Abstract
The purpose of this report was to evaluate the expression patterns of selected glutathione transferase genes (gst1, gst18, gst23 and gst24) in the tissues of two maize (Zea mays L.) varieties (relatively resistant Ambrozja and susceptible Tasty Sweet) that were colonized with oligophagous bird cherry-oat aphid (Rhopalosiphum padi L.) or monophagous grain aphid (Sitobion avenae L.). Simultaneously, insect-triggered generation of superoxide anion radicals (O2 •−) in infested Z. mays plants was monitored. Quantified parameters were measured at 1, 2, 4, 8, 24, 48 and 72 h post-initial aphid infestation (hpi) in relation to the non-infested control seedlings. Significant increases in gst transcript amounts were recorded in aphid-stressed plants in comparison to the control seedlings. Maximal enhancement in the expression of the gst genes in aphid-attacked maize plants was found at 8 hpi (gst23) or 24 hpi (gst1, gst18 and gst24) compared to the control. Investigated Z. mays cultivars formed excessive superoxide anion radicals in response to insect treatments, and the highest overproduction of O2 •− was noted 4 or 8 h after infestation, depending on the aphid treatment and maize genotype. Importantly, the Ambrozja variety could be characterized as having more profound increments in the levels of gst transcript abundance and O2 •− generation in comparison with the Tasty Sweet genotype.
Highlights
Maize (Zea mays L.) has increasingly emerged as a pivotal model plant species (Poaceae family, Panicoideae subfamily) that is widely used in a variety of genetic and ecotoxicological experiments [1,2,3]
R. padi–stressed Tasty Sweet plants generated 2–26% more O2N2 than seedlings attacked by S. avenae, whereas R. padi–stressed Ambrozja plants had 4–91% greater rates of O2N2 formation than S. avenae–infested seedlings
Maximal O2N2 formation was observed at 4 hpi in Tasty Sweet seedlings infested with 60 individuals of bird cherry-oat aphid or grain aphid, and in Ambrozja seedlings colonized with 20–60 R. padi or 40–60 S. avenae aphids per plant
Summary
Maize (Zea mays L.) has increasingly emerged as a pivotal model plant species (Poaceae family, Panicoideae subfamily) that is widely used in a variety of genetic and ecotoxicological experiments [1,2,3]. Among the numerous insects attacking Z. mays plants, destructive influence of cereal aphids (Hemiptera, Aphidoidea) colonization should be underlined [6,7,8]. These phloem feeding parasites are involved in severe exploitation of the host systems, resulting in a broad range of detrimental effects, such as mechanical injuries of the stylet-penetrated tissues, local chlorosis or necrosis, deformations of organs, biomass reduction, significant disturbances of cellular homeostasis and transmission of pathogenic viruses. It has been documented that cereal aphids evoked a significant decrease in ascorbate content in triticale and deterioration of the antioxidative capacity toward DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals in maize plants [6,16]. It should be noted that cellular redox imbalance in plant cells due to a chronic overproduction of various reactive oxygen species (ROS) may result in profound oxidative damages of lipids, polysaccharides, proteins and nucleic acids [15,16]
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