Nonspecific phospholipase C4 hydrolyzes phosphosphingolipids and sustains plant root growth during phosphate deficiency.

Phosphate is a vital macronutrient for plant growth, and its availability in soil is critical for agricultural sustainability and productivity. A substantial amount of cellular phosphate is used to synthesize phospholipids for cell membranes. Here, we identify a key enzyme, nonspecific phospholipase C4 (NPC4) that is involved in phosphosphingolipid hydrolysis and remodeling in Arabidopsis during phosphate starvation. The level of glycosylinositolphosphorylceramide (GIPC), the most abundant sphingolipid in Arabidopsis thaliana, decreased upon phosphate starvation. NPC4 was highly induced by phosphate deficiency, and NPC4 knockouts in Arabidopsis decreased the loss of GIPC and impeded root growth during phosphate starvation. Enzymatic analysis showed that NPC4 hydrolyzed GIPC and displayed a higher activity toward GIPC as a substrate than toward the common glycerophospholipid phosphatidylcholine. NPC4 was associated with the plasma membrane lipid rafts in which GIPC is highly enriched. These results indicate that NPC4 uses GIPC as a substrate in planta and the NPC4-mediated sphingolipid remodeling plays a positive role in root growth in Arabidopsis response to phosphate deficiency.

Phospholipase Dα6 and phosphatidic acid regulate gibberellin signaling in rice.

Phospholipase D (PLD) hydrolyzes membrane lipids to produce phosphatidic acid (PA), a lipid mediator involved in various cellular and physiological processes. Here, we show that PLDα6 and PA regulate the distribution of GIBBERELLIN (GA)-INSENSITIVE DWARF1 (GID1), a soluble gibberellin receptor in rice. PLDα6-knockout (KO) plants display less sensitivity to GA than WT, and PA restores the mutant to a normal GA response. PA binds to GID1, as documented by liposome binding, fat immunoblotting, and surface plasmon resonance. Arginines 79 and 82 of GID1 are two key amino acid residues required for PA binding and also for GID1's nuclear localization. The loss of PLDα6 impedes GA-induced nuclear localization of GID1. In addition, PLDα6-KO plants attenuated GA-induced degradation of the DELLA protein SLENDER RICE1 (SLR1). These data suggest that PLDα6 and PA positively mediate GA signaling in rice via PA binding to GID1 and promotion of its nuclear translocation.

Glycerol-3-Phosphate Acyltransferase GPAT9 Enhanced Seed Oil Accumulation and Eukaryotic Galactolipid Synthesis in Brassica napus.

Glycerol-3-phosphate acyltransferase GPAT9 catalyzes the first acylation of glycerol-3-phosphate (G3P), a committed step of glycerolipid synthesis in Arabidopsis. The role of GPAT9 in Brassica napus remains to be elucidated. Here, we identified four orthologs of GPAT9 and found that BnaGPAT9 encoded by BnaC01T0014600WE is a predominant isoform and promotes seed oil accumulation and eukaryotic galactolipid synthesis in Brassica napus. BnaGPAT9 is highly expressed in developing seeds and is localized in the endoplasmic reticulum (ER). Ectopic expression of BnaGPAT9 in E. coli and siliques of Brassica napus enhanced phosphatidic acid (PA) production. Overexpression of BnaGPAT9 enhanced seed oil accumulation resulting from increased 18:2-fatty acid. Lipid profiling in developing seeds showed that overexpression of BnaGPAT9 led to decreased phosphatidylcholine (PC) and a corresponding increase in phosphatidylethanolamine (PE), implying that BnaGPAT9 promotes PC flux to storage triacylglycerol (TAG). Furthermore, overexpression of BnaGPAT9 also enhanced eukaryotic galactolipids including monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), with increased 36:6-MGDG and 36:6-DGDG, and decreased 34:6-MGDG in developing seeds. Collectively, these results suggest that ER-localized BnaGPAT9 promotes PA production, thereby enhancing seed oil accumulation and eukaryotic galactolipid biosynthesis in Brassica napus.

Non-specific phospholipase C4 hydrolyzes phosphosphingolipids and phosphoglycerolipids and promotes rapeseed growth and yield.

