Fuente: PubMed "pollen" Mol Plant. 2026 Aug 18:S1674-2052(26)00268-6. doi: 10.1016/j.molp.2026.08.010. Online ahead of print.ABSTRACTDouble fertilization initiates via signal communication between pollen grains and the stigma of the pistil, a process encompassing pollen adhesion, hydration, germination, and penetration. While several molecular regulators governing pollen hydration and penetration have been characterized, the key molecules that mediate pollen germination on the stigma remain largely unelucidated. In this study, we identified jasmonic acid (JA), a maternally factor secreted by stigmatic papilla cells, which facilitates pollen germination by elevating cytosolic Ca2+ levels in pollen grains. We found that pollen grains exhibited a significantly lower germination speed in vitro compared with germination on stigmas, and this in vitro germination defect could be rescued by exogenous JA supplementation. We showed that stigmatic papilla cells accumulated high concentrations of JA, which was secreted to promote pollen germination. The lack of essential genes for JA synthesis, rather than JA receptor COI1 in stigma, causes defective pollen germination. JA triggered calcium elevation in pollen grains. This calcium signal is required for pollen germination and can be suppressed by calcium channel inhibitors. Annexin 1 (ANN1) and Annexin 2 (ANN2), two calcium channels expressed in pollen grains, were contributed to JA-triggered calcium increasing in pollen grains. We further showed that applying JA on the stigma could promote interspecific pollen germination. In summary, our work reveals a new role for stigma-derived JA in promoting pollen germination by triggering calcium signaling in pollen grains.PMID:42613841 | DOI:10.1016/j.molp.2026.08.010