ICE1 (Inducer of CBF Expression 1) Is Essential for the Jasmonate‐Regulated Development of Stamen in Arabidopsis thaliana.

Floral organ development, pollen germination and pollen tube growth are crucial for plant sexual reproduction. Phytohormones maintain these processes by regulating the expression and activity of various transcription factors. ICE1, a MYC‐like bHLH transcription factor, has been revealed to be involved in cold acclimatisation of Arabidopsis. This study shows that ICE1 regulates multiple aspects of sexual reproduction, including stamen development, pollen development and germination. Loss‐of‐function mutants of ICE1 exhibit floral organs with shorter filaments, defective anther dehiscence and lower pollen viability compared to the wild type. These abnormalities result in disrupted fertilisation, leading to short siliques, a high rate of seed abortion, and dark, shriveled mature seeds. JAZ proteins (JAZ1 and JAZ9) interact with ICE1, inhibiting its transcriptional activity on jasmonic acid (JA)‐responsive genes, including MYB21, MYB24 and MYB108. This study highlights the essential role of ICE1 as a signalling agent in the JA‐regulated maintenance of sexual reproduction in Arabidopsis thaliana. Summary statement: In Arabidopsis thaliana, jasmonic acid signalling promotes the degradation of JAZ proteins, relieving their inhibition on ICE1. Once activated, ICE1 regulates floral organ and pollen development by stimulating the expression of MYB21, MYB24 and MYB108. [ABSTRACT FROM AUTHOR]