M. Lenartowska et al., Immunocytochemical localization of esterified and unesterified pectins in unpollinated and pollinated styles of Petunia hybrida Hort., PLANTA, 213(2), 2001, pp. 182-191
Localization of pectins in the style of Petunia hybrida before and after po
llination was investigated by immunocytochemistry using two primary monoclo
nal antibodies specific to highly (JIM7) and weakly (JIM5) methylesterified
pectins. In the unpollinated style, esterified pectins occur-red mainly in
the cell walls of cortex tissue, while unesterified pectins were present m
ainly in the extracellular matrix (ECM) of the transmitting tract. After po
llination no remarkable differences were found in pectin distribution in th
e ground tissue of the style. On the other hand, in the transmitting tract
a reduction in the quantity of unesterified pectins was observed. Unesterif
ied pectins in the extracellular regions of the transmitting tissue decreas
ed before the penetration of the pollen tubes, indicating that pollination
induces a reduction in the amount of unesterified pectins in the transmitti
ng-tract ECM. The correlation between the degradation of strongly Ca2+-bind
ing pectins and the growing level of those ions in the extracellular region
s of the transmitting tract in the pollinated pistil of P. hybrida (M. Lena
rtowska et al. 1997) suggests that this process may constitute a mechanism
for creating an optimum calcium medium for in vivo-growing pollen tubes. Bo
th pectin categories were localized in pollen tubes. Esterified pectin epit
opes were localized mainly in the vesicles of the tip cytoplasm. Unesterifi
ed pectin epitopes were found in the external fibrillar wall of pollen tube
s.