Phosphatidic acid is involved in regulation of autophagy in neurons in vitro and in vivo.

Major depressive disorder (MDD) is a common and severe psychiatric disease, which does not only lead to variety of neuropsychiatric symptoms, but unfortunately in a relatively large proportion of cases also to suicide. The pathogenesis of MDD still requires definition. We have previously shown that ceramide is increased in the blood plasma of patients with MDD. In mouse models of MDD, which are induced by treatment with corticosterone or application of chronic unpredictable stress, increased blood plasma ceramide also increased and caused an inhibition of phospholipase D in endothelial cells of the hippocampus and reduced phosphatidic acid levels in the hippocampus. Here, we demonstrated that corticosterone treatment of PC12 cells resulted in reduced cellular autophagy, which is corrected by treatment with phosphatidic acid. In vivo, treatment of mice with corticosterone or chronic unpredictable stress also reduced autophagy in hippocampus neurons. Autophagy was normalized upon i.v. injection of phosphatidic acid in these mouse models of MDD. In an attempt to identify targets of phosphatidic acid in neurons, we demonstrated that corticosterone reduced levels of the ganglioside GM1 in PC-12 cells and the hippocampus of mice, which were normalized by treatment of cells or i.v. injection of mice with phosphatidic acid. GM1 application also normalized autophagy in cultured neurons. Phosphatidic acid and GM1 corrected stress-induced alterations in behavior, i.e., mainly anxiety and anhedonia, in experimental MDD in mice. Our data suggest that phosphatidic acid may regulate via GM1 autophagy in neurons.

Upstream and downstream pathways of diacylglycerol kinase : Novel phosphatidylinositol turnover-independent signal transduction pathways.

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA). Mammalian DGK comprise ten isozymes (α-κ) that regulate a wide variety of physiological and pathological events. Recently, we revealed that DGK isozymes use saturated fatty acid (SFA)/monosaturated fatty acid (MUFA)-containing and docosahexaenoic acid (22:6)-containing DG species, but not phosphatidylinositol (PI) turnover-derived 18:0/20:4-DG. For example, DGKδ, which is involved in the pathogenesis of type 2 diabetes, preferentially uses SFA/MUFA-containing DG species, such as 16:0/16:0- and 16:0/18:1-DG species, in high glucose-stimulated skeletal muscle cells. Moreover, DGKδ, which destabilizes the serotonin transporter (SERT) and regulates the serotonergic system in the brain, primarily generates 18:0/22:6-PA. Furthermore, 16:0/16:0-PA is produced by DGKζ in Neuro-2a cells during neuronal differentiation. We searched for SFA/MUFA-PA- and 18:0/22:6-PA-selective binding proteins (candidate downstream targets of DGKδ) and found that SFA/MUFA-PA binds to and activates the creatine kinase muscle type, an energy-metabolizing enzyme, and that 18:0/22:6-PA interacts with and activates Praja-1, an E3 ubiquitin ligase acting on SERT, and synaptojanin-1, a key player in the synaptic vesicle cycle. Next, we searched for SFA/MUFA-DG-generating enzymes upstream of DGKδ. We found that sphingomyelin synthase (SMS)1, SMS2, and SMS-related protein (SMSr) commonly act as phosphatidylcholine (PC)-phospholipase C (PLC) and phosphatidylethanolamine (PE)-PLC, generating SFA/MUFA-DG species, in addition to SMS and ceramide phosphoethanolamine synthase. Moreover, the orphan phosphatase PHOSPHO1 showed PC- and PE-PLC activities that produced SFA/MUFA-DG. Although PC- and PE-PLC activities were first described 70-35 years ago, their proteins and genes were not identified for a long time. We found that DGKδ interacts with SMSr and PHOSPHO1, and that DGKζ binds to SMS1 and SMSr. Taken together, these results strongly suggest that there are previously unrecognized signal transduction pathways that include DGK isozymes and generate and utilize SFA/MUFA-DG/PA or 18:0/22:6-DG/PA but not PI-turnover-derived 18:0/20:4-DG/PA.

Expanding functions of the phosphatidylinositol/phosphatidate lipid transporter, PITPNC1 in physiology and in pathology.

