Effects of Intracellular Calcium Antagonist, TMB-8, on the Construction of Pollen Tube Wall in Pinus bungeana

Abstract:

The effects of TMB-8, an intracellular calcium antagonist, on the pollen tube growth and cell wall construction in Pinus bungeana were investigated by means of fluorescence microscopy, laser scanning confocal microscopy, immunofluorescence technique and Fourier transform infra-red (FTIR) microspectroscopy. The results showed that TMB-8 inhibited P. bungeana pollen germination and tube growth in a dose-dependent manner. Normally growing pollen tubes displayed a typical tip-focused cytosolic free Ca²⁺ concentration gradient, while the Ca²⁺ concentration gradient dissipated in TMB-8-treated pollen tubes. Cellulose and callose were distributed uniformly in the wall of pollen tubes; acidic pectin was distributed in the tube wall except for the apex while esterified pectin was present only in the apex. In TMB-8-treated tubes, the content of cellulose, acidic pectin and callose increased while esterified pectin decreased in the apex compared with the normal tube wall. It indicated that the intracellular Ca²⁺ was necessary in the formation of apical cytosolic Ca²⁺ concentration gradient. Inhibition of intracellular Ca²⁺ release resulted in the arrest of pollen tube growth by the modification of cell wall composition in P. bungeana pollen tube.