L-Glutamic acid negatively regulates extracellular ATP-induced reactive oxygen species signaling

Extracellular ATP (eATP) and L-Glutamic acid (L-Glu) are important damage associated molecular pattern (DAMP) molecules released from cells during injury. Both molecules trigger wound-associated signal transduction pathways, as well as the enhanced production of reactive oxygen species (ROS) by the RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) protein. However, whether eATP and L-Glu trigger overlapping or distinct pathways is mostly unknown. Here we report that Arabidopsis (Arabidopsis thaliana) responses to eATP or L-Glu are distinct from each other in terms of tissue specificity and transcriptomic responses. Thus, although both DAMPs trigger the expression of multiple wounding and hormone response transcripts in systemic tissues, eATP and L-Glu induced transcripts have little overlap between them. We further show that wounding of different tissues may result in ROS responses that are controlled by different DAMP receptors. Thus, activation of ROS production following injury of non-vascular tissues primarily depended on the eATP receptors PURINORECEPTOR 2 KINASE 1 and 2 (P2K1P2K2), while activation of ROS responses in vascular tissues following injury primarily depended on the L-Glu receptors GLU-LIKE RECEPTORS 3.3 and 3.6 (GLR3.3GLR3.6). Interestingly, we found that in the absence of the GLR3.3GLR3.6 receptors (i.e., in the glr3.3glr3.6 double mutant), the ROS response to eATP application is enhanced. This finding suggests that the L-Glu pathway may suppress the eATP pathway during wounding. Taken together, our findings suggest that the DAMP molecules eATP and L-Glu have complex interactions that appear to be both partly complementary and partly antagonistic, as well as tissue dependent.