cAMP acts as a second messenger in pollen tube growth and reorientation

Abstract

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 Ϸ100 -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.

Cyclic nucleotide‐gated channels in plants

“…Other CNGCs were also expressed in the developing male gametophyte but not exclusively. These data strongly suggest a role for CNGCs in pollen development, consistent with previous evidence for the involvement of cNMPs and Ca 2+ in pollen growth and orientation [3]. Therefore, plant CNGCs are involved in different physiological roles throughout plant development.…”

Novel type of adenylyl cyclase participates in tabtoxinine-β-lactam-induced cell death and occurrence of wildfire disease inNicotiana benthamiana

“…1C). 13,14 To analyze the involvement of NbAC on TβL-induced necrotic wildfire lesions, we created NbAC-silenced N. benthamiana. Results of qRT-PCR analysis suggested that NbAC was well-silenced ( Fig.…”

“…18,19 Plant AC has been isolated and enzymatic properties were also analyzed in Zea mays and A. thaliana, indicating AC is in plants. 13,14 In this study, we isolated AC (NbAC) from N. benthamiana (Fig. 1A,B).…”

“…17 For example, plant AC is closely associated with signaling cascade for pollen tube growth, 14 and cAMP have been shown to regulate Ca 2+ signaling in N. plumbaginofolia protoplasts. 20 In addition, it has been reported that self-incompatibility is associated with the level of cAMP in pistils after pollination, and the level of cAMP depends on AC activity.…”

Cyclic nucleotide-gated channel 18 is an essential Ca 2+ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis

“…These data demonstrate that CNGC18 is the main Ca 2+ channel essential for pollen tube guidance in Arabidopsis. CNGCs are downstream targets of cyclic nucleotides (cAMP and cGMP), and cAMP has been reported to function as a second messenger in pollen tube orientation by regulating Ca 2+ channel activity in pollen tubes (34,44,45). Then, we focused on the six CNGCs, especially CNGC18, in further experiments.…”