Male–female communication triggers calcium signatures during fertilization in Arabidopsis

Cell–cell communication and interaction is critical during fertilization and triggers free cytosolic calcium ([Ca(2+)](cyto)) as a key signal for egg activation and a polyspermy block in animal oocytes. Fertilization in flowering plants is more complex, involving interaction of a pollen tube with egg adjoining synergid cells, culminating in release of two sperm cells and their fusion with the egg and central cell, respectively. Here, we report the occurrence and role of [Ca(2+)](cyto) signals during the entire double fertilization process in Arabidopsis. [Ca(2+)](cyto) oscillations are initiated in synergid cells after physical contact with the pollen tube apex. In egg and central cells, a short [Ca(2+)](cyto) transient is associated with pollen tube burst and sperm cell arrival. A second extended [Ca(2+)](cyto) transient solely in the egg cell is correlated with successful fertilization. Thus, each female cell type involved in double fertilization displays a characteristic [Ca(2+)](cyto) signature differing by timing and behaviour from [Ca(2+)](cyto) waves reported in mammals.