[show abstract][hide abstract] ABSTRACT: Phospholipase A(2) (PLA(2)) hydrolyzes phospholipids at the sn-2 position to yield lysophospholipids and free fatty acids. Of the four paralogs expressed in Arabidopsis, the cellular functions of PLA(2)α in planta are poorly understood. The present study shows that PLA(2)α possesses unique characteristics in terms of spatiotemporal subcellular localization, as compared with the other paralogs that remain in the ER and/or Golgi apparatus during secretory processes. Only PLA(2)α is secreted out to extracellular spaces, and its secretion to apoplasts is modulated according to the developmental stages of plant tissues. Observation of PLA(2)α-RFP transgenic plants suggests that PLA(2)α localizes mostly at the Golgi bodies in actively growing leaf tissues, but is gradually translocated to apoplasts as the leaves become mature. When Pseudomonas syringae pv.~tomato DC3000 carrying the avirulent factor avrRpm1 infects the apoplasts of host plants, PLA(2)α rapidly translocates to the apoplasts where bacteria attempt to become established. PLA(2)α promoter::GUS assays show that PLA(2)α gene expression is controlled in a developmental stage- and tissue-specific manner. It would be interesting to investigate if PLA(2)α functions in plant defense responses at apoplasts where secreted PLA(2)α confronts with invading pathogens.
[show abstract][hide abstract] ABSTRACT: The phospholipase A(2) (PLA(2)) superfamily of lipolytic enzymes is involved in a number of essential biological processes, such as inflammation, development, host defense, and signal transduction. Despite the proven involvement of plant PLA(2)s in many biological functions, including senescence, wounding, elicitor and stress responses, and pathogen defense, relatively little is known about plant PLA(2)s, and their genes essentially remain uncharacterized. We characterized three of four Arabidopsis thaliana PLA(2) paralogs (PLA(2)-β, -γ, and -δ) and found that they (1) are expressed during pollen development, (2) localize to the endoplasmic reticulum and/or Golgi, and (3) play critical roles in pollen development and germination and tube growth. The suppression of PLA(2) using the RNA interference approach resulted in pollen lethality. The inhibition of pollen germination by pharmacological PLA(2) inhibitors was rescued by a lipid signal molecule, lysophosphatidyl ethanolamine. Based on these results, we propose that plant reproduction, in particular, male gametophyte development, requires the activities of the lipid-modifying PLA(2)s that are conserved in other organisms.
The Plant Cell 01/2011; 23(1):94-110. · 9.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: Phospholipase A(2) (PLA(2)), which hydrolyzes a fatty acyl chain of membrane phospholipids, has been implicated in several biological processes in plants. However, its role in intracellular trafficking in plants has yet to be studied. Here, using pharmacological and genetic approaches, the root hair bioassay system, and PIN-FORMED (PIN) auxin efflux transporters as molecular markers, we demonstrate that plant PLA(2)s are required for PIN protein trafficking to the plasma membrane (PM) in the Arabidopsis thaliana root. PLA(2)alpha, a PLA(2) isoform, colocalized with the Golgi marker. Impairments of PLA(2) function by PLA(2)alpha mutation, PLA(2)-RNA interference (RNAi), or PLA(2) inhibitor treatments significantly disrupted the PM localization of PINs, causing internal PIN compartments to form. Conversely, supplementation with lysophosphatidylethanolamine (the PLA(2) hydrolytic product) restored the PM localization of PINs in the pla(2)alpha mutant and the ONO-RS-082-treated seedling. Suppression of PLA(2) activity by the inhibitor promoted accumulation of trans-Golgi network vesicles. Root hair-specific PIN overexpression (PINox) lines grew very short root hairs, most likely due to reduced auxin levels in root hair cells, but PLA(2) inhibitor treatments, PLA(2)alpha mutation, or PLA(2)-RNAi restored the root hair growth of PINox lines by disrupting the PM localization of PINs, thus reducing auxin efflux. These results suggest that PLA(2), likely acting in Golgi-related compartments, modulates the trafficking of PIN proteins.
