The Germin‐like protein OsGER4 is involved in promoting crown root development under exogenous jasmonic acid treatment in rice

• Published in: The Plant journal : for cell and molecular biology Vol. 112; no. 3; pp. 860 - 874
• Main Authors: To, Huong Thi Mai, Pham, Dan The, Le Thi, Van Anh, Nguyen, Trang Thi, Tran, Tuan Anh, Ta, Anh Son, Chu, Ha Hoang, Do, Phat Tien
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01-11-2022
• Subjects: abiotic stress; Auxins; Cellular stress response; crown root; Cytokinins; Environmental stress; Gene expression; Genome Wide Association study; Genomes; Germin‐like protein; jasmonates; Jasmonic acid; Oryza sativa; Oryza sativa L. (rice); Phenotyping; Plant tissues; Primordia; Proteins; Rice; Root development; Roots; Vascular tissue
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.15987

SUMMARY
In rice (Oryza sativa L.), crown roots (CRs) have many important roles in processes such as root system expansion, water and mineral uptake, and adaptation to environmental stresses. Phytohormones such as auxin, cytokinin, and ethylene are known to control CR initiation and development in rice. However, the role of jasmonic acid (JA) in CR development remained elusive. Here, we report that JA promotes CR development by regulating OsGER4, a rice Germin‐like protein. Root phenotyping analysis revealed that exogenous JA treatment induced an increase in CR number in a concentration‐dependent manner. A subsequent genome‐wide association study and gene expression analyses pinpointed a strong association between the Germin‐like protein OsGER4 and the increase in CR number under exogenous JA treatment. The ProGER4::GUS reporter line showed that OsGER4 is a hormone‐responsive gene involved in various stress responses, mainly confined to epidermal and vascular tissues during CR primordia development and to vascular bundles of mature crown and lateral roots. Notable changes in OsGER4 expression patterns caused by the polar auxin transport inhibitor NPA support its connection to auxin signaling. Phenotyping experiments with OsGER4 knockout mutants confirmed that this gene is required for CR development under exogenous JA treatment. Overall, our results provide important insights into JA‐mediated regulation of CR development in rice.
Significance Statement
We discovered a Germin‐like protein, OsGER4, while conducting a genome‐wide association study on the induction of crown root development under jasmonic acid‐induced stress using a panel of 155 rice (Oryza sativa L.) accessions. We found that OsGER4 is a hormone‐responsive gene involved in a variety of stress responses. Interestingly, its expression patterns coincided with the auxin distribution patterns during lateral root initiation and crown root emergence. OsGER4 null mutants demonstrated that this gene contributes to crown root development in rice under exogenous JA treatment.