PITPNC1 was the last of the PITPs to be identified and has been characterized as a binding protein for phosphatidylinositol and phosphatidate. In mammals, PITPNC1 is expressed as two splice variants whilst in zebrafish is expressed from two separate genes. The two splice variants have different expression profiles with the long splice variant having a prominent role in the brain. Several physiological functions have been identified including neuronal and metabolic functions. PITPNC1 also plays a significant role in cancer and has been identified as a risk factor in type 2 diabetes. Here, we review our current understanding of PITPNC1 in cell physiology and pathology.

Molecular determinants of phospholipid treatment to reduce intracellular cholesterol accumulation in NPC1 deficiency.

Niemann-Pick type C (NPC) disease, caused by mutations in the NPC1 or NPC2 genes, leads to abnormal intracellular cholesterol accumulation in late endosomes/lysosomes (LE/LY). Exogenous enrichment with lysobisphosphatidic acid (LBPA), also known as bis-monoacylglycerol phosphate or BMP, either directly or via the LBPA precursor phosphatidylglycerol (PG), has been investigated as a therapeutic intervention to reduce cholesterol accumulation in NPC disease. Here we report the effects of stereoisomer configuration and acyl chain composition of LBPA on cholesterol clearance in NPC1-deficient cells. We find that S,R, S,S, and S,R LBPA stereoisomers behaved similarly, with all 3 compounds leading to comparable reductions in filipin staining in two NPC1-deficient human fibroblast cell lines. Examination of several LBPA molecular species containing one or two mono- or polyunsaturated acyl chains showed that all LBPA species containing one 18:1 chain significantly reduced cholesterol accumulation, whereas the shorter chain species di-14:0 LBPA had little effect on cholesterol clearance in NPC1 deficient cells. Since cholesterol accumulation in NPC1 deficient cells can also be cleared by PG incubation, we used non-hydrolyzable PG analogues to determine whether conversion to LBPA is required for sterol clearance, or whether PG itself is effective. The results showed that non-hydrolyzable PG species were not appreciably converted to LBPA and showed virtually no cholesterol clearance efficacy in NPC1 deficient cells, supporting the notion that LBPA is the active agent promoting LE/LY cholesterol clearance. Overall these studies are helping to define the molecular requirements for potential therapeutic use of LBPA as an option for addressing NPC disease.

m6Am Methyltransferase PCIF1 Promotes LPP3 Mediated Phosphatidic Acid Metabolism and Renal Cell Carcinoma Progression.

N6-methyl-2'-O-methyladenosine (m6Am), occurring adjacent to the 7-methylguanosine (m7G) cap structure and catalyzed by the newly identified writer PCIF1 (phosphorylated CTD interacting factor 1), has been implicated in the pathogenesis of various diseases. However, its involvement in renal cell carcinoma (RCC) remains unexplored. Here, significant upregulation of PCIF1 and m6Am levels in RCC tissues are identified, unveiling their oncogenic roles both in vitro and in vivo. Mechanically, employing m6Am-Exo-Seq, LPP3 (phospholipid phosphatase 3) mRNA is identified as a key downstream target whose translation is enhanced by m6Am modification. Furthermore, LPP3 is revealed as a key regulator of phosphatidic acid metabolism, critical for preventing its accumulation in mitochondria and facilitating mitochondrial fission. Consequently, Inhibition of the PCIF1/LPP3 axis significantly altered mitochondrial morphology and reduced RCC tumor progression. In addition, depletion of PCIF1 sensitizes RCC to sunitinib treatment. This study highlights the intricate interplay between m6Am modification, phosphatidic acid metabolism, and mitochondrial dynamics, offering a promising therapeutic avenue for RCC.

Plastid LPAT1 is an integral inner envelope membrane protein with the acyltransferase domain located in the stroma.

