Polyamine metabolism influences antioxidant defense mechanism in foxtail millet (Setaria italica L.) cultivars with different salinity tolerance

Abstract

Polyamines can regulate the expression of antioxidant enzymes and impart plants tolerance to abiotic stresses. A comparative analysis of polyamines, their biosynthetic enzymes at kinetic and at transcriptional level, and their role in regulating the induction of antioxidant defense enzymes under salt stress condition in two foxtail millet (Setaria italica L.) cultivars, namely Prasad, a salt-tolerant, and Lepakshi, a salt-sensitive cultivar was conducted. Salt stress resulted in elevation of free polyamines due to increase in the activity of spermidine synthase and S-adenosyl methionine decarboxylase enzymes in cultivar Prasad compared to cultivar Lepakshi under different levels of NaCl stress. These enzyme activities were further confirmed at the transcript level via qRT-PCR analysis. The cultivar Prasad showed a greater decrease in diamine oxidase and polyamine oxidase activity, which results in the accumulation of polyamine pools over cultivar Lepakshi. Generation of free radicals, such as O 2 (·-) and H2O2, was also analyzed quantitatively. A significant increase in O 2 (·-) and H2O2 in the cultivar Lepakshi compared with cultivar Prasad was recorded in overall pool sizes. Further, histochemical staining showed lesser accumulation of O 2 (·-) and of H2O2 in the leaves of cultivar Prasad than cultivar Lepakshi. Our results also suggest the ability of polyamine oxidation in regulating the induction of antioxidative defense enzymes, which involve in the elimination of toxic levels of O 2 (·-) and H2O2, such as Mn-superoxide dismutase, catalase and ascorbate peroxidase. The contribution of polyamines in modulating antioxidative defense mechanism in NaCl stress tolerance is discussed.

Relationship between H2O2 in Polyamine Metabolism and Lignin in the Exocarp of a Russet Mutant of ‘Dangshansuli’ Pear (Pyrus bretschneideri Rehd.)

“…After pathogen invasion of barley and foxtail millet cells, large amounts of polyamines were synthesized, and the activities of the enzymes DAO and PAO were clearly increased, resulting in increased H 2 O 2 levels (Yordanova et al 2003;Sudhakar et al 2015). Polyamines in the PAO gene RNAi cell line were not degraded but secreted into the medium, and, under those conditions, the amount of H 2 O 2 produced was low (Yoda et al 2006).…”

Adaptation of Foxtail Millet (Setaria italica L.) to Abiotic Stresses: A Special Perspective of Responses to Nitrogen and Phosphate Limitations

“…Foxtail millet is a herbicide (Zhu et al, 2006) and is a drought and salt-tolerant crop (Jayaraman et al, 2008;Krishnamurthy et al, 2014;Sudhakar et al, 2015). Foxtail millet produces 1 g of dry mass at the cost of 257 g of water, which is far less than that required by maize and wheat (Li and Brutnell, 2011).…”

Modulation of antioxidant defense system and polyamine catabolism in rice leaves under two planting conditions

“…In general, when cellular PA contents are increased, their catabolism also increased which leads to the enhancement of ROS especially H 2 O 2 , hence their role in preventing the cellular damage is customary (Gill and Tuteja 2010). In fact, PAs may also be involved in activating APX, GPX and SOD activities thereby elevating antioxidant levels (ascorbate, α-tocopherol), to diminish free radical generation and thereby prevent membrane collapse (Yang et al 2007;Zhang et al 2009;Sudhakar et al 2015). Although, PAs enhances the expression of antioxidant enzymes at the translational level (Jaleel et al 2009), higher ability of tolerant plants to upregulate antioxidative genes reflect the involvement of reduced glutathione content mediated by glutathione reductase activity (Noctor and Foyer 1998).…”