[Show abstract][Hide abstract] ABSTRACT: Plant phospholipase As (PLAs) are classified into two major types, PLA1 and PLA2, according to the hydrolysis sites of their membrane lipids. The lipid products released by PLAs have been suggested to act as bioactive molecules that mediate cellular signaling pathways functioning in plant growth and development, as well as responses to abiotic and biotic stimuli. The past few years have witnessed a wealth of new information regarding the function of these phospholipases in various biological processes. In this chapter, we discuss recent insights into lipid-based signaling mediated by PLAs and their lipid products, with particular emphasis on their emerging role as lipid mediators.
[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.
No preview · Article · Nov 2012 · Industrial Crops and Products
[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.
Full-text · Article · Jun 2012 · Frontiers in Plant Science
[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.
[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.
[Show abstract][Hide abstract] ABSTRACT: Phospholipase A2 (PLA2) catalyses the hydrolysis of phospholipids into lysophospholipids and free fatty acids. Physiological studies have indicated
that PLA2 is involved in stomatal movement. However, genetic evidence of a role of PLA2 in guard cell signalling has not yet been reported. To identify PLA2 gene(s) that is (are) involved in light-induced stomatal opening, stomatal movement was examined in Arabidopsis thaliana plants in which the expression of PLA2 isoforms was reduced or knocked-out. Light-induced stomatal opening in PLA2α knockout plants did not differ from wild-type plants. Plants in which PLA2β was silenced by RNA interference exhibited delayed light-induced stomatal opening, and this phenotype was reversed by exogenous
lysophospholipids, which are products of PLA2. Stomatal opening in transgenic plants that over-expressed PLA2β was faster than wild-type plants. The expression of PLA2β 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 PLA2β. Collectively, these results provide evidence that PLA2β is involved in light-induced stomatal opening in Arabidopsis.
[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.
Full-text · Article · Mar 2008 · Developmental Cell
[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.
Full-text · Article · Feb 2005 · Progress in Lipid Research