Seeds are vital for plant reproduction and agriculture. Their size is intricately controlled by genetic signals and environmental factors. While the plant hormone jasmonate (JA) is known to help plants respond to environmental challenges like pests and salt stress, its specific role in regulating seed development remained unclear.

In a study published in The Plant Cell, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences revealed a novel mechanism by which the plant hormone jasmonate  regulates seed size, a crucial trait for plant adaptation and crop yield. They discovered that the jasmonate signaling pathway acts as a negative regulator of seed size in the model plant Arabidopsis thaliana.

The researchers investigated the role of jasmonate in regulating the seed size of Arabidopsis thaliana and revealed how the CORONATINE INSENSITIVE1 (COI1)-mediated jasmonate signaling pathway affected seed growth by inhibiting the expression of KLUH (KLU) gene, a key promoter of seed coat cell growth. Blocking jasmonate signaling resulted in significantly larger seeds, confirming jasmonate's role in limiting size. Jasmonate signaling components are highly active in the seed coat during development.

Furthermore, the researchers explored the interaction between jasmonate ZIM-DOMAIN (JAZ) repressors and two transcription factors, SUPPRESSOR OF DA1-1 (SOD7) and DEVELOPMENT-RELATED PcG TARGET IN THE APEX4 (DPA4). The jasmonate signaling repressor protein JAZ interacts with SOD7 and competes with it for binding to the jasmonate transcription factors MYC2/4. SOD7 and MYC2/4 work together to strongly repress KLU expression, restricting seed size.

In addition, the JA-SOD7-KLU regulatory mechanism plays a critical role under salt stress, highlighting its importance in environmental adaptation. SOD7 also interacts with the germination regulator ABI5, suggesting it may coordinate seed development and germination.

"Our work unveils a sophisticated molecular circuit where JA signaling, through key interactions between JAZ, MYC, SOD7, and KLU, fine-tunes seed size," said HU Yanru and HAN Xiao of XTBG. "Understanding these mechanisms is vital for deciphering how plants balance growth with environmental adaptation and offers potential strategies for improving crop traits."

Published:18 July 2025