The Plant Cell 06/2010; 22(6):1812-25. · 9.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: Phospholipase A(2) (PLA(2)) catalyses the hydrolysis of phospholipids into lysophospholipids and free fatty acids. Physiological studies have indicated that PLA(2) is involved in stomatal movement. However, genetic evidence of a role of PLA(2) in guard cell signalling has not yet been reported. To identify PLA(2) gene(s) that is (are) involved in light-induced stomatal opening, stomatal movement was examined in Arabidopsis thaliana plants in which the expression of PLA(2) isoforms was reduced or knocked-out. Light-induced stomatal opening in PLA(2)alpha knockout plants did not differ from wild-type plants. Plants in which PLA(2)beta was silenced by RNA interference exhibited delayed light-induced stomatal opening, and this phenotype was reversed by exogenous lysophospholipids, which are products of PLA(2). Stomatal opening in transgenic plants that over-expressed PLA(2)beta was faster than wild-type plants. The expression of PLA(2)beta was localized to the endoplasmic reticulum of guard cells, and increased in response to light in the mature leaf. Aristolochic acid, which inhibits light-induced stomatal opening, inhibited the activity of purified PLA(2)beta. Collectively, these results provide evidence that PLA(2)beta is involved in light-induced stomatal opening in Arabidopsis.
Journal of Experimental Botany 09/2008; 59(13):3587-94. · 5.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: Jasmonic acid (JA) plays pivotal roles in diverse plant biological processes, including wound response. Chloroplast lipid hydrolysis is a critical step for JA biosynthesis, but the mechanism of this process remains elusive. We report here that DONGLE (DGL), a homolog of DEFECTIVE IN ANTHER DEHISCENCE1 (DAD1), encodes a chloroplast-targeted lipase with strong galactolipase and weak phospholipase A(1) activity. DGL is expressed in the leaves and has a specific role in maintaining basal JA content under normal conditions, and this expression regulates vegetative growth and is required for a rapid JA burst after wounding. During wounding, DGL and DAD1 have partially redundant functions for JA production, but they show different induction kinetics, indicating temporally separated roles: DGL plays a role in the early phase of JA production, and DAD1 plays a role in the late phase of JA production. Whereas DGL and DAD1 are necessary and sufficient for JA production, phospholipase D appears to modulate wound response by stimulating DGL and DAD1 expression.
[show abstract][hide abstract] ABSTRACT: Phospholipase A2s (PLA2s) are enzymes that liberate lysophospholipids and free fatty acids (FFAs) from membrane phospholipids in response to hormones and other external stimuli. This report describes the cloning and functional characterization of a PLA2 cDNA from Arabidopsis thaliana, AtsPLA2-alpha, which represents one of four secretory PLA2 (sPLA2) genes in Arabidopsis. The encoded protein is 148-amino acid polypeptide and is predicted to contain a 20-amino acid signal peptide at its amino terminus. The predicted mature form (Mr=14,169) of AtsPLA2-alpha exhibited approximately 5 times the specific activity of its pre-processed form. Different from animal sPLA2s, AtsPLA2-alpha showed a significant preference for the acyl group linoleic acid over palmitic acid in phospholipid hydrolysis. Like some animal sPLA2s, however, it has a slight preference for phosphatidylethanolamine over phosphatidylcholine as the substrate. The specific activity of AtsPLA2-alpha continuously increased as the Ca2+ concentration was increased to 10 mM, and the optimal pH range was very broad and biphasic between 6 and 11. AtsPLA2-alpha transcript was detected at low levels in roots, stems, leaves, and flowers but not in siliques.
