Rac homologues and compartmentalized phosphatidylinositol 4, 5-bisphosphate act in a common pathway to regulate polar pollen tube growth.
Pollen tube cells elongate based on actin- dependent targeted secretion at the tip. Rho family small GTPases have been implicated in the regulation of related processes in animal and yeast cells. We have functionally characterized Rac type Rho family proteins that are expressed in growing pollen tubes. Expression of dominant negative Rac inhibited pollen tube elongation, whereas expression of constitutive active Rac induced depolarized growth. Pollen tube Rac was found to accumulate at the tip plasma membrane and to physically associate with a phosphatidylinositol monophosphate kinase (PtdIns P-K) activity. Phosphatidylinositol 4, 5-bisphosphate (PtdIns 4, 5-P2), the product of PtdIns P-Ks, showed a similar intracellular localization as Rac. Expression of the pleckstrin homology (PH)-domain of phospholipase C (PLC)-delta1, which binds specifically to PtdIns 4, 5-P2, inhibited pollen tube elongation. These results indicate that Rac and PtdIns 4, 5-P2 act in a common pathway to control polar pollen tube growth and provide direct evidence for a function of PtdIns 4, 5-P2 compartmentalization in the regulation of this process.
Kost
B
B
Laboratory of Plant Molecular Biology, The Rockefeller University, New York 10021-6399, USA.
Lemichez
E
E
Spielhofer
P
P
Hong
Y
Y
Tolias
K
K
Carpenter
C
C
Chua
N H
NH
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000502:physiology* / Q000648:ultrastructure; D002478:Cells, Cultured; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D007527:Isoenzymes / Q000378:metabolism; D008969:Molecular Sequence Data; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D054803:Phospholipase C delta; D010940:Plant Proteins / Q000378:metabolism; D018514:Plant Structures; D010947:Plants, Toxic; D011058:Pollen / Q000502:physiology* / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism; D020744:rac GTP-Binding Proteins
D007527:Isoenzymes; D019269:Phosphatidylinositol 4,5-Diphosphate; D010940:Plant Proteins; D011994:Recombinant Proteins; D010738:Type C Phospholipases; D054803:Phospholipase C delta; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins