ABA-auxin cascade regulates crop root angle in response to drought

Xiong, Yali; Song, Xiaoyun; Mehra, Poonam; Yu, Suhang; Li, Qiaoyi; Tashenmaimaiti, Dilixiadanmu; Bennett, Malcolm; Kong, Xiuzhen; Bhosale, Rahul; Huang, Guoqiang

Abstract

Enhancing drought resistance through the manipulation of root system architecture (RSA) in crops represents a crucial strategy for addressing food insecurity challenges. Abscisic acid (ABA) plays important roles in drought tolerance; yet, its molecular mechanisms in regulating RSA, especially in cereal crops, remain unclear. In this study, we report a new mechanism whereby ABA mediates local auxin biosynthesis to regulate root gravitropic response, thereby controlling the alteration of RSA in response to drought in cereal crops. Under drought conditions, wild-type (WT) plants displayed a steep root angle compared with normal conditions, while ABA biosynthetic mutants (mhz4, mhz5, osaba1, and osaba2) showed a significantly shallower crown root angle. Gravitropic assays revealed that ABA biosynthetic mutants have reduced gravitropic responses compared with WT plants. Hormone profiling analysis indicated that the mhz5 mutant has reduced auxin levels in root tips, and exogenous auxin (naphthaleneacetic acid [NAA]) application restored its root gravitropic defects. Consistently, auxin reporter analysis in mhz5 showed a reduced auxin gradient formation in root epidermis during gravitropic bending response compared with WT plants. Furthermore, NAA, rather than ABA, was able to rescue the compromised gravitropic response in the auxin biosynthetic mutant mhz10-1/tryptophan amino transferase2 (ostar2). Additionally, the maize ABA biosynthetic mutant viviparous5 (vp5) also showed gravitropic defects and a shallower seminal root angle than WT plants, which were restored by external auxin treatment. Collectively, we suggest that ABA-induced auxin synthesis governs the root gravitropic machinery, thereby influencing root angle in rice, maize, and possibly other cereal crops.

Citation

Xiong, Y., Song, X., Mehra, P., Yu, S., Li, Q., Tashenmaimaiti, D., Bennett, M., Kong, X., Bhosale, R., & Huang, G. (2025). ABA-auxin cascade regulates crop root angle in response to drought. Current Biology, 35(3), 542-553.e4. https://doi.org/10.1016/j.cub.2024.12.003

• Journal Article Type: Article
• Acceptance Date: Dec 3, 2024
• Online Publication Date: Jan 10, 2025
• Publication Date: Feb 3, 2025
• Deposit Date: Mar 24, 2025
• Publicly Available Date: Jan 11, 2026
• Journal: Current Biology
• Print ISSN: 0960-9822
• Electronic ISSN: 1879-0445
• Publisher: Cell Press
• Peer Reviewed: Peer Reviewed
• Volume: 35
• Issue: 3
• Pages: 542-553.e4
• DOI: https://doi.org/10.1016/j.cub.2024.12.003
• Keywords: ABA, auxin biosynthesis, root angle gravitropism, cereal crops
• Public URL: https://nottingham-repository.worktribe.com/output/45862678
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0960982224016439?via%3Dihub