cAMP acts as a second messenger in pollen tube growth and reorientation.
Pollen tube growth and reorientation is a prerequisite for fertilization and seed formation. Here we report imaging of cAMP distribution in living pollen tubes microinjected with the protein kinase A-derived fluorosensor. Growing tubes revealed a uniform distribution of cAMP with a resting concentration of approximately 100-150 nM. Modulators of adenylyl cyclase (AC), forskolin, and dideoxyadenosine could alter these values. Transient elevations in the apical region could be correlated with changes in the tube-growth axis, suggesting a role for cAMP in polarized growth. Changes in cAMP arise through the activity of a putative AC identified in pollen. This signaling protein shows homology to functional motifs in fungal AC. Expression of the cDNA in Escherichia coli resulted in cAMP increase and complemented a catabolic defect in the fermentation of carbohydrates caused by the absence of cAMP in a cyaA mutant. Antisense assays performed with oligodeoxynucleotide probes directed against conserved motifs perturbed tip growth, suggesting that modulation of cAMP concentration is vital for tip growth.
Moutinho
A
A
Department of Plant Biology, Faculdade de Ciências de Lisboa, University of Lisbon, Block C2, Lisboa, 1749-016 Lisbon, Portugal.
Hussey
P J
PJ
Trewavas
A J
AJ
Malhó
R
R
D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D000595:Amino Acid Sequence; D001483:Base Sequence; D000242:Cyclic AMP / Q000502:physiology*; D019668:Liliaceae / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D008969:Molecular Sequence Data; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D011058:Pollen; D015290:Second Messenger Systems
D020319:Oligodeoxyribonucleotides, Antisense; D010940:Plant Proteins; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; C435727:PsiP protein, Zea mays