KEY MESSAGE: The N-terminal transmembrane domain of LPAT1 crosses the inner membrane placing the N terminus in the intermembrane space and the C-terminal enzymatic domain in the stroma. Galactolipids mono- and di-galactosyl diacylglycerol are the major and vital lipids of photosynthetic membranes. They are synthesized by five enzymes hosted at different sub-chloroplast locations. However, localization and topology of the second-acting enzyme, lysophosphatidic acid acyltransferase 1 (LPAT1), which acylates the sn-2 position of glycerol-3-phosphate (G3P) to produce phosphatidic acid (PA), remain unclear. It is not known whether LPAT1 is located at the outer or the inner envelope membrane and whether its enzymatic domain faces the cytosol, the intermembrane space, or the stroma. Even the size of mature LPAT1 in chloroplasts is not known. More information is essential for understanding the pathways of metabolite flow and for future engineering endeavors to modify glycerolipid biosynthesis. We used LPAT1 preproteins translated in vitro for import assays to determine the precise size of the mature protein and found that the LPAT1 transit peptide is at least 85 residues in length, substantially longer than previously predicted. A construct comprising LPAT1 fused to the Venus fluorescent protein and driven by the LPAT1 promoter was used to complement an Arabidopsis lpat1 knockout mutant. To determine the sub-chloroplast location and topology of LPAT1, we performed protease treatment and alkaline extraction using chloroplasts containing in vitro-imported LPAT1 and chloroplasts isolated from LPAT1-Venus-complemented transgenic plants. We show that LPAT1 traverses the inner membrane via an N-terminal transmembrane domain, with its N terminus protruding into the intermembrane space and the C-terminal enzymatic domain residing in the stroma, hence displaying a different membrane topology from its bacterial homolog, PlsC.

PlsX and PlsY: Additional roles beyond glycerophospholipid synthesis in Gram-negative bacteria.

The unique asymmetry of the Gram-negative outer membrane, with glycerophospholipids (GPLs) in the inner leaflet and lipopolysaccharide (LPS) in the outer leaflet, works to resist external stressors and prevent the entry of toxic compounds. Thus, GPL and LPS synthesis must be tightly controlled to maintain the integrity of this essential structure. We sought to decipher why organisms like Escherichia coli possess two redundant pathways-PlsB and PlsX/Y-for synthesis of the GPL precursor lysophosphatidic acid (LPA). LPA is then converted by PlsC to the universal precursor for GPL synthesis, phosphatidic acid (PA). PlsB and PlsC are essential in E. coli, indicating they serve as the major pathway for PA synthesis. While loss of PlsX or PlsY individually has little consequence on the cell, the absence of both was lethal. To understand the synthetic lethality of this seemingly redundant PlsX/Y pathway, we performed a suppressor screen. Suppressor analysis indicated that ∆plsXY requires increased levels of glycerol-3-phosphate (G3P), a GPL precursor. In agreement, ∆plsXY required supplementation with G3P for survival. Furthermore, loss of PlsX dysregulated fatty acid synthesis, resulting in increased long-chain fatty acids. We show that although PlsX/Y together contribute to PA synthesis, they also contribute to the regulation of overall membrane biogenesis. Thus, synthetic lethality of ∆plsXY is multifactorial, suggesting that PlsX/Y has been maintained as a redundant system to fine-tune the synthesis of major lipids and promote cell envelope homeostasis.IMPORTANCEGram-negative bacteria must maintain optimal ratios of glycerophospholipids and lipopolysaccharide within the cell envelope for viability. Maintenance of proper outer membrane asymmetry allows for resistance to toxins and antibiotics. Here, we describe additional roles of PlsX and PlsY in Escherichia coli beyond lysophosphatidic acid synthesis, a key precursor of all glycerophospholipids. These findings suggest that PlsX and PlsY also play a larger role in impacting homeostasis of lipid synthesis.

Mycorrhizal and non-mycorrhizal perennial ryegrass roots exhibit differential regulation of lipid and Ca2+ signaling pathways in response to low and high temperature stresses.

Lipids and Ca2+ are involved as intermediate messengers in temperature-sensing signaling pathways. Arbuscular mycorrhizal (AM) symbiosis is a mutualistic symbiosis between fungi and terrestrial plants that helps host plants cope with adverse environmental conditions. Nonetheless, the regulatory mechanisms of lipid- and Ca2+-mediated signaling pathways in mycorrhizal plants under cold and heat stress have not been determined. The present work focused on investigating the lipid- and Ca2+-mediated signaling pathways in arbuscular mycorrhizal (AM) and non-mycorrhizal (NM) roots under temperature stress and determining the role of Ca2+ levels in AM symbiosis and temperature stress tolerance in perennial ryegrass (Lolium perenne L.) Compared with NM plants, AM symbiosis increased phosphatidic acid (PA) and Ca2+ signaling in the roots of perennial ryegrass, increasing the expression of genes associated with low temperature (LT) stress, including LpICE1, LpCBF3, LpCOR27, LpCOR47, LpIRI, and LpAFP, and high temperature (HT) stress, including LpHSFC1b, LpHSFC2b, LpsHSP17.8, LpHSP22, LpHSP70, and LpHSP90, under LT and HT conditions. These effects result in modulated antioxidant enzyme activities, reduced lipid peroxidation, and suppressed growth inhibition caused by LT and HT stresses. Furthermore, exogenous Ca2+ application enhanced AM symbiosis, leading to the upregulation of Ca2+ signaling pathway genes in roots and ultimately promoting the growth of perennial ryegrass under LT and HT stresses. These findings shed light on lipid and Ca2+ signal transduction in AM-associated plants under LT and HT stresses, emphasizing that Ca2+ enhances cold and heat tolerance in mycorrhizal plants.

