A bHLH transcription factor, OsbHLH168 , represses early seedling growth in rice by modulating the jasmonate signaling pathway

SUMMARY Early seedling growth is a critical phase in the life cycle of rice ( Oryza sativa ) and is particularly sensitive to environmental and hormonal cues. Jasmonic acid (JA) is a key plant hormone known to inhibit growth in various plant species. However, the molecular mechanisms underlying JA‐mediated growth regulation in rice remain to be fully elucidated. This study confirmed that it significantly stunted the growth of wild‐type rice seedlings, reducing shoot length, root length, and lateral root numbers. OsMYC2, a central component of the JA signaling pathway, negatively affects early seedling growth. We identified OsbHLH168 , which also negatively regulates growth. The knockout plants showed enhanced seedling growth, while those overexpressing the gene exhibited significant growth inhibition. Further analysis showed that OsbHLH168 directly binds to and represses the promoter of OsJAZ5 , a crucial negative regulator of the JA pathway. These findings establish OsbHLH168 as a crucial transcriptional repressor in the JA signaling pathway that negatively regulates early seedling growth in rice.