Abstract
BackgroundMaize (Zea mays L.) is a major cereal crop, with the United States accounting for over 40% of the worldwide production. Corn leaf aphid [CLA; Rhopalosiphum maidis (Fitch)] is an economically important pest of maize and several other monocot crops. In addition to feeding damage, CLA acts as a vector for viruses that cause devastating diseases in maize. We have shown previously that the maize inbred line Mp708, which was developed by classical plant breeding, provides heightened resistance to CLA. However, the transcriptomic variation conferring CLA resistance to Mp708 has not been investigated.ResultsIn this study, we contrasted the defense responses of the resistant Mp708 genotype to those of the susceptible Tx601 genotype at the transcriptomic (mRNA-seq) and volatile blend levels. Our results suggest that there was a greater transcriptomic remodeling in Mp708 plants in response to CLA infestation compared to the Tx601 plants. These transcriptomic signatures indicated an activation of hormonal pathways, and regulation of sesquiterpenes and terpenoid synthases in a constitutive and inducible manner. Transcriptomic analysis also revealed that the resistant Mp708 genotype possessed distinct regulation of ethylene and jasmonic acid pathways before and after aphid infestation. Finally, our results also highlight the significance of constitutive production of volatile organic compounds (VOCs) in Mp708 and Tx601 plants that may contribute to maize direct and/or indirect defense responses.ConclusionsThis study provided further insights to understand the role of defense signaling networks in Mp708’s resistance to CLA.
Highlights
Maize (Zea mays L.) is a major cereal crop, with the United States accounting for over 40% of the worldwide production
We have previously shown that the maize inbred line Mp708, which was developed by classical plant breeding from a cross between the insect resistant Mp704 and susceptible Tx601 plants, provides heightened resistance to Corn Leaf Aphid (CLA) [12,13,14,15]
Our results suggest that the resistant Mp708 genotype uniquely activates different pathways involved in plant defense mechanisms before and after aphid infestation that may contribute to resistance to CLA, whereas the modulation of defense pathways before or after aphid infestation were not accompanied by enhanced defense against CLA in the susceptible Tx601 genotype
Summary
Maize (Zea mays L.) is a major cereal crop, with the United States accounting for over 40% of the worldwide production. Corn leaf aphid [CLA; Rhopalosiphum maidis (Fitch)] is an economically important pest of maize and several other monocot crops. In addition to feeding damage, CLA acts as a vector for viruses that cause devastating diseases in maize. Corn leaf aphid [CLA; Rhopolosiphum maidis (Fitch)] is the most commonly found sap-sucking insect pest on maize [2, 6]. Apart from causing direct yield loss, CLA feeding acts as a vector for viruses such as maize dwarf mosaic virus and maize leaf fleck virus [9, 10]. CLA feeding covers maize plants with honeydew (the digestive waste product of aphids), that leaves a sticky deposit on the plants and causes mold, thereby disrupting and/or reducing photosynthetic efficiency [11]
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