Free fatty acid biosynthesis precursors are involved in pollen-stigma interactions in Brassica

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 (Brassica oleracea var. acephala) 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 de novo 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 BoBCCP1 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 Brassica crop breeding.