Ve. Franklintong et al., THE SELF-INCOMPATIBILITY RESPONSE IN PAPAVER-RHOEAS IS MEDIATED BY CYTOSOLIC-FREE CALCIUM, Plant journal, 4(1), 1993, pp. 163-177
The role of Ca2+ signalling during the self-incompatibility (SI) respo
nse in Papaver rhoeas L. has been investigated using Ca2+-sensitive dy
es. Pollen tubes were micro-injected with Calcium Green-1 and cytosoli
c free calcium ([Ca2+]i) imaged using laser scanning confocal microsco
py (LSCM). Addition of incompatible stigmatic S-glycoproteins induced
a transient increase in the level of [Ca2+]i in pollen tubes. In contr
ast, no rise in [Ca2+]i was detectable after addition of either compat
ible or heat-denatured incompatible stigmatic S-glycoproteins. The ele
vation of [Ca2+]i was followed by the specific inhibition of pollen tu
be growth in incompatible reactions. It has been shown previously that
gene expression in pollen tubes is switched on during an incompatible
reaction. Since the [Ca2+]i transient appeared to originate from the
region where the nuclei are located, Ca2+ may be involved in locally r
egulating the expression of these genes. The photoactivation of caged
Ca2+ to artificially elevate [Ca2+]i resulted in the inhibition of pol
len tube growth and thus mimicked the SI response. Taken together, the
results provide an important link between a transient rise in [Ca2+]i
and the biological phenomenon of inhibition of pollen tube growth and
demonstrate, for the first time, direct evidence that the SI response
in P. rhoeas is mediated by [Ca2+]i.