[Effects of G-protein regulators and stylar S-RNase on the growth and Ca2+ concentration of Pyrus pyrifolia pollen tube]

Abstract

The effects of G protein regulators and stylar S-RNase on the growth and [Ca(2+)](i) changes of the Pyrus pyrifolia pollen tube were investigated using Laser Confocal Scanning Microscope (LCSM). The results indicated that: (1) The growth of 'Housui' pollen tube could be inhibited by its stylar S-RNase and pertussis toxin (PTX), the inhibitor of heterotrimeric G protein. While 'Kousui' stylar S-RNase had little effect on the growth of 'Housui' pollen tube; cholera toxin (CTX), the activator of heterotrimeric G protein, could promote pollen tube growth and eliminate the suppression of stylar S-RNase on the growth of self-pollen tube, but the growth of 'Housui' pollen tube could be arrested under the co-action of PTX and S-RNase from 'Kousui' Fig.1). (2) Treatments with different stylar S-RNase and G protein regulators could have different effects on the change in [Ca(2+)](i) in the tip of pollen tube (Figs.2,3). The treatment with 'Housui' stylar S-RNase could induce the decrease of fluorescence gradient of [Ca(2+)](i) along the tip of self-pollen tube (Figs.2A, 3A), and the treatment with CTX could markedly elevate [Ca(2+)](i) in the tip of pollen tube showed (Fig.3C). The way of [Ca(2+)](i) changed in 'Housui' pollen tube under the co-action of CTX and its stylar S-RNase showed the compositive effect of the two respective treatment (Fig.3A, C, E), but the effect of the co-action of PTX and 'Kousui' stylar S-RNase showed increase in [Ca(2+)](i) in the pollen tube in 18 min after treatment, and then decrease between 18-36 min (Fig.3F). These results suggest that during self or cross pollination, the control of the growth of Pyrus pyrifolia pollen tube is by the synergistic effect of stylar S-RNase, G protein and [Ca(2+)](i) in the pollen tube.