Pan-family pollen signals control an interspecific stigma barrier across Brassicaceae species
- Yunyun Cao
- Xiaoshuang Cui
- Yinqing Yang
- Lianhui Pan
- Fei Yang
- Shuyan Li
- Dandan Wu
- Yuelan Ding
- Rui CHEN
- Nan Wang
- Shangjia Liu
- Zhaojing Ji
- Yuxuan Zhao
- Yue Chen
- Rui Sun
- Shiyu Xian
- Lin Yang
- Jiyun Hui
- Ru Li
- Tong Zhang
- Shengwei Dou
- Gengxing Song
- Xiaochun Wei
- Yuxiang Yuan
- Xiaowei Zhang
- Mingming Chen
- Xihai Sun
- Hen-Ming Wu
- Alice Y. Cheung
- Qiaohong Duan
2025-11-20
Prezygotic interspecific incompatibility prevents hybridization between species, which limits interbreeding strategies for crop improvement using wild relatives. The Brassica rapa female self-incompatibility determinant, S -locus receptor kinase (SRK), recognizes interspecific pollen. Here, we report the discovery of a pan-Brassicaceae SRK-interacting interspecific pollen signal (SIPS). On B. rapa stigmas, SIPSs from Arabidopsis and other Brassicaceae species target Br SRK and recruit the female fertility regulator FERONIA receptor kinase to increase stigmatic reactive oxygen species and reduce interspecific pollen viability. Arabidopsis thaliana sips mutant pollen failed to trigger interspecific incompatibility responses. Unlike self-incompatibility, which is controlled by the polymorphic S locus, different genetic variants of SRK interacted comparably with SIPS. This study establishes SIPS-SRK as a Brassicaceae-specific ligand-receptor pair that broadly maintains the stigmatic interspecific barrier in self-incompatible species.