ИСТИНА

Copper and nickel are essential trace elements which serve as cofactors for several enzymes. However, if their homeostasis is disrupted, copper may be involved in excessive ROS production, and both metals can interact with functional groups of macromolecules and substitute cations in metalloenzymes, thereby affecting their properties. The ability of heavy metals to reduce pollen germination efficiency has been known for decades, but mechanisms of their effect remain unclear. The key process ensuring pollen germination and growth is the transport of inorganic ions across the plasma membrane. In the present study we have investigated effects of nickel and copper on this process. Membrane potential was evaluated by quantitative fluorescent microscopy using Di-4-ANEPPS membrane voltage sensor. Both metals affected membrane potential values. Intracellular pH was measured by an optical method using ratiometric BCECF-based technique. Cu2+ application induced pH shift towards alkaline values. The observed effects were consistent with the results of whole-cell patch-clamp experiments. While Ni2+ significantly inhibited the outward К+ current and modestly activated outward Н+ current, Cu2+ has failed to affect К+ current and markedly enhanced Н+ current. Thus, we present the two key plasma membrane targets for heavy metals at the functional level in the pollen grain: potassium channels for Ni2+ and Н+-ATPase for Cu2+. This study was supported by the Russian Foundation for Basic Research (14-04-31431).