Salicylic acid positively regulates maize defenses against lepidopteran insects.

In response to insect attack, plants use intricate signaling pathways, including phytohormones, such as jasmonate (JA), ethylene (ET), and salicylic acid (SA), to activate defenses. Maize () is one of the most important staple food crops around the world. Previous studies have shown that the JA and ET signaling play important roles in maize defense against insects, but little is known about whether and how SA regulates maize resistance to insect herbivores. In this study, we ectopically expressed the () gene in maize plants ( maize) to block the accumulation of SA. It was found that compared with the wild-type (WT) maize, the maize exhibited decreased resistance to the generalist insects and and the specialist , and the compromised resistance in the maize was associated with decreased levels of defensive metabolites benzoxazinoids (Bxs) and chlorogenic acid (CA). Quantification of simulated feeding-induced JA, JA-isoleucine conjugate (JA-Ile), and ET in the WT and maize indicated that SA does not regulate JA or JA-Ile, but positively controls ET. We provide evidence suggesting that the SA pathway does not crosstalk with the JA or the ET signaling in regulating the accumulation of Bxs and CA. Transcriptome analysis revealed that the bHLH, ERF, and WRKY transcription factors might be involved in SA-regulated defenses. This study uncovers a novel and important phytohormone pathway in maize defense against lepidopterous larvae.