Phosphorus is a major nutrient vital for plant growth and development, with a substantial amount of cellular phosphorus being used for the biosynthesis of membrane phospholipids. Here, we report that NON-SPECIFIC PHOSPHOLIPASE C4 (NPC4) in rapeseed (Brassica napus) releases phosphate from phospholipids to promote growth and seed yield, as plants with altered NPC4 levels showed significant changes in seed production under different phosphate conditions. Clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated knockout of BnaNPC4 led to elevated accumulation of phospholipids and decreased growth, whereas overexpression (OE) of BnaNPC4 resulted in lower phospholipid contents and increased plant growth and seed production. We demonstrate that BnaNPC4 hydrolyzes phosphosphingolipids and phosphoglycerolipids in vitro, and plants with altered BnaNPC4 function displayed changes in their sphingolipid and glycerolipid contents in roots, with a greater change in glycerolipids than sphingolipids in leaves, particularly under phosphate deficiency conditions. In addition, BnaNPC4-OE plants led to the upregulation of genes involved in lipid metabolism, phosphate release, and phosphate transport and an increase in free inorganic phosphate in leaves. These results indicate that BnaNPC4 hydrolyzes phosphosphingolipids and phosphoglycerolipids in rapeseed to enhance phosphate release from membrane phospholipids and promote growth and seed production.

Acylation of non-specific phospholipase C4 determines its function in plant response to phosphate deficiency.

Non-specific phospholipase C (NPC) is involved in plant growth, development and stress responses. To elucidate the mechanism by which NPCs mediate cellular functions, here we show that NPC4 is S-acylated at the C terminus and that acylation determines its plasma membrane (PM) association and function. The acylation of NPC4 was detected using NPC4 isolated from Arabidopsis and reconstituted in vitro. The C-terminal Cys-533 was identified as the S-acylation residue, and the mutation of Cys-533 to Ala-533 in NPC4 (NPC4C533A ) led to the loss of S-acylation and membrane association of NPC4. The knockout of NPC4 impeded the phosphate deficiency-induced decrease of the phosphosphingolipid glycosyl inositol phosphoryl ceramide (GIPC), but introducing NPC4C533A to npc4-1 failed to complement this defect, thereby supporting the hypothesis that the non-acylated NPC4C533A fails to hydrolyze GIPC during phosphate deprivation. Moreover, NPC4C533A failed to complement the primary root growth in npc4-1 under stress. In addition, NPC4 in Brassica napus was S-acylated and mutation of the S-acylating cysteine residue of BnaC01.NPC4 led to the loss of S-acylation and its membrane association. Together, our results reveal that S-acylation of NPC4 in the C terminus is conserved and required for its membrane association, phosphosphingolipid hydrolysis and function in plant stress responses.

Dual Activities of Plant cGMP-Dependent Protein Kinase and Its Roles in Gibberellin Signaling and Salt Stress.

Cyclic GMP (cGMP) is an important regulator in eukaryotes, and cGMP-dependent protein kinase (PKG) plays a key role in perceiving cellular cGMP in diverse physiological processes in animals. However, the molecular identity, property, and function of PKG in plants remain elusive. In this study, we have identified PKG from plants and characterized its role in mediating the gibberellin (GA) response in rice (Oryza sativa). PKGs from plants are structurally unique with an additional type 2C protein phosphatase domain. Rice PKG possesses both protein kinase and phosphatase activities, and cGMP stimulates its kinase activity but inhibits its phosphatase activity. One of PKG's targets is GAMYB, a transcription factor in GA signaling, and the dual activities of PKG catalyze the reversible phosphorylation of GAMYB at Ser6 and modulate the nucleocytoplasmic distribution of GAMYB in response to GA. Loss of PKG impeded the nuclear localization of GAMYB and abolished GAMYB function in the GA response, leading to defects in GA-induced seed germination, internode elongation, and pollen viability. In addition to GAMYB, PKG has multiple potential targets and thus has broad effects, particularly in the salt stress response.

The Examination of the Role of Rice Lysophosphatidic Acid Acyltransferase 2 in Response to Salt and Drought Stresses.

