The development of embryos in female figs of Ficus hispida after pollinator entry: transcriptome analysis focusing on hormone dynamics and related signaling genes
Ficus species and their obligate pollinator fig wasps represent classic model systems for exploring mutualistic interactions between species in nature. In dioecious fig species, regardless of whether they enter male or female figs, pollinating fig wasps exhibit both oviposition and pollination behaviors. However, why do flowers in female figs exclusively mature into seeds rather than forming galls to accommodate wasp offspring? So far, no comprehensive study has fully elucidated the intricate molecular mechanisms underlying seed formation in female figs induced by pollinating fig wasps. This study demonstrated that pollen introduced into female figs by pollinating wasps, upon reaching the stigma of female flowers, induces rapid changes in the hormonal profiles of these flowers. Levels of auxin (IAA) and abscisic acid (ABA) increase after pollination, while 1-aminocyclopropane-1-carboxylic acid (ACC) and gibberellin-7 (GA7) decrease. Trans-zeatin (TZ) levels remain stable compared to unpollinated figs. KEGG analysis shows that 11 genes in plant hormone signal transduction pathways are significantly upregulated in pollinated female flowers. Auxin signaling genes activate downstream pathways, enhancing IAA accumulate, which is crucial for embryonic development. After pollination, the development of female fig embryos is regulated by hormones like IAA, ABA, ACC, TZ, and GA7, as well as their signal transduction genes. Auxin homeostasis and nutrient metabolism likely play key roles in embryo development. These findings deepen our understanding of the transcriptional and metabolic regulation of female fig embryogenesis mediated by fig wasps, offer insights into seed formation in Ficus plants, and establish a foundation for investigating the reproductive ecology of this mutualistic interaction.