High-level extracellular expression of phospholipase D by combinatorial fine-tuning strategy in Bacillus subtilis for efficient biosynthesis of phosphatidic acid.

Although Bacillus subtilis shows promise as a potential microbial cell factory for phospholipase D (PLD) expression, its production capacity remains insufficient. In this study, a secretory expression system, by co-optimization the promoter and signal peptides and employing a fed-batch fermentation strategy, was constructed to enhance expression of PLD from separate sources. The highest PLD production of 4056.9 U/mL was observed using this system, with a PLD production efficiency of 52.0 U/mL/h. Finally, a phosphatidic acid (PA) biosynthesis system was established using the constructed PLD as a catalyst, which achieved a PA yield of 219.1 g/L. This is the highest PLD production and PA yield reported globally to date. The protocol has significant potential for application for industrial PLD production as well as enzymatic phospholipids modification and also provides a valuable reference for overexpressing proteins in B. subtilis.

Architecture and function of yeast phosphatidate phosphatase Pah1 domains/regions.

Phosphatidate (PA) phosphatase, which catalyzes the Mg2+-dependent dephosphorylation of PA to produce diacylglycerol, provides a direct precursor for the synthesis of the storage lipid triacylglycerol and the membrane phospholipids phosphatidylcholine and phosphatidylethanolamine. The enzyme controlling the key phospholipid PA also plays a crucial role in diverse aspects of lipid metabolism and cell physiology. PA phosphatase is a peripheral membrane enzyme that is composed of multiple domains/regions required for its catalytic function and subcellular localization. In this review, we discuss the domains/regions of PA phosphatase from the yeast Saccharomyces cerevisiae with reference to the homologous enzyme from mammalian cells.

Optogenetic Strategies for Optimizing the Performance of Phospholipids Biosensors.

High-performance biosensors play a crucial role in elucidating the intricate spatiotemporal regulatory roles and dynamics of membrane phospholipids. However, enhancing the sensitivity and imaging performance remains a significant challenge. Here, optogenetic-based strategies are presented to optimize phospholipid biosensors. These strategies involves presequestering unbound biosensors in the cell nucleus and regulating their cytosolic levels with blue light to minimize background signal interference in phospholipid detection, particularly under conditions of high expression levels of biosensor. Furthermore, optically controlled phase separation and the SunTag system are employed to generate punctate probes for substrate detection, thereby amplifying biosensor signals and enhancing visualization of the detection process. These improved phospholipid biosensors hold great potential for enhancing the understanding of the spatiotemporal dynamics and regulatory roles of membrane lipids in live cells and the methodological insights in this study might be valuable for developing other high-performance biosensors.

Revisiting the role of phospholipases in alzheimer's: crosstalk with processed food.

Phospholipases such as phospholipase-A, phospholipase-B, phospholipase-C and phospholipase-D are important functional enzymes of the cell membrane responsible for a variety of functions such as signal transduction, production of lipid mediators, metabolite digestion and playing a pathological role in central nervous system diseases. Phospholipases have shown an association with Alzheimer's disease and these enzymes have found a correlation with several metabolic pathways that can lead to the activation of inflammatory signals via astrocytes and microglial cells. We also highlighted unhealthy practices like smoking and consuming processed foods, rich in nitroso compounds and phosphatidic acid, which contribute to neuronal damage in AD through phospholipases. A few therapeutic approaches such as the use of inhibitors of phospholipase-D,phospholipase A2 as well as autophagy-mediated inhibition have been discussed to control the onset of AD. This paper serves as a crosstalk between phospholipases and their role in neurodegenerative pathways as well as their influence on other biomolecules of lipid membranes, which are acquired through unhealthy diets and possible methods to treat these anomalies occurring due to their metabolic disorder involving phospholipases acting as major signaling molecules.