Phosphatidic acid (PA) is an important signal molecule in various biological processes including osmotic stress. Lysophosphatidic acid acyltransferase (LPAT) acylates the sn-2 position of the glycerol backbone of lysophosphatidic acid (LPA) to produce PA. The role of LPAT2 and its PA in osmotic stress response remains elusive in plants. Here we showed that LPAT2-derived PA is important for salt and drought stress tolerance in rice. Rice LPAT2 was localized to the endoplasmic reticulum (ER) to catalyze the PA synthesis. The LPAT2 transcript was induced by osmotic stress such as high salinity and water deficit. To reveal its role in osmotic stress response, an LPAT2 knockdown mutant, designated lpat2, was isolated from rice, which contained a reduced PA level relative to wild type (WT) plants under salt stress and water deficit. The lpat2 mutant was more susceptible to osmotic stress and less sensitive to abscisic acid (ABA) than that of WT, which was recovered by either PA supplementation or genetic LPAT2 complementation. Moreover, suppressed LPAT2 also led to a large number of differentially expressed genes (DEGs) involved in diverse processes, particularly, in ABA response, kinase signaling, and ion homeostasis in response to salt stress. Together, LPAT2-produced PA plays a positive role in osmotic tolerance through mediating ABA response, which leads to transcriptional alteration of genes related to ABA response, protein kinase signaling, and ion homeostasis.

Plastid Glycerol-3-phosphate Acyltransferase Enhanced Plant Growth and Prokaryotic Glycerolipid Synthesis in Brassica napus.

Plastid-localized glycerol-3-phosphate acyltransferase (ATS1) catalyzes the first-step reaction in glycerolipid assembly through transferring an acyl moiety to glycerol-3-phosphate (G3P) to generate lysophosphatidic acid (LPA), an intermediate in lipid metabolism. The effect of ATS1 overexpression on glycerolipid metabolism and growth remained to be elucidated in plants, particularly oil crop plants. Here, we found that overexpression of BnATS1 from Brassica napus enhanced plant growth and prokaryotic glycerolipid biosynthesis. BnATS1 is localized in chloroplasts and an in vitro assay showed that BnATS1 had acylation activity toward glycerol 3-phosphate to produce LPA. Lipid profiling showed that overexpression of BnATS1 led to increases in multiple glycerolipids including phosphatidylglycerol (PG), monogalactosyldiacylglycerol (MGDG), phosphatidylcholine (PC), and phosphatidylinositol (PI), with increased polyunsaturated fatty acids. Moreover, increased MGDG was attributed to the elevation of 34:6- and 34:5-MGDG, which were derived from the prokaryotic pathway. These results suggest that BnATS1 promotes accumulation of polyunsaturated fatty acids in cellular membranes, thus enhances plant growth under low-temperature conditions in Brassica napus.

Cytidinediphosphate-diacylglycerol synthase 5 is required for phospholipid homeostasis and is negatively involved in hyperosmotic stress tolerance.

Cytidinediphosphate diacylglycerol synthase (CDS) uses phosphatidic acid (PA) and cytidinetriphosphate to produce cytidinediphosphate-diacylglycerol, an intermediate for phosphatidylglycerol (PG) and phosphatidylinositol (PI) synthesis. This study shows that CDS5, one of the five CDSs of the Oryza sativa (rice) genome, has multifaceted effects on plant growth and stress responses. The loss of CDS5 resulted in a decrease in PG and PI levels, defective thylakoid membranes, pale leaves in seedlings and growth retardation. In addition, the loss of CDS5 led to an elevated PA level and enhanced hyperosmotic tolerance. The inhibition of phospholipase D (PLD)-derived PA formation in cds5 restored the hyperosmotic stress tolerance of the mutant phenotype to that of the wild type, suggesting that CDS5 functions as a suppressor in PLD-derived PA signaling and negatively affects hyperosmotic stress tolerance.

Diacylglycerol kinase and associated lipid mediators modulate rice root architecture.

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA), and both DAG and PA are lipid mediators in the cell. Here we show that DGK1 in rice (Oryza sativa) plays important roles in root growth and development. Two independent OsDGK1-knockout (dgk1) lines exhibited a higher density of lateral roots (LRs) and thinner seminal roots (SRs), whereas OsDGK1-overexpressing plants displayed a lower LR density and thicker SRs than wild-type (WT) plants. Overexpression of OsDGK1 led to a decline in the DGK substrate DAG whereas specific PA species decreased in dgk1 roots. Supplementation of DAG to OsDGK1-overexpressing seedlings restored the LR density and SR thickness whereas application of PA to dgk1 seedlings restored the LR density and SR thickness to those of the WT. In addition, treatment of rice seedlings with the DGK inhibitor R59022 increased the level of DAG and decreased PA, which also restored the root phenotype of OsDGK1-overexpressing seedlings close to that of the WT. Together, these results indicate that DGK1 and associated lipid mediators modulate rice root architecture; DAG promotes LR formation and suppresses SR growth whereas PA suppresses LR number and promotes SR thickness.

