Details

Autor(en) / Beteiligte

• Monteiro, David
• Liu, Qunlu
• Lisboa, Saskia
• Scherer, G. E. F
• Quader, Hartmut
• Malhó, Rui

Titel

Phosphoinositides and phosphatidic acid regulate pollen tube growth and reorientation through modulation of [Ca²⁺][subscript c] and membrane secretion

Ist Teil von

• Journal of experimental botany, 2005-06, Vol.56 (416), p.1665-1674

Erscheinungsjahr

2005

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The maintenance of a calcium gradient and vesicle secretion in the apex of pollen tubes is essential for growth. It is shown here that phosphatidylinositol-4,5-bisphosphate (PIP₂) and D-myo-inositol-1,4,5-trisphosphate (IP₃), together with phosphatidic acid (PA), play a vital role in the regulation of these processes. Changes in the intracellular concentration of both PIP₂ and IP₃ (induced by photolysis of caged-probes), modified growth and caused reorientation of the growth axis. However, measurements of cytosolic free calcium ([Ca²⁺][subscript c]) and apical secretion revealed significant differences between the photorelease of PIP₂ or IP₃. When released in the first 50 [micro]m of the pollen tube, PIP₂ led to transient growth perturbation, [Ca²⁺][subscript c] increases, and inhibition of apical secretion. By contrast, a concentration of IP₃ which caused a [Ca²⁺][subscript c] transient of similar magnitude, stimulated apical secretion and caused severe growth perturbation. Furthermore, the [Ca²⁺][subscript c] transient induced by IP₃ was spatially different causing a pronounced elevation in the sub-apical region. These observations suggest different targets for the two phosphoinositides. One of the targets is suggested to be PA, a product of PIP₂ hydrolysis via phospholipase C (PLC) or phospholipase D (PLD) activity. It was found that antagonists of PA accumulation (e.g. butan-1-ol) and inhibitors of PLC and PLD reversibly halted polarity. Reduction of PA levels caused the dissipation of the [Ca²⁺][subscript c] gradient and inhibited apical plasma membrane recycling. It was also found to cause abolition of the apical zonation. These data suggest that phosphoinositides and phospholipids regulate tip growth through a multiple pathway system involving regulation of [Ca²⁺][subscript c] levels, endo/exocytosis, and vesicular trafficking.