Biochimica et Biophysica Acta 10/2005; 1736(2):144-51. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Multiple secretory phospholipase A2 (sPLA2) genes have been identified in plants and encode isoforms with distinct regulatory and catalytic properties. Elucidation of this genetic and biochemical heterogeneity has provided important clues to the regulation and function of the individual enzymes. An increasing body of evidence shows that their lipid products, lysophospholipids and free fatty acids, mediate a variety of cellular responses, including plant growth, development, and responses to stress and defense. This review discusses the newly-acquired information on plant sPLA2s including the molecular and biochemical characteristics, and signaling functions of each isoform.
Progress in Lipid Research 02/2005; 44(1):52-67. · 10.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dandelion plants, the genus Taraxacum, are used in herbal medicine owing to their choleretic, diuretic and anti-carcinogenic activities and several medicinal compounds have been isolated from the roots of these plants. Metabolic manipulation of secondary metabolite biosynthesis is a potential strategy to improve the production of high-value secondary metabolites. The enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) is known to control a key regulatory step in the isoprenoid pathway. We report an efficient transformation protocol for stable introduction of HMGR into dandelion plants (Taraxacum platycarpum H. Dablstaed), which is essential for the biotechnological approach. The Agrobacterium tumefaciens strain EHA105 containing the binary vector, pCAMBIA1301, with GUS and HMGR genes, showed high transformation efficiency after 3–5 week hygromycin selection. Southern blotting, GUS staining and RT-PCR analyses demonstrated stable integration of one copy of the HMGR gene into the dandelion genome. Expression of the integrated genes was particularly eminent in root tissues of primary transformant plants. The establishment of an efficient transformation method may facilitate the improvement of medicinal plant in terms of the accumulation levels of secondary metabolites.
Plant Cell Tissue and Organ Culture 12/2004; 80(1):51-57. · 3.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Evidence is rapidly mounting that phospholipid-derived molecules act as secondary signal messengers in plant signaling. Recent studies have significantly advanced our understanding of phospholipase A (PLA) signaling in plant growth and development, and abiotic and biotic stress responses. The PLA superfamily includes a broad range of enzymes defined by their ability to catalyze the hydrolysis of the ester bonds of their substrate phospholipids. The hydrolysis products of these reactions (free fatty acids and lysophospholipids) have recently been found to perform many important roles. Here, I describe the current classification of various PLAs that have been identified in plants, including Arabidopsis, and recent advances in our understanding of how these PLAs are involved in various cellular signaling pathways.
Trends in Plant Science 06/2004; 9(5):229-35. · 11.81 Impact Factor
[show abstract][hide abstract] ABSTRACT: 5-Epi-aristolochene synthase (EAS) from Capsicum annuum was introduced into the rice genome under the control of a maize ubiquitin promoter by Agrobacterium-mediated transformation. Fifteen independent transgenic rice plants were isolated and characterized. The integration and expression of the transgene were verified through the use of Southern, Northern, and Western blot analyses. The heterologous expression of EAS in transgenic rice did not interfere with the activities of endogenous squalene synthase (SS) or farnesyl diphosphatase (FDPase), in which both enzymes used the same substrate-farnesyl diphosphate (FDP), for the production of squalene and farnesol, respectively. Transgenic rice cells exhibited the induction of EAS enzyme activity upon elicitor (N-acetylchitohexaose) and jasmonic acid (JA) treatments. The induction of EAS enzyme activity was accompanied by an increase in EAS mRNA when challenged by the elicitor. Results indicated that the maize ubiquitin promoter was upregulated upon jasmonic acid and elicitor treatments. Results also show that the EAS ectopic expression in transgenic rice plants resulted in the synthesis of 5-epi-aristolochene in vivo upon elicitor treatment, suggesting that the heterologous expression of pepper EAS is coupled with the endogenous biosynthetic pathway channel of isoprenoid in rice cells.
