Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA.
Wheat, Sorghum, and Forage Research Unit, USDA-ARS, Lincoln, NE, 68583, USA.
BMC Plant Biol. 2021 Mar 16;21(1):138. doi: 10.1186/s12870-021-02910-0.
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. 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.
In 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.
This study provided further insights to understand the role of defense signaling networks in Mp708's resistance to CLA.
玉米（Zea mays L.）是一种主要的谷类作物，美国的玉米产量占世界总产量的 40%以上。玉米叶蝉[CLA；Rhopalosiphum maidis（Fitch）]是玉米和其他几种单子叶作物的一种重要经济害虫。除了取食造成的损害外，CLA 还充当病毒的载体，这些病毒会导致玉米毁灭性的疾病。我们之前已经表明，通过传统植物育种开发的玉米自交系 Mp708 对 CLA 具有增强的抗性。然而，赋予 Mp708 抗 CLA 能力的转录组变异尚未得到研究。
在这项研究中，我们在转录组（mRNA-seq）和挥发物混合水平上对比了抗虫性 Mp708 基因型和易感性 Tx601 基因型的防御反应。我们的结果表明，与 Tx601 植株相比，Mp708 植株在受到 CLA 侵害时，转录组重塑的程度更大。这些转录组特征表明，激素途径被激活，并以组成型和诱导型方式调节倍半萜和萜烯合酶。转录组分析还表明，在受到蚜虫侵害之前和之后，抗性 Mp708 基因型对乙烯和茉莉酸途径的调节具有明显的差异。最后，我们的结果还强调了在 Mp708 和 Tx601 植株中组成型产生挥发性有机化合物（VOCs）的重要性，这可能有助于玉米的直接和/或间接防御反应。
本研究进一步了解了防御信号网络在 Mp708 抗 CLA 中的作用。