Ammonium bicarbonate buffers combined with hybrid surface technology columns improve the peak shape of strongly tailing lipids.

BACKGROUND: Lipids such as phosphatidic acids (PAs) and cardiolipins (CLs) present strongly tailing peaks in reversed phase liquid chromatography, which entails low detectability. They are usually analyzed by hydrophilic interaction liquid chromatography (HILIC), which hampers high-throughput lipidomics. Thus, there is a great need for improved analytical methods in order to obtain a broader coverage of the lipidome in a single chromatographic method. We investigated the effect of ammonium bicarbonate (ABC) on peak asymmetry and detectability, in comparison with ammonium formate (AFO) on both a conventional BEH C18 column and an HST-CSH C18 column. RESULTS: The combination of 2.5 mM ABC buffer pH 8 with an HST-CSH C18 column produced significantly improved results, reducing the asymmetry factor at 10 % peak height of PA 16:0/18:1 from 8.4 to 1.6. Furthermore, on average, there was up to a 54-fold enhancement in the peak height of its [M - H]- ion compared to AFO and the BEH C18 column. We confirmed this beneficial effect on other strongly tailing lipids, with accessible phosphate moieties e.g., cardiolipins, phosphatidylinositol phosphate, phosphatidylinositol bisphosphate, phosphorylated ceramide and phosphorylated sphingosine. Furthermore, we found an increased detectability of phospho- and sphingolipids up to 28 times in negative mode when using an HST-CSH C18 column. The method was successfully applied to mouse liver samples, where previously undetected endogenous phospholipids could be analyzed with improved chromatographic separation. SIGNIFICANCE: In conclusion, the use of 2.5 mM ABC substantially improved the peak shape of PAs and enhanced the detectability of the lipidome in negative mode on an RPLC-ESI-Q-TOF-MS system on both BEH C18 and HST-CSH C18 columns. This method provides a wider coverage of the lipidome with one single injection for future lipidomic applications in negative mode.

Synthesis of Azo Analogs for Investigating Phosphatidic Acid-Mediated Signaling.

Phosphatidic acid (PA) is a key signaling lipid that plays a crucial role in regulating various cellular processes. Studies have shown that azobenzene-containing PA analogues can be used as an all-chemical strategy for light-mediated control of PA signaling. These photoswitchable lipids offer a solution to the limitations of traditional bulk dosing methods by allowing for light- and shape-dependent interactions with protein effectors and lipid-metabolizing enzymes. This chapter describes how to synthesize AzoPA and dAzoPA.

Exploring lipin1 as a promising therapeutic target for the treatment of Duchenne muscular dystrophy.

BACKGROUND: Duchenne muscular dystrophy (DMD) is a progressive and devastating muscle disease, resulting from the absence of dystrophin. This leads to cell membrane instability, susceptibility to contraction-induced muscle damage, subsequent muscle degeneration, and eventually disability and early death of patients. Currently, there is no cure for DMD. Our recent studies identified that lipin1 plays a critical role in maintaining myofiber stability and integrity. However, lipin1 gene expression levels are dramatically reduced in the skeletal muscles of DMD patients and mdx mice. METHODS: To identify whether increased lipin1 expression could prevent dystrophic pathology, we employed unique muscle-specific mdx:lipin1 transgenic (mdx:lipin1Tg/0) mice in which lipin1 was restored in the dystrophic muscle of mdx mice, intramuscular gene delivery, as well as cell culture system. RESULTS: We found that increased lipin1 expression suppressed muscle degeneration and inflammation, reduced fibrosis, strengthened membrane integrity, and resulted in improved muscle contractile and lengthening force, and muscle performance in mdx:lipin1Tg/0 compared to mdx mice. To confirm the role of lipin1 in dystrophic muscle, we then administered AAV1-lipin1 via intramuscular injection in mdx mice. Consistently, lipin1 restoration inhibited myofiber necroptosis and lessened muscle degeneration. Using a cell culture system, we further found that differentiated primary mdx myoblasts had elevated expression levels of necroptotic markers and medium creatine kinase (CK), which could be a result of sarcolemmal damage. Most importantly, increased lipin1 expression levels in differentiated myoblasts from mdx:lipin1Tg/0 mice substantially inhibited the elevation of necroptotic markers and medium CK levels. CONCLUSIONS: Overall, our data suggest that lipin1 is a promising therapeutic target for the treatment of dystrophic muscles.

