Calcium plays a major role in regulating pollen tube (PT) growth. Calcium levels are oscillatory in nature at the PT tip, along with anion efflux. Calcium has been shown to regulate anion channels in guard cells through calcium protein kinase (CPK) activation. Gutermuth et al. provide evidence for a similar mechanism in PTs. They developed a novel protocol for time-controlled stimulation of calcium entry at PT tips via electrophysiological induction of hyperpolarization pulses. This allows for calcium to enter PTs in a spatially and temporally controlled manner. By this method, calcium entry was sufficient to activate anion channels, confirmed by adding an anion channel inhibitor in tandem with the hyperpolarization-triggered calcium transients which blocked anion channel activity. Loss of various CPKs also resulted in loss of anion channel activity, regardless of this hyperpolarization-triggered calcium increase. Furthermore, loss of CPKs and/or anion channel activity impairs growth of PTs. These data support a model in which calcium induces CPK-dependent anion channel activation necessary for PT growth. (Summary by Alecia Biel) New Phytol. 10.1111/nph.15067.
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