Verapamil Affected Pollen Germination and Tube Elongation through Altering Calcium Dynamics, Actin Filaments and Cell Wall Components in Apple (Malus domestica).

Calcium plays an essential role in plant developmental process, especially in pollen tube growth. Verapamil, an inhibitor of calcium channels, could affect extracellular calcium ion influx. The present study aimed to investigate the effect of verapamil on pollen tube growth of Malus domestica and the possible cytological mechanism. Results showed that verapamil affected pollen germination and tube growth in a dose dependent manner. 20 μM verapamil promoted pollen germination and tube growth, while 700 μM verapamil inhibited pollen germination and tube growth. Results from non-invasive ion-selective electrode technique and fluorescent labeling showed that 700 μM verapamil decreased calcium influx and disturbed [Ca2+]c gradient at pollen tube apex. In addition, 700 μM verapamil also affected actin filaments. Further results demonstrated that 700 μM verapamil influenced distribution of pollen tube wall components such as callose, acid pectins and esterified pectins, Fourier-transform infrared analysis (FTIR) of chemical composition supported the above results. In summary, 700 μM verapamil triggered multiple cellular changes including Ca2+ influx, [Ca2+]c gradient, actin filaments and pollen tube wall components. Based on the above results, we speculated that 700 μM verapamil inhibited apical growth of pollen tubes through altering Ca2+ influx, [Ca2+]c gradient, actin filaments and cell wall components. [ABSTRACT FROM AUTHOR]