Dissecting Contrasts in Cell Death, Hormone, and Defense Signaling in Response to and Reactive Oxygen Species.

Plants require interaction between signaling pathways to differentiate and integrate stress responses and deploy appropriate defenses. The hormones ethylene, salicylic acid (SA), and jasmonic acid (JA) are important regulators of plant defenses. Numerous interactions between these signaling pathways are the cornerstone of robust plant immunity. Additionally, during the early response to pathogens, reactive oxygen species (ROS) act as signaling molecules. Here, we examined the extent of signal interaction in the early stages of infection. To enable a comparison between infection with ROS signaling, we subjected plants to ozone treatment, which stimulates an apoplastic ROS burst. We used a collection of single, double, and triple signaling mutants defective in hormone signaling and biosynthesis and subjected them to infection and ozone treatment at different timepoints. We examined lesion size, cell death, and gene expression (both quantitatively and spatially). The two treatments shared many similarities, especially in JA-insensitive mutants, which were sensitive to both treatments. Unexpectedly, a -susceptible JA-insensitive mutant (), became tolerant when both SA biosynthesis and signaling was impaired (), demonstrating that JA responses may be under the control of SA. Extensive marker gene analysis indicated JA as the main regulator of both and ozone defenses. In addition, we identified the transcription factor SR1 as a crucial regulator of expression and cell-death regulation, which contributes to resistance to . . Overall, our work further defines the context of ROS in plant defense signaling.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.