Differential Expression of Superoxide Dismutase Genes in Aphid-Stressed Maize (<i>Zea mays</i> L.) Seedlings

<div><p>The aim of this study was to compare the expression patterns of superoxide dismutase genes (<i>sod2</i>, <i>sod3.4</i>, <i>sod9</i> and <i>sodB</i>) in seedling leaves of the <i>Zea mays</i> L. Tasty Sweet (susceptible) and Ambrozja (relatively resistant) cultivars infested with one of two hemipteran species, namely monophagous <i>Sitobion avenae</i> F. (grain aphid) or oligophagous <i>Rhopalosiphum padi</i> L. (bird cherry-oat aphid). Secondarily, aphid-elicited alternations in the antioxidative capacity towards DPPH (1,1-diphenyl-2-picrylhydrazyl) radical in insect-stressed plants were evaluated. Comprehensive comparison of expression profiles of the four <i>sod</i> genes showed that both insect species evoked significant upregulation of three genes <i>sod2</i>, <i>sod3.4</i> and <i>sod9</i>). However, aphid infestation affected non-significant fluctuations in expression of <i>sodB</i> gene in seedlings of both maize genotypes. The highest levels of transcript accumulation occurred at 8 h (<i>sod2</i> and <i>sod3.4</i>) or 24 h (<i>sod9</i>) post-infestation, and aphid-induced changes in the expression of <i>sod</i> genes were more dramatic in the Ambrozja cultivar than in the Tasty Sweet variety. Furthermore, bird cherry-oat aphid colonization had a more substantial impact on levels of DPPH radical scavenging activity in infested host seedlings than grain aphid colonization. Additionally, Ambrozja plants infested by either hemipteran species showed markedly lower antioxidative capacity compared with attacked Tasty Sweet plants.</p>