamines, including putrescine (Put), spermidine (Spd), and spermine (Spm), can rapidly induce a significant increase of NO production in Arabidopsis plants [35], suggesting that NO is a key intermediate of polyamine-mediated signaling pathways. More recently, exogenous Put induces the accumulation of NO, thereby activating plant Fe deficiency responses and promoting Fe remobilization from the cell wall [36]. The cell wall is the major reservoir for root apoplastic Fe, and over 75% of Fe is stored in the cell wall of plant roots [37].…”

Enhanced Iron and Selenium Uptake in Plants by Volatile Emissions of Bacillus amyloliquefaciens (BF06)

“…Root NO accumulation was monitored using 4-amino-5-methylamino-2 , 7 -difluorofluorescein diacetate (DAF-FM DA) probes [48]. The samples were incubated in the solution containing 1.5 µM DAF-FM DA for 15 min, followed by three rinses with phosphate buffer saline (PBS, pH 7.4).…”