Calcium imaging in Arabidopsis pollen cells using G-CaMP5

Calcium (Ca²⁺ ) signaling has been implicated in pollen germination and pollen tube growth. To date, however, we still know very little about how exactly Ca²⁺ signaling links to various physiological subcellular processes during pollen germination and pollen tube growth. Given that Ca²⁺ signaling is tightly related to the cytosolic concentration and dynamics of Ca²⁺ , it is vital to trace the dynamic changes in Ca²⁺ levels in order to decode Ca²⁺ signaling. Here, we demonstrate that G-CaMP5 serves well as an indicator for monitoring cytosolic Ca²⁺ dynamics in pollen cells. Using this probe, we show that cytosolic Ca²⁺ changes dramatically during pollen germination, and, as reported previously, Ca²⁺ forms a tip-focused gradient in the pollen tube and undergoes oscillation in the tip region during pollen tube growth. In particular, using G-CaMP5 allowed us to capture the dynamic changes in the cytosolic Ca²⁺ concentration ([Ca²⁺ ]_cyt ) in pollen tubes in response to various exogenous treatments. Our data suggest that G-CaMP5 is a suitable probe for monitoring the dynamics of [Ca²⁺ ]_cyt in pollen cells.