Stigmatic papilla cells secrete jasmonic acid to promote pollen germination through calcium signaling.

Jasmonic acid secreted by stigmatic papilla cells promotes pollen germination by elevating cytosolic Ca2+ levels in pollen grains.

• Why it matters: Pollen germination on the stigma is a key step in double fertilization, yet the stigma-derived molecules and signaling mechanisms that enable it remain largely unclear.
• What they did: The study identified JA as a maternal factor secreted by stigmatic papilla cells; in vitro, exogenous JA rescued slower germination, and gene disruption in JA synthesis (not COI1) impaired germination.
• The result: JA triggered calcium elevation required for germination and was suppressible by calcium channel inhibitors, with Annexin 1 and Annexin 2 contributing to the Ca2+ increase, and JA on the stigma promoted interspecific pollen germination.

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