Abstract
The relationship between hydrogen peroxide and polyamine metabolism and the role of NADPH oxidase (NOX) in this relationship under drought conditions has not yet been clarified. To reveal the relationship, expression levels of the genes in polyamine metabolism, such as arginine decarboxylase (ADC), agmatine aminohydrolase (AIH), spermidine synthase (SPDS), S-adenosyl methionine decarboxylase (SAMDC), diamine oxidase (DAO) and polyamine oxidase (PAO) were determined by RT PCR under drought stress combined with exogenous hydrogen peroxide (H2O2) and diphenyleneiodonium chloride (DPI) treatments in maize seedlings. Also, some basic stress parameters (leaf water potential, lipid peroxidation), polyamine levels (putrescine, spermidine, and spermine), and gene expression of NOX were measured under drought stress. Exogenous H2O2 induced polyamine contents by up-regulating polyamine-synthesizing genes and downregulating polyamine oxidizing genes. Moreover, when the NOX enzyme was inhibited by DPI, the polyamine metabolic pathway tended toward degradation rather than production. Exogenous H2O2 regulated polyamine metabolism to promote their synthesis, and NOX had a key role in this regulation.
Highlights
Polyamines, similar to hormones, have been considered to function as regulatory molecules in several basic cellular and physiological processes such as cell division, differentiation, and proliferation, cell death, membrane stabilization, DNA replication, protein synthesis, flower formation and development, leaf senescence, fruit development and maturation, biotic and abiotic stress responses (Alcazar et al 2006a; Kusano et al 2008)
Water potential measurements were performed to determine the effect of H2O2 on the water content of maize plants subjected to drought stress conditions
Terzi et al (2014) determined that the water potential of the leaf increased in drought stress conditions with the application of H2O2 in maize plants compared to control (PEG only)
Summary
Polyamines, similar to hormones, have been considered to function as regulatory molecules in several basic cellular and physiological processes such as cell division, differentiation, and proliferation, cell death, membrane stabilization, DNA replication, protein synthesis, flower formation and development, leaf senescence, fruit development and maturation, biotic and abiotic stress responses (Alcazar et al 2006a; Kusano et al 2008). Recent studies of transgenic and mutant plants with excess or less polyamine suggest that polyamines play a protective role against abiotic stress (Alcazar et al 2006b; Kusano et al 2008; Gill & Tuteja 2010). In a study by Kusano et al (2007), Arabidopsis acl5/spms double mutant plants, which are unable to produce spermine, became hypersensitive to drought and saline stress. The externally applied spermine mitigated the effects of the stresses mentioned in the plant. Yamaguchi et al (2006, 2007) reported that the susceptibility to drought and salt stresses increased in the studies with double mutants of spms1/acl of Arabidopsis to investigate the protective role of spermine against abiotic stress
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