Growth of Pollen Tubes of Papaver rhoeas Is Regulated by a Slow-Moving Calcium Wave Propagated by Inositol 1,4,5-Trisphosphate.
A signaling role for cytosolic free Ca2+ ([Ca2+]i) in regulating Papaver rhoeas pollen tube growth during the self-incompatibility response has been demonstrated previously. In this article, we investigate the involvement of the phosphoinositide signal transduction pathway in Ca2+-mediated pollen tube inhibition. We demonstrate that P. rhoeas pollen tubes have a Ca2+-dependent polyphosphoinositide-specific phospholipase C activity that is inhibited by neomycin. [Ca2+]i imaging after photolysis of caged inositol (1,4,5)-trisphosphate (Ins[1,4,5]P3) in pollen tubes demonstrated that Ins(1,4,5)P3 could induce Ca2+ release, which was inhibited by heparin and neomycin. Mastoparan, which stimulated Ins(1,4,5)P3 production, also induced a rapid increase in Ca2+, which was inhibited by neomycin. These data provide direct evidence for the involvement of a functional phosphoinositide signal-transducing system in the regulation of pollen tube growth. We suggest that the observed Ca2+ increases are mediated, at least in part, by Ins(1,4,5)P3-induced Ca2+ release. Furthermore, we provide data suggesting that Ca2+ waves, which have not previously been reported in plant cells, can be induced in pollen tubes.
Franklin-Tong
V. E.
VE
Wolfson Laboratory for Plant Molecular Biology, School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
Drobak
B. K.
BK
Allan
A. C.
AC
Watkins
PAC.
P
Trewavas
A. J.
AJ