Rice sulfoquinovosyltransferase SQD2.1 mediates flavonoid glycosylation and enhances tolerance to osmotic stress.

Sulfoquinovosyltransferase 2 (SQD2) catalyses the final step in the sulfoquinovosyldiacylglycerol (SQDG) biosynthetic pathway. It is involved in the phosphate starvation response. Here, we show that rice SQD2.1 has dual activities catalysing SQDG synthesis and flavonoid glycosylation. SQD2.1 null mutants (sqd2.1) in rice had decreased levels of glycosidic flavonoids, particularly apigenin 7-O-glucoside (A7G), whereas these metabolites were increased in rice plants overexpressing SQD2.1. The sqd2.1 mutants and SQD2.1 overexpressing lines showed reduced and enhanced, respectively, tolerance to salinity and drought. Treating the sqd2.1 mutants with A7G decreased oxidative damage and restored stress tolerance to the wild-type levels. These findings demonstrate that SQD2.1 has a novel function in the glycosylation of flavonoids that is required for osmotic stress tolerance in rice. The novel activity of SQD2.1 in the production of glycosidic flavonoids improves scavenging of reactive oxygen species and protects against excessive oxidation.

Phosphatidylinositol-hydrolyzing phospholipase C4 modulates rice response to salt and drought.

Phosphatidylinositol-specific phospholipase C (PI-PLC) is involved in stress signalling but its signalling function remains largely unknown in crop plants. Here, we report that the PI-PLC4 from rice (Oryza sativa cv), OsPLC4, plays a positive role in osmotic stress response. Two independent knockout mutants, plc4-1 and plc4-2, exhibited decreased seedling growth and survival rate whereas overexpression of OsPLC4 improved survival rate under high salinity and water deficiency, compared with wild type (WT). OsPLC4 hydrolyses PI, phosphatidylinositol 4-phosphate (PI4P), and phosphatidylinositol-4,5-bisphosphate (PIP2 ) to generate diacylglycerol (DAG) in vitro. Knockout of OsPLC4 attenuated salt-induced increase of phosphatidic acid (PA) whereas overexpression of OsPLC4 decreased the level of PI4P and PIP2 under salt treatment. Applications of DAG or PA restored the growth defect of plc4-1 to WT but DAG kinase inhibitor 1 blocked the complementary effect of DAG in plc4-1 under salt stress. In addition, the loss of OsPLC4 compromised the increase of inositol triphosphate and free cytoplasmic Ca2+ ([Ca2+ ]cyt ) and inhibited the induction of genes involved in Ca2+ sensor and osmotic stress response to salt stress. The results indicate that OsPLC4 modulates the activity of two signalling pathways, PA and Ca2+ , to affect rice seedling response to osmotic stress.

Overexpression of WAX INDUCER1/SHINE1 Gene Enhances Wax Accumulation under Osmotic Stress and Oil Synthesis in Brassica napus.

WAX INDUCER1/SHINE1 (WIN1) belongs to the AP2/EREBP transcription factor family and plays an important role in wax and cutin accumulation in plants. Here we show that BnWIN1 from Brassica napus (Bn) has dual functions in wax accumulation and oil synthesis. Overexpression (OE) of BnWIN1 led to enhanced wax accumulation and promoted growth without adverse effects on oil synthesis under salt stress conditions. Lipid profiling revealed that BnWIN1-OE plants accumulated more waxes with elevated C29-alkanes, C31-alkanes, C28-alcohol, and C29-alcohol relative to wild type (WT) under salt stress. Moreover, overexpression of BnWIN1 also increased seed oil content under normal growth conditions. BnWIN1 directly bound to the promoter region of genes encoding biotin carboxyl carrier protein 1 (BCCP1), glycerol-3-phosphate acyltransferase 9 (GPAT9), lysophosphatidic acid acyltransferase 5 (LPAT5), and diacylglycerol acyltransferase 2 (DGAT2) involved in the lipid anabolic process. Overexpression of BnWIN1 resulted in upregulated expression of numerous genes involved in de novo fatty acid synthesis, wax accumulation, and oil production. The results suggest that BnWIN1 is a transcriptional activator to regulate the biosynthesis of both extracellular and intracellular lipids.

