Mutation in HER1 enhances stigma exsertion and hybrid seed production in rice

Daiming Guo, Kangxi Du, Peizhou Xu, Su Liu, Mengyuan Li, Jiazhi Dong, Jingcheng Zhao, Mingming Zhang, Gege Zhou, Yong Li, Xinmiao Yuan, Fangli Jin, Zhixue Zhao, Shicong Yu, Duo Xia, Hongyu Zhang, Xiaoqiong Chen, Ming Luo, Asif Ali, Yunfeng Tian, Hao Zhou, Xianjun Wu & Yongxiang Liao

Nat Commun  volume17, Article number:2364 (2026),04 February 2026(IF=18.06)

Abstract

Hybrid rice has achieved a significant leap in rice yield, but the low outcrossing rate of sterile lines limits hybrid seed production due to rice’s self-pollinating habits, constraining the further development and widespread adoption of hybrid rice. Stigma exsertion is a critical trait affecting outcrossing rate. Here we characterize a rice mutant, high exsertion rate1 (her1), characterized by enlarged stigma and enhanced stigma exsertion. HER1 encodes a SET domain-containing protein that binds to histone H3 at methylated lysine 9 and regulates H3K9me2 levels. Loss of function of HER1 results in reduced H3K9me2 levels in her1, increasing the transcription of Downstream2 (DS2), which positively controls stigma size. Using the loss-of-function allele of her1, we develop a high-exsertion male-sterile line herA, which increases hybrid seed production by more than 20% in field conditions, substantiating the breeding value of HER1 in hybrid seed production.