Petunia Phospholipase C1 Is Involved in Pollen Tube Growth

• Published in: The Plant cell 2006-06, Vol.18 (6), p.1438-1453
• Main Authors: Dowd, Peter E., Coursol, Sylvie, Skirpan, Andrea L., Kao, Teh-hui, Gilroy, Simon
• Format: Article
• Language: English
• Subjects: Actins; Actins - metabolism; Calcium Signaling; Cell growth; Cell Membrane - metabolism; Cell membranes; Enzymes; Gene Expression; Golgi Apparatus - metabolism; Molecular Sequence Data; Petunia - enzymology; Phosphatidylinositol Diacylglycerol-Lyase - metabolism; Plant cells; Plant growth regulators; Plants; Pollen; Pollen - cytology; Pollen - enzymology; Pollen - growth & development; Pollen tubes; Positron emission tomography; Protein Transport; Recombinant Fusion Proteins - metabolism; Reproduction; Type C Phospholipases - chemistry; Type C Phospholipases - metabolism
• ISSN: 1040-4651; 1532-298X; 1532-298X
• DOI: 10.1105/tpc.106.041582

Although pollen tube growth is essential for plant fertilization and reproductive success, the regulators of the actin-related growth machinery and the cytosolic$\text{Ca}^{2+}$gradient thought to determine how these cells elongate remain poorly defined. Phospholipases, their substrates, and their phospholipid turnover products have been proposed as such regulators; however, the relevant phospholipase(s) have not been characterized. Therefore, we cloned cDNA for a pollen-expressed phosphatidylinositol 4,5-bisphosphate (PtdInsP₂)-cleaving phospholipase C (PLC) from Petunia inflata, named Pet PLC1. Expressing a catalytically inactive form of Pet PLC1 in pollen tubes caused expansion of the apical$\text{Ca}^{2+}$gradient, disruption of the organization of the actin cytoskeleton, and derealization of growth at the tube tip. These phenotypes were suppressed by depolymerizing actin with low concentrations of latrunculin B, suggesting that a critical site of action of Pet PLC1 is in regulating actin structure at the growing tip. A green fluorescent protein (GFP) fusion to Pet PLC1 caused enrichment in regions of the apical plasma membrane not undergoing rapid expansion, whereas a GFP fusion to the PtdInsP₂ binding domain of mammalian PLC δ1 caused enrichment in apical regions depleted in PLC. Thus, Pet PLC1 appears to be involved in the machinery that restricts growth to the very apex of the elongating pollen tube, likely through its regulatory action on PtdInsP₂ distribution within the cell.