Involvement of phosphoinositide turnover in tracheary element differentiation in Zinnia elegans L. cells

Abstract

Mesophyll cells of Zinnia elegans L., cultured in the presence of phytohormones, will transdifferentiate and undergo programmed cell death to become tracheary elements, thick-walled cells of the xylem. This system is a model system for study of plant cell development and differentiation. We report that a high concentration of extracellular Ca(2+) is necessary during the first 6 h of culturing for tracheary elements to form. Extracellular Ca(2+) is still required at later times, but at a much lower concentration. When cells transdifferentiate in adequate Ca(2+), microsomal phospholipase C activity increases and levels of inositol 1,4,5-trisphosphate rise at about hour 4 of culturing. The production of inositol 1,4,5-trisphosphate appears to be important for tracheary element formation, since inhibitors of phospholipase C inhibit both inositol 1,4,5-trisphosphate production and tracheary element formation. Pertussis toxin, an inhibitor of GTP-binding proteins, inhibits transdifferentiation and eliminates inositol 1,4,5-trisphosphate production. Tracheary element formation was not completely abolished by inhibitors that eliminated inositol 1,4,5-trisphosphate production, suggesting the involvement of other pathways in regulating transdifferentiation.

Cryptogein-Induced Initial Events in Tobacco BY-2 Cells: Pharmacological Characterization of Molecular Relationship among Cytosolic Ca2+ Transients, Anion Efflux and Production of Reactive Oxygen Species

“…3A), the first peak of the response is likely due to an influx of extracellular Ca 2+ , whereas the second peak is due to a release of Ca 2+ into the cytoplasm from intracellular stores through IP 3 -dependent signaling pathway. Phospholipase C is also activated by Ca 2+ in plants as well as in animals (Miyakawa et al 2001, Zhang et al 2002. The Ca 2+ influx during the first peak of the response may participate in the activation of phospholipase C. Interestingly, oligosaccharide elicitors such as β-glucan, chitoheptaose and oligogalacturonides induce similar [Ca 2+ ] cyt transient peaks (Mithöfer et al 1999, Lecourieux et al 2002, suggesting that signals from different kinds of elicitors are mediated by similar Ca 2+ signaling pathways.…”

“…3A), suggesting that increases in [Ca 2+ ] cyt are due to the influx of extracellular Ca 2+ . Phospholipase C, an enzyme producing IP 3 , is inhibited by neomycin and U-73122 (Zhang et al 2002). Neither of these inhibitors affected the first peak of the [Ca 2+ ] cyt transients, while both inhibited the second peak (Fig.…”

The G-Protein-Coupled Receptor GCR1 Regulates DNA Synthesis through Activation of Phosphatidylinositol-Specific Phospholipase C

“…1A). To look at the role of PI-PLC, we examined the effect of the PI-PLC inhibitor U73122 on DNA synthesis, because it is known that U73122 inhibits PI-PLC activity of different types of plant cells, both in vivo and in vitro (Coursol et al, 2000;Zhang et al, 2002). U73122 was added to the cells at concentration of 100 M, as in other studies with plant cells (Perera et al, 2001;Takahashi et al, 2001).…”

“…PLC activity was measured on microsomal membrane preparations, according to the method described by Zhang et al (2002) with a few modifications. Membrane protein (10 g) was incubated with 5 L of substrate micelles in a 50-L final volume of PLC assay buffer for 30 min at 37°C.…”

Rapid accumulation and metabolism of polyphosphoinositol and its possible role in phytoalexin biosynthesis in yeast elicitor-treated Cupressus lusitanica cell cultures

“…Since a free Ca 2+ pulse in the cytosol is one of the most important events in plant defense responses (Trewavas and Mahlo 1998), linking the Ins(1,4,5)P 3 signaling pathway with Ca 2+ signaling extends the influence of Ins(1,4,5)P 3 signal transduction to other cellular processes of plants. In fact, Ins(1,4,5)P 3 -Ca 2+ signal transduction has been suggested to be involved in many cellular processes, such as abscisic acid (ABA)-induced stomatal closure (Gilroy et al 1990;Staxe´n et al 1999;Hunt et al 2003), pollen tube growth (Franklin-Tong et al 1996), tracheary element differentiation (Zhang et al 2002), gravity perception (Perera et al 1999), and elicitor response (Kurosaki et al 1987;Legendre et al 1993;Walton et al 1993). Recent studies have revealed that there are at least two regulatory means to terminate Ins(1,4,5)P 3 signaling pathway in plants; these are Ins(1,4,5)P 3 hydrolysis by 5¢-phosphatase and Ins(1,4,5)P 3 1¢-phosphatase .…”