J Integr Plant Biol. ›› 2021, Vol. 63 ›› Issue (10): 1787-1800.DOI: 10.1111/jipb.13148

• Plant-biotic Interactions • Previous Articles     Next Articles

Phosphorylation of MtRopGEF2 by LYK3 mediates MtROP activity to regulate rhizobial infection in Medicago truncatula

Mingxing Wang1,2,3†, Huan Feng2,4†, Peng Xu2,5, Qiujin Xie2,3, Jinpeng Gao2,3, Yanzhang Wang2, Xiaowei Zhang2, Jun Yang2, Jeremy D. Murray2, Fengli Sun5, Chunyan Wang4, Ertao Wang2* and Nan Yu1*   

  1. 1 College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
    2 National key Laboratory of Plant Molecular Genetics, Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, the Chinese Academy of Sciences, Shanghai 200032, China
    3 University of Chinese Academy of Sciences, Beijing 100039, China
    4 College of Forestry, Northwest A&F University, Yangling 712100, China
    5 College of Agronomy, Northwest A&F University, Yangling 712100, China

    These authors contributed equally to this article.
    *Correspondences: Ertao Wang (etwang@cemps.ac.cn); Nan Yu (nyu@shnu.edu.cn, Dr. Yu is responsible for the distribution of the materials associated with this article)
  • Received:2021-03-13 Accepted:2021-07-05 Online:2021-07-08 Published:2021-10-01

Abstract: The formation of nitrogen-fixing no dules on legume roots requires the coordination of infection by rhizobia at the root epidermis with the initiation of cell divisions in the root cortex. During infection, rhizobia attach to the tip of elongating root hairs which then curl to entrap the rhizobia. However, the mechanism of root hair deformation and curling in response to symbiotic signals is still elusive. Here, we found that small GTPases (MtRac1/MtROP9 and its homologs) are required for root hair development and rhizobial infection in Medicago truncatula. Our results show that the Nod factor receptor LYK3 phosphorylates the guanine nucleotide exchange factor MtRopGEF2 at S73 which is critical for the polar growth of root hairs. In turn, phosphorylated MtRopGEF2 can activate MtRac1. Activated MtRac1 was found to localize at the tips of root hairs and to strongly interact with LYK3 and NFP. Taken together, our results support the hypothesis that MtRac1, LYK3, and NFP form a polarly localized receptor complex that regulates root hair deformation during rhizobial infection.

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