[show abstract][hide abstract] ABSTRACT: Plant secretory phospholipases A(2) (sPLA(2)s) probably play important roles in phospholipid signaling based on the data reported from other organisms, but their functions are poorly understood because of the lack of cloned sPLA(2) genes. In this study, we cloned and characterized an Arabidopsis secretory phospholipase A(2)-gamma (AtsPLA(2)-gamma) cDNA, and examined its enzymatic properties. The recombinant protein of AtsPLA(2)-gamma showed maximal enzyme activity at pH 8.0, and required Ca(2+) for activity. Moreover, AtsPLA(2)-gamma showed sn-2 position specificity but no prominent acyl preference, though it showed head group specificity to phosphatidylethanolamine rather than to phosphatidylcholine. AtsPLA(2)-gamma was found to predominate in the mature flower rather than in other tissues, and subcellular localization analysis confirmed that AtsPLA(2)-gamma is secreted into the intercellular space.
[show abstract][hide abstract] ABSTRACT: To elucidate the cellular functions of phospholipase A(2) in plants, an Arabidopsis cDNA encoding a secretory low molecular weight phospholipase A(2) (AtsPLA(2)beta) was isolated. Phenotype analyses of transgenic plants showed that overexpression of AtsPLA(2)beta promotes cell elongation, resulting in prolonged leaf petioles and inflorescence stems, whereas RNA interference-mediated silencing of AtsPLA(2)beta expression retards cell elongation, resulting in shortened leaf petioles and stems. AtsPLA(2)beta is expressed in the cortical, vascular, and endodermal cells of the actively growing tissues of inflorescence stems and hypocotyls. AtsPLA(2)beta then is secreted into the extracellular spaces, where signaling for cell wall acidification is thought to occur. AtsPLA(2)beta-overexpressing or -silenced transgenic plants showed altered gravitropism in inflorescence stems and hypocotyls. AtsPLA(2)beta expression is induced rapidly by auxin treatment and in the curving regions of inflorescence stems undergoing the gravitropic response. These results suggest that AtsPLA(2)beta regulates the process of cell elongation and plays important roles in shoot gravitropism by mediating auxin-induced cell elongation.
The Plant Cell 10/2003; 15(9):1990-2002. · 9.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: Plant secretory phospholipases A2 (sPLA2s) probably play important roles in phospholipid signaling based on the data reported from other organisms, but their functions are poorly understood because of the lack of cloned sPLA2 genes. In this study, we cloned and characterized an Arabidopsis secretory phospholipase A2-γ (AtsPLA2-γ) cDNA, and examined its enzymatic properties. The recombinant protein of AtsPLA2-γ showed maximal enzyme activity at pH 8.0, and required Ca2+ for activity. Moreover, AtsPLA2-γ showed sn-2 position specificity but no prominent acyl preference, though it showed head group specificity to phosphatidylethanolamine rather than to phosphatidylcholine. AtsPLA2-γ was found to predominate in the mature flower rather than in other tissues, and subcellular localization analysis confirmed that AtsPLA2-γ is secreted into the intercellular space.
Febs Letters - FEBS LETT. 01/2003; 553(1):113-118.
[show abstract][hide abstract] ABSTRACT: Hevea brasiliensis is an important plant species currently cultivated for the commercial production of natural rubber. As the demand for rubber continues to increase, it is important to identify alternative sources of natural rubber and to increase plant rubber content using molecular approaches. Taraxacum kok-saghyz, a Russian dandelion, produces natural rubber that is of high quality. In this study, the SMALL RUBBER PARTICLE PROTEIN (SRPP) promoter from H. brasiliensis was characterized to determine its suitability for the expression of latex-specific genes in Taraxacum brevicorniculatum which is another Russian dandelion species of T. kok-saghyz from the similar geographical areas. Studies using transgenic Taraxacum plants carrying the SRPP promoter::β-glucuronidase (GUS) sequence indicate that the SRPP promoter does induce gene expression primarily in laticiferous tissues. Additionally, the promoter was regulated by various external conditions including light, tapping, and cold. These findings suggest that the SRPP promoter will be a useful molecular tool for the manipulation of gene expression in the laticiferous tissues of Taraxacum plant species.
Industrial Crops and Products 40:219–224. · 2.47 Impact Factor