Phosphatidic acid produced by phospholipase D is required for tobacco pollen tube growth

Abstract

Phospholipase D (PLD) and its product phosphatidic acid (PA) are involved in a number of signalling pathways regulating cell proliferation, membrane vesicle trafficking and defence responses in eukaryotic cells. Here we report that PLD and PA have a role in the process of polarised plant cell expansion as represented by pollen tube growth. Both phosphatidylinositol-4,5-bisphosphate-dependent and independent PLD activities were identified in pollen tube extracts, and activity levels during pollen tube germination and growth were measured. PLD-mediated PA production in vivo can be blocked by primary alcohols, which serve as a substrate for the transphosphatidylation reaction. Both pollen germination and tube growth are stopped in the presence 0.5% 1-butanol, whereas secondary and tertiary isomers do not show any effect. This inhibition could be overcome by addition of exogenous PA-containing liposomes. In the absence of n-butanol, addition of a micromolar concentration of PA specifically stimulates pollen germination and tube elongation. Furthermore, a recently established link between PLD and microtubule dynamics was supported by taxol-mediated partial rescue of the 1-butanol-inhibited pollen tubes. The potential signalling role for PLD-derived PA in plant cell expansion is discussed.

Exogenous γ-aminobutyric acid (GABA) affects pollen tube growth via modulating putative Ca2+-permeable membrane channels and is coupled to negative regulation on glutamate decarboxylase

“…These components are involved in vesicle trafficking and polarity signal transduction pathways that are crucial for pollen tube tip growth. The heterotrimeric Gβ subunit (Ma et al , 1999) and its possible downstream signalling components PLC3 (Dowd et al , 2006; Helling et al , 2006), PLD (Potocky et al , 2003), MAPK (Wilson et al , 1995), and CDPK2 (calcium-dependent protein kinase) (Yoon et al , 2006) are involved in the regulation of pollen tube growth. Moreover, small G proteins such as Rab2 and Rab11 participate in vesicle trafficking in tobacco pollen tube tip growth (Cheung et al , 2002; de Graaf et al , 2005).…”

“…To understand its relationship to known signalling pathways involved in pollen tube growth, some key components involved in signal transduction and vesicle trafficking in pollen tube growth were tested. Previous research demonstrated that PLC3, PLD, and CDPK are all involved in plasma membrane polarization and polar pollen tube growth (Potocky et al , 2003; Dowd et al , 2006; Helling et al , 2006). The present RT-qPCR results indicated that exogenous GABA significantly stimulates the expression of PLC3 and Rab2 during normal pollen tube growth (Fig.…”

“…Many proteins are involved in the regulation of pollen tube tip growth and vesicle trafficking, including a heterotrimeric G protein (Ma et al , 1999), phospholipase C (PLC) (Dowd et al , 2006; Helling et al , 2006), phospholipase D (PLD) (Potocky et al , 2003), mitogen-activated protein kinases (MAPK) (Wilson et al , 1995), and the Rop/RacGTPase molecular switches and related regulatory molecules (Cheung et al , 2003; Klahre et al , 2006; Klahre and Kost, 2006; Lavy et al , 2007; Szumlanski and Nielsen, 2009). To understand the function of GABA in pollen tube growth, it is therefore necessary to clarify the role of GABA in the complex network comprising these proteins and the pathway(s) in which GABA may be involved.…”

Transcriptional Evidence for Inferred Pattern of Pollen Tube-Stigma Metabolic Coupling during Pollination

“…Potocky et al [62] first reported the importance of PA catalyzed by PLD in the polarized expansion of plant cells. Then, Monteiro et al [63] showed that PtdIns(4,5)P2 and Ins(1,4,5)P3, together with PA, play a vital role in the regulation of cytoplasmic [Ca 2+ ] levels, endo/exocytosis, and vesicular trafficking in the apex of pollen tubes.…”

Formins: Emerging Players in the Dynamic Plant Cell Cortex

“…Also, in poppy pollen tubes, microtubules seem to be important for maintaining growth direction but not for growth as such [16], and extremely high concentrations of the microtubule-stabilizing drug taxol were required to inhibit tobacco pollen tube elongation [17]. …”