Caleosin/peroxygenases (CLO/PXGs) play critical functional roles during plant development, oxylipin metabolism, and the response to abiotic/biotic stressors and environmental toxins. In Oryza sativa, peroxygenase-9 (OsPXG9) catabolizes intermediates in oxylipin biosynthesis produced by lipoxygenase-9 (9-LOX) and scavenges HOOH and CuOOH by transferring oxygen to hydroxy fatty acids (HFAs) but not to the free fatty acids. The resulting epoxide derivatives of HFAs are then enzymatically or non-enzymatically hydrolyzed into the corresponding trihydroxy derivatives. Results presented here demonstrate OsPXG9′s specificity for catabolizing products of the 9-LOX (and not for the 13-LOX) pathway of oxylipin biosynthesis. Overexpression of OsPXG9 reduces ROS (reactive oxygen species) abundance and reduces drought- and salt-stress-induced apoptotic cell death. The high expression level of OsPXG9 also stimulates drought- and salt-induced but not basal expression of antioxidant enzymes/pathways in plants, thereby increasing cellular resistance to drought. These results suggest that OsPXG9 decreases ROS abundance and is essential to increase resilience in rice plants exposed to exogenous or endogenous abiotic stress.

Caleosin/peroxygenases (CLO/PXGs) play critical functional roles during plant development, oxylipin metabolism and the response to abiotic/biotic stressors and environmental toxins. In Oryza sativa, peroxygenase 9 (OsPXG9) catabolizes intermediates in oxylipin biosynthesis produced by lipoxygenase 9 (9-LOX) and scavenges HOOH and CuOOH by transferring oxygen to hydroxy fatty acids (HFAs) but not to the free fatty acids. The resulting epoxide derivatives of HFAs are then enzymatically or non-enzymatically hydrolyzed into the corresponding trihydroxy derivatives. Results presented here demonstrate OsPXG9’s specificity for catabolizing products of the 9-LOX (and not for the 13-LOX) pathway of oxylipin biosynthesis. Overexpression of OsPXG9 reduces ROS abundance, reduces drought- and salt stress-induced apoptotic cell death and stimulates drought- and salt-induced but not basal expression of antioxidant enzymes/pathways in plants, thereby increasing cellular resistance to drought. These results suggest that OsPXG9 decreases ROS abundance and is essential to increase resilience in rice plants exposed to exogenous or endogenous abiotic stress.

Plant oxylipins are a diverse group of oxygenated fatty acid derivatives that function as important signaling molecules in plant responses to abiotic stress. Although jasmonates, particularly jasmonic acid (JA) and its derivatives, have been extensively studied, increasing evidence demonstrates that other oxylipin classes, including 12-oxophytodienoic acid (OPDA), green leaf volatiles (GLVs), reactive electrophilic oxylipins (RES), and peroxygenase (PXG)-derived oxylipins, also contribute to stress adaptation. This review summarizes current understanding of the molecular mechanisms underlying oxylipin signal perception, transduction, and regulation, with particular emphasis on interactions with other plant hormone pathways, reactive oxygen species (ROS), Calcium (Ca²⁺), and mitogen-activated protein kinase (MAPK) signaling. We further examine transcriptional, post-transcriptional, and post-translational mechanisms that regulate oxylipin responses and discuss their integration across individual and combined abiotic stresses. Particular attention is given to experimentally established mechanisms while distinguishing emerging or unresolved signaling processes. Understanding these interconnected signaling mechanisms will be important for developing strategies to improve crop resilience under global climate change.

Plant oxylipins are a diverse group of oxygenated fatty acid derivatives that function as important signaling molecules in plant responses to abiotic stress. Although jasmonates, particularly jasmonic acid (JA) and its derivatives, have been extensively studied, increasing evidence demonstrates that other oxylipin classes, including 12-oxophytodienoic acid (OPDA), green leaf volatiles (GLVs), reactive electrophilic oxylipins (RES), and peroxygenase (PXG)-derived oxylipins, also contribute to stress adaptation. This review summarizes current understanding of the molecular mechanisms underlying oxylipin signal perception, transduction, and regulation, with particular emphasis on interactions with other plant hormone pathways, reactive oxygen species (ROS), calcium (Ca²⁺), and mitogen-activated protein kinase (MAPK) signaling. We further examine transcriptional, post-transcriptional, and post-translational mechanisms that regulate oxylipin responses and discuss their integration across individual and combined abiotic stresses. Particular attention is given to experimentally established mechanisms while distinguishing emerging or unresolved signaling processes. Understanding these interconnected signaling mechanisms will be important for developing strategies to improve crop resilience under global climate change.