Phospholipid Signaling in Crop Plants: A Field to Explore.

In plant models such as Arabidopsis thaliana, phosphatidic acid (PA), a key molecule of lipid signaling, was shown not only to be involved in stress responses, but also in plant development and nutrition. In this article, we highlight lipid signaling existing in crop species. Based on open access databases, we update the list of sequences encoding phospholipases D, phosphoinositide-dependent phospholipases C, and diacylglycerol-kinases, enzymes that lead to the production of PA. We show that structural features of these enzymes from model plants are conserved in equivalent proteins from selected crop species. We then present an in-depth discussion of the structural characteristics of these proteins before focusing on PA binding proteins. For the purpose of this article, we consider RESPIRATORY BURST OXIDASE HOMOLOGUEs (RBOHs), the most documented PA target proteins. Finally, we present pioneering experiments that show, by different approaches such as monitoring of gene expression, use of pharmacological agents, ectopic over-expression of genes, and the creation of silenced mutants, that lipid signaling plays major roles in crop species. Finally, we present major open questions that require attention since we have only a perception of the peak of the iceberg when it comes to the exciting field of phospholipid signaling in plants.

CDP-DAG synthesis by peripheral membrane-bound Tam41-type enzymes.

Cytidine diphosphate diacylglycerol (CDP-DAG) is a critical intermediate that is converted to multiple phospholipids in prokaryotes and eukaryotes. In budding yeast, CDP-DAG synthesis from cytidine triphosphate (CTP) and phosphatidic acid (PA) is catalyzed by the membrane-integrated protein Cds1 in the endoplasmic reticulum and the peripheral membrane-bound protein Tam41 in mitochondria. Although a recent study revealed that the fission yeast SpTam41 consists of a nucleotidyltransferase domain and a winged helix domain, forming an active-site pocket for CTP binding between the two domains together with a C-terminal amphipathic helix for membrane association, how CTP and Mg 2+, a most-favoured divalent cation, are accommodated with PA remains obscure. A more recent report by Kimura et al. (J. Biochem. 2022; 171:429-441) solved the crystal structure of FbTam41, a functional ortholog from a Firmicutes bacterium, with CTP-Mg 2+, successfully providing a detailed molecular view of CDP-DAG synthesis. In this commentary, our current understanding of Tam41-mediated reaction is discussed.

Disordered region of nuclear membrane protein Bqt4 recruits phosphatidic acid to the nuclear envelope to maintain its structural integrity.

The nuclear envelope (NE) is a permeable barrier that maintains nuclear-cytoplasmic compartmentalization and ensures nuclear function; however, it ruptures in various situations such as mechanical stress and mitosis. Although the protein components for sealing a ruptured NE have been identified, the mechanism by which lipid components are involved in this process remains to be elucidated. Here, we found that an inner nuclear membrane (INM) protein Bqt4 directly interacts with phosphatidic acid (PA) and serves as a platform for NE maintenance in the fission yeast Schizosaccharomyces pombe. The intrinsically disordered region (IDR) of Bqt4, proximal to the transmembrane domain, binds to PA and forms a solid aggregate in vitro. Excessive accumulation of Bqt4 IDR in INM results in membrane overproliferation and lipid droplet formation in the nucleus, leading to centromere dissociation from the NE and chromosome missegregation. Our findings suggest that Bqt4 IDR controls nuclear membrane homeostasis by recruiting PA to the INM, thereby maintaining the structural integrity of the NE.

Fine-tuning phosphatidic acid production for optimal plant stress responses.

Phosphatidic acid (PA) is involved in biotic and abiotic stress responses in plants. Here, we summarize quantitative lipidomics and real-time imaging used in PA studies and highlight recent studies of diacylglycerol (DAG) kinase (DGK) 5, an enzyme involved in PA biosynthesis, facilitating fine-tuning PA production for optimal stress responses in plants.