J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (12): 2645-2659.DOI: 10.1111/jipb.13581

• Molecular Physiology • Previous Articles     Next Articles

Enhancing maize's nitrogen-fixing potential through ZmSBT3, a gene suppressing mucilage secretion

Jingyang Gao1, Peijiang Feng2, Jingli Zhang2, Chaopei Dong1, Zhao Wang1, Mingxiang Chen2, Zhongliang Yu1, Bowen Zhao1, Xin Hou1, Huijuan Wang2, Zhaokun Wu1, Razia Sultana Jemim2, Haidong Yu2, Doudou Sun2, Pei Jing2, Jiafa Chen2, Weibin Song3, Xuecai Zhang4, Zijian Zhou2* and Jianyu Wu1,2*   

  1. 1. College of Agronomy, State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou 450002, China;
    2. College of Life Sciences, Henan Agricultural University, Zhengzhou 450002, China;
    3. State Key Laboratory of Plant Physiology and Biochemistry, National Maize Improvement Center, College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China;
    4. International Maize and Wheat Improvement Center(CIMMYT), El Batan, Texcoco 56237, Mexico
    *Correspondence:Zijian Zhou(zhouzijian19900601@163.com);Jianyu Wu(wujianyu40@126.com, Dr. Wu is fully responsible for the distributions of all materials associated with this article)
  • Received:2023-06-04 Accepted:2023-11-06 Online:2023-11-06 Published:2023-12-01

Abstract: Maize (Zea mays) requires substantial amounts of nitrogen, posing a challenge for its cultivation. Recent work discovered that some ancient Mexican maize landraces harbored diazotrophic bacteria in mucilage secreted by their aerial roots. To see if this trait is retained in modern maize, we conducted a field study of aerial root mucilage (ARM) in 258 inbred lines. We observed that ARM secretion is common in modern maize, but the amount significantly varies, and only a few lines have retained the nitrogen-fixing traits found in ancient landraces. The mucilage of the high-ARM inbred line HN5-724 had high nitrogen-fixing enzyme activity and abundant diazotrophic bacteria. Our genome-wide association study identified 17 candidate genes associated with ARM across three environments. Knockouts of one candidate gene, the subtilase family gene ZmSBT3, confirmed that it negatively regulates ARM secretion. Notably, the ZmSBT3 knockout lines had increased biomass and total nitrogen accumulation under nitrogen-free culture conditions. High ARM was associated with three ZmSBT3 haplotypes that were gradually lost during maize domestication, being retained in only a few modern inbred lines such as HN5-724. In summary, our results identify ZmSBT3 as a potential tool for enhancing ARM, and thus nitrogen fixation, in maize.

Key words: maize, aerial root, mucilage, nitrogen-fixing, ZmSBT3, GWAS, gene cloning, Diazotroph

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