Comparative Transcriptome Analysis of Developing Seeds and Silique Wall Reveals Dynamic Transcription Networks for Effective Oil Production in Brassica napus L.

Vegetable oil is an essential constituent of the human diet and renewable raw material for industrial applications. Enhancing oil production by increasing seed oil content in oil crops is the most viable, environmentally friendly, and sustainable approach to meet the continuous demand for the supply of vegetable oil globally. An in-depth understanding of the gene networks involved in oil biosynthesis during seed development is a prerequisite for breeding high-oil-content varieties. Rapeseed (Brassica napus) is one of the most important oil crops cultivated on multiple continents, contributing more than 15% of the world's edible oil supply. To understand the phasic nature of oil biosynthesis and the dynamic regulation of key pathways for effective oil accumulation in B. napus, comparative transcriptomic profiling was performed with developing seeds and silique wall (SW) tissues of two contrasting inbred lines with ~13% difference in seed oil content. Differentially expressed genes (DEGs) between high- and low-oil content lines were identified across six key developmental stages, and gene enrichment analysis revealed that genes related to photosynthesis, metabolism, carbohydrates, lipids, phytohormones, transporters, and triacylglycerol and fatty acid synthesis tended to be upregulated in the high-oil-content line. Differentially regulated DEG patterns were revealed for the control of metabolite and photosynthate production in SW and oil biosynthesis and accumulation in seeds. Quantitative assays of carbohydrates and hormones during seed development together with gene expression profiling of relevant pathways revealed their fundamental effects on effective oil accumulation. Our results thus provide insights into the molecular basis of high seed oil content (SOC) and a new direction for developing high-SOC rapeseed and other oil crops.

Ribosomal protein S6 kinase1 coordinates with TOR-Raptor2 to regulate thylakoid membrane biosynthesis in rice.

Ribosomal protein S6 kinase (S6K) functions as a key component in the target of rapamycin (TOR) pathway involved in multiple processes in eukaryotes. The role and regulation of TOR-S6K in lipid metabolism remained unknown in plants. Here we provide genetic and pharmacological evidence that TOR-Raptor2-S6K1 is important for thylakoid galactolipid biosynthesis and thylakoid grana modeling in rice (Oryza sativa L.). Genetic suppression of S6K1 caused pale yellow-green leaves, defective thylakoid grana architecture. S6K1 directly interacts with Raptor2, a core component in TOR signaling, and S6K1 activity is regulated by Raptor2 and TOR. Plants with suppressed Raptor2 expression or reduced TOR activity by inhibitors mimicked the S6K1-deficient phenotype. A significant reduction in galactolipid content was found in the s6k1, raptor2 mutant or TOR-inhibited plants, which was accompanied by decreased transcript levels of the set of genes such as lipid phosphate phosphatase α5 (LPPα5), MGDG synthase 1 (MGD1), and DGDG synthase 1 (DGD1) involved in galactolipid synthesis, compared to the control plants. Moreover, loss of LPPα5 exhibited a similar phenotype with pale yellow-green leaves. These results suggest that TOR-Raptor2-S6K1 is important for modulating thylakoid membrane lipid biosynthesis, homeostasis, thus enhancing thylakoid grana architecture and normal photosynthesis ability in rice.

Phospholipase Dε enhances Braasca napus growth and seed production in response to nitrogen availability.

Phospholipase D (PLD), which hydrolyses phospholipids to produce phosphatidic acid, has been implicated in plant response to macronutrient availability in Arabidopsis. This study investigated the effect of increased PLDε expression on nitrogen utilization in Brassica napus to explore the application of PLDε manipulation to crop improvement. In addition, changes in membrane lipid species in response to nitrogen availability were determined in the oil seed crop. Multiple PLDε over expression (PLDε-OE) lines displayed enhanced biomass accumulation under nitrogen-deficient and nitrogen-replete conditions. PLDε-OE plants in the field produced more seeds than wild-type plants but have no impact on seed oil content. Compared with wild-type plants, PLDε-OE plants were enhanced in nitrate transporter expression, uptake and reduction, whereas the activity of nitrite reductase was higher under nitrogen-depleted, but not at nitrogen-replete conditions. The level of nitrogen altered membrane glycerolipid metabolism, with greater impacts on young than mature leaves. The data indicate increased expression of PLDε has the potential to improve crop plant growth and production under nitrogen-depleted and nitrogen-replete conditions.

