Abstract
Reduced forms of ascorbate (AsA) and glutathione (GSH) are among the most important non-enzymatic foliar antioxidants in maize (Zea mays L.). The survey was aimed to evaluate impact of bird cherry-oat aphid (Rhopalosiphum padi L.) or grain aphid (Sitobion avenae F.) herbivory on expression of genes related to ascorbate-glutathione (AsA-GSH) cycle in seedlings of six maize varieties (Ambrozja, Nana, Tasty Sweet, Touran, Waza, Złota Karłowa), differing in resistance to the cereal aphids. Relative expression of sixteen maize genes encoding isoenzymes of ascorbate peroxidase (APX1, APX2, APX3, APX4, APX5, APX6, APX7), monodehydroascorbate reductase (MDHAR1, MDHAR2, MDHAR3, MDHAR4), dehydroascorbate reductase (DHAR1, DHAR2, DHAR3) and glutathione reductase (GR1, GR2) was quantified. Furthermore, effect of hemipterans’ attack on activity of APX, MDHAR, DHAR and GR enzymes, and the content of reduced and oxidized ascorbate and glutathione in maize plants were assessed. Seedling leaves of more resistant Z. mays varieties responded higher elevations in abundance of target transcripts. In addition, earlier and stronger aphid-triggered changes in activity of APX, MDHAR, DHAR and GR enzymes, and greater modulations in amount of the analyzed antioxidative metabolites were detected in foliar tissues of highly resistant Ambrozja genotype in relation to susceptible Tasty Sweet plants.
Highlights
Ascorbic acid (AsA) and reduced glutathione (GSH; γ-L-glutamyl-L-cysteinylglycine) are major non-enzymatic and hydrophilic antioxidants in the leaves of maize (Zea mays L.) [1,2]
GSH is biosynthesized in plastids and cytosol, and it is being transported via unrecognized routes to the other subcellular locations [7], whereas AsA is produced in mitochondria, and subsequently, it is translocated to the other compartments or even extracellularly through the plasma membrane [8]
The greatest decreases in GSH level were noted in Ambrozja seedlings (10%–22% declines at 8 hpi; 12%–30% at 12 hpi; 25%–38% at 24 hpi), whereas the lowest depletion was recorded in Tasty Sweet plants (2%–5% declines at 8 hpi; 3%–8% at 12 hpi; 10%–15% at 24 hpi)
Summary
Ascorbic acid (AsA) and reduced glutathione (GSH; γ-L-glutamyl-L-cysteinylglycine) are major non-enzymatic and hydrophilic antioxidants in the leaves of maize (Zea mays L.) [1,2]. GSH is biosynthesized in plastids and cytosol, and it is being transported via unrecognized routes to the other subcellular locations [7], whereas AsA is produced in mitochondria, and subsequently, it is translocated to the other compartments or even extracellularly through the plasma membrane [8]. The content of these metabolites varies considerably between diverse plant systems, in dependence on genotype, developmental stage and organ, tissue and subcellular localization [3,7]. The intervarietal differences in the content of reduced and oxidized forms of glutathione and ascorbate (GSH and GSSG, AsA and DHA, respectively), as well as the ratios of GSH/GSSG and AsA/DHA in the aphid-infested plants were not reported so far
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