Free fatty acid biosynthesis precursors are involved in pollen–stigma interactions in <i>Brassica</i>

Self-incompatibility (SI) is a complex molecular mechanism in flowering plants that prevents self-fertilization and promotes outcrossing. We conducted metabolome analysis of ornamental kale (<i>Brassica oleracea</i> var. <i>acephala</i>) pistils following SI and compatible pollination (CP), revealing significant alterations in lipid metabolism, particularly the accumulation of free fatty acid (FFA) metabolites during CP. Treatment of stigmas with acetyl-CoA and malonyl-CoA, key precursors in fatty acid (FA) synthesis, broke down SI and enhanced CP. Conversely, inhibiting acetyl-CoA carboxylase (ACCase), the rate-limiting enzyme in <i>de novo</i> FA synthesis, significantly reduced compatible pollen attachment and tube growth, highlighting the critical role of FA metabolism in mediating pollination success. We identified a novel interaction between the FERONIA (BoFER) receptor kinase and the biotin carboxyl carrier protein 1 (BoBCCP1), a subunit of the ACCase complex. Suppressing the expression of <i>BoBCCP1</i> in the stigma reduced CP response, suggesting that the FER-BCCP1 module may play a crucial role in regulating FA biosynthesis and determining the outcome of pollen-stigma interactions. Our findings provide new insights into the identification of key metabolic pathways and signaling modules controlling pollen-stigma interactions, and offer a valuable resource for the targeted improvement of <i>Brassica</i> crop breeding.