J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (7): 1670-1686.DOI: 10.1111/jipb.13487

• Abiotic Stress Responses • Previous Articles     Next Articles

The endo-beta mannase MAN7 contributes to cadmium tolerance by modulating root cell wall binding capacity in Arabidopsis thaliana

Qi Wu1,2†, Yu Ting Meng1,2†, Zhi Hang Feng3, Ren Fang Shen1,2 and Xiao Fang Zhu1,2*   

  1. 1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China;
    3. College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
    These authors contributed equally to this work.
    *Correspondence: Xiao Fang Zhu (xiaofangzhu@issas.ac.cn)
  • Received:2022-09-14 Accepted:2023-03-23 Online:2023-03-25 Published:2023-07-01

Abstract: The heavy metal cadmium (Cd) is detrimental to crop growth and threatens human health through the food chain. To cope with Cd toxicity, plants employ multiple strategies to decrease Cd uptake and its root-to-shoot translocation. However, genes that participate in the Cd-induced transcriptional regulatory network, including those encoding transcription factors, remain largely unidentified. In this study, we demonstrate that ENDO-BETA-MANNASE 7 (MAN7) is necessary for the response of Arabidopsis thaliana to toxic Cd levels. We show that MAN7 is responsible for mannase activity and modulates mannose content in the cell wall, which plays a role in Cd compartmentalization in the cell wall under Cd toxicity conditions. Additionally, the repression of root growth by Cd was partially reversed via exogenous application of mannose, suggesting that MAN7-mediated cell wall Cd redistribution depends on the mannose pathway. Notably, we identified a basic leucine zipper (bZIP) transcription factor, bZIP44, that acts upstream of MAN7 in response to Cd toxicity. Transient dual-luciferase assays indicated that bZIP44 directly binds to the MAN7 promoter region and activates its transcription. Loss of bZIP44 function was associated with greater sensitivity to Cd treatment and higher accumulation of the heavy metal in roots and shoots. Moreover, MAN7 overexpression relieved the inhibition of root elongation seen in the bzip44 mutant under Cd toxicity conditions. This study thus reveals a pathway showing that MAN7-associated Cd tolerance in Arabidopsis is controlled by bZIP44 upon Cd exposure.

Key words: Arabidopsis thaliana, bZIP44, cadmium, cell wall, MAN7, mannose

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