Patatin-related phospholipase A, pPLAIIIα, modulates the longitudinal growth of vegetative tissues and seeds in rice.

Patatin-related phospholipase A (pPLA) hydrolyses glycerolipids to produce fatty acids and lysoglycerolipids. The Oryza sativa genome has 21 putative pPLAs that are grouped into five subfamilies. Overexpression of OspPLAIIIα resulted in a dwarf phenotype with decreased length of rice stems, roots, leaves, seeds, panicles, and seeds, whereas OspPLAIIIα-knockout plants had longer panicles and seeds. OspPLAIIIα-overexpressing plants were less sensitive than wild-type and knockout plants to gibberellin-promoted seedling elongation. OspPLAIIIα overexpression and knockout had an opposite effect on the expression of the growth repressor SLENDER1 in the gibberellin signalling process. OspPLAIIIα-overexpressing plants had decreased mechanical strength and cellulose content, but exhibited increases in the expression of several cellulose synthase genes. These results indicate that OspPLAIIIα plays a role in rice vegetative and reproductive growth and that the constitutive, high activity of OspPLAIIIα suppresses cell elongation. The decreased gibberellin response in overexpressing plants is probably a result of the decreased ability to make cellulose for anisotropic cell expansion.

Increased expression of phospholipase Dα1 in guard cells decreases water loss with improved seed production under drought in Brassica napus.

The activation of phospholipase Dα1 (PLDα1) produces lipid messenger phosphatidic acid and promotes stomatal closure in Arabidopsis. To explore the use of the PLDα1-mediated signalling towards decreasing water loss in crop plants, we introduced Arabidopsis PLDα1 under the control of a guard cell-specific promoter AtKatIpro into two canola (Brassica napus) cultivars. Multiple AtKatIpro ::PLDα1 lines in each cultivar displayed decreased water loss and improved biomass accumulation under hyperosmotic stress conditions, including drought and high salinity. Moreover, AtKatIpro ::PLDα1 plants produced more seeds than did WT plants in fields under drought. The results indicate that the guard cell-specific expression of PLDα1 has the potential to improve crop yield by enhancing drought tolerance.

The functions of phospholipases and their hydrolysis products in plant growth, development and stress responses.

Cell membranes are the initial site of stimulus perception from environment and phospholipids are the basic and important components of cell membranes. Phospholipases hydrolyze membrane lipids to generate various cellular mediators. These phospholipase-derived products, such as diacylglycerol, phosphatidic acid, inositol phosphates, lysophopsholipids, and free fatty acids, act as second messengers, playing vital roles in signal transduction during plant growth, development, and stress responses. This review focuses on the structure, substrate specificities, reaction requirements, and acting mechanism of several phospholipase families. It will discuss their functional significance in plant growth, development, and stress responses. In addition, it will highlight some critical knowledge gaps in the action mechanism, metabolic and signaling roles of these phospholipases and their products in the context of plant growth, development and stress responses.

Phospholipase D- and phosphatidic acid-mediated signaling in plants.

The phospholipase D (PLD) family in higher plants is composed of multiple members, and each of the Arabidopsis PLDs characterized displays distinguishable properties in activity regulation and/or lipid preferences. The molecular and biochemical heterogeneities of the plant PLDs play important roles in the timing, location, and amount of phosphatidic acid (PA) produced. PLD-catalyzed production of PA has been shown to play important roles in plant growth, development, and response to various stresses, including drought, salinity, freezing, and nutrient deficiency. PLD and PA affect cellular processes through different modes of action, including direct target protein binding and biophysical effects on cell membranes. Improved knowledge on the mechanism by which specific PLDs and PA mediate given plant responses will facilitate the understanding of the molecular processes that connect the stimulus perception on membranes to intracellular actions and physiological responses.