Aphid-stimulated transcriptional reconfigurations of chlorophyllase-2 gene in maize (Zea mays L.) seedlings

The purpose of the survey was to evaluate impact of bird cherry-oat aphid (Rhopalosiphum padi L.) herbivory on transcriptional responses of chlorophyllase-2 (CLH2) gene, total activity of chlorophyllase (CLH) enzyme and content of chlorophyll a in maize (Zea mays L.) leaves. Insect infestation assays were performed on 14-day-old seedlings of six maize varieties (i.e., Ambrozja and Waza – highly resistant; Eleganza and Touran – intermediately resistant; Tasty Sweet and Złota Karłowa – sensitive towards the examined aphids). Maize plants were artificially infested with mature wingless females of R. padi. Abundance of CLH2 transcript was quantified with the use of real-time qRT-PCR technique, whereas chlorophyllase activity and amount of the tested pigments were estimated using microplate spectrophotometric methods. Aphids' feeding markedly upregulated relative expression of CLH2 gene and enhanced total activity of CLH in maize seedlings. Conversely, hemipterans' attack caused significant depletion in content of chlorophyll a in tested plants. Considerably stronger effect of R. padi colonization on level of all tested parameters was found in seedling leaves of susceptible maize cultivars in comparison with more resistant ones. This is the first survey unravelling insect-stimulated modulations in both expression of CLH2 gene and chlorophyllase activity in tissues of maize genotypes displaying divergent resistance to aphids’ infestation.