In this Research Topic, a collection of high-quality papers represents advances in our understanding of synthesis, biological functions and signaling activities of volatile and non-volatile plant oxylipins. Oxylipins are a large group of functionally and structurally diverse molecules produced from oxidized lipids and are widely known to have various roles in plant growth, development and interactions with biotic and abiotic stressors. Here we introduce 10 original research papers and two review papers on plant-environment, plant-pathogen, and plant-plant interactions. In this editorial piece, we overview the oxylipin metabolic pathways and introduce each research contribution in accordance with the corresponding metabolic pathway branches depicted in Figure 1. Jasmonates (JAs) are the best-studied group of plant oxylipins and are widely known as defense phytohormones. JA biosynthesis is triggered by the reaction of 13-lipoxygenase (13-LOX) on polyunsaturated fatty acids, which are abundant in plant membrane lipids, to produce 13-hydroperoxides (Figure 1). 13-Hydroperoxides are catalyzed by 13-allene oxide synthase (13-AOS), a member of the CYP74 family, and subsequently converted into 12-oxo-phytodienoic acid (OPDA) and JA by the sequential reactions of allene oxide cyclase, OPDA reductase, and β-oxidation processes (Acosta and Farmer, 2010). The major bioactive JA in vascular plants is the JA-Isoleucine conjugate (JA-Ile), which is recognized by the COI1 receptor complex (Yan et al., 2013). The JA signal activates a group of downstream transcription factors responsible for the transcriptional upregulation of defense genes (Yan et al., 2013). One of the common defense responses in plants is the activation of secondary metabolite accumulation, such as alkaloids and terpenoids, which act as toxic compounds to pathogens and pests (Ding et al., 2021). Many drugs used in modern medicine are derived from such plant secondary metabolites. For example, Catharanthus roseus is known to produce the anticancer alkaloids vinblastine and vincristine, belonging to the class of monoterpenoid indole alkaloids. Colinas et al. combined newly generated and publicly available transcriptome data of Catharanthus roseus to identify new members of the BIS and ORCA transcription factors that specifically regulate genes involved in the synthesis of these alkaloids.

Although JA signaling strongly induces defense responses, such activation is tightly controlled not to impede plant growth while defending (Guo et al., 2018). To prevent excessive induction of the defense, the active form of JA is rapidly converted to the inactive forms through hydroxylation and/or other metabolic processes (Koo et al., 2011). Kimberlin et al. report novel translational regulation of proper JA responses through the analysis of an Arabidopsis double mutant of cytochrome P450s, CYP94B1 and CYP94B3, which convert active JA-Ile to 12OH-JA-Ile. Bioactive