Redox regulation of glutenin subunit assembly in the plant endoplasmic reticulum

Authors

  • Alessio Lombardi,

    1. Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche, Milano, Italy
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    • These authors contributed equally to this work.

  • Richard S. Marshall,

    1. Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche, Milano, Italy
    Current affiliation:
    1. Department of Genetics, University of Wisconsin, Madison, WI, USA
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    • These authors contributed equally to this work.

  • Chiara L. Castellazzi,

    1. Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche, Milano, Italy
    Current affiliation:
    1. Departamento de Biologia Estructural y Computacional, Instituto de Investigación Biomédica, Barcelona, Spain
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  • Aldo Ceriotti

    Corresponding author
    • Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche, Milano, Italy
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(e-mail ceriotti@ibba.cnr.it).

Summary

The glutenin fraction of wheat storage proteins consists of large polymers in which high- and low-molecular-weight subunits are connected by inter-chain disulfide bonds. We found that assembly of a low-molecular-weight glutenin subunit in the endoplasmic reticulum is a rapid process that leads to accumulation of various oligomeric forms, and that this assembly is sensitive to perturbation of the cellular redox environment. In endoplasmic reticulum-derived microsomes, low-molecular-weight glutenin subunits are subjected to hyper-polymerization, indicating that cytosolic factors play an important role in limiting polymer size. Addition of physiological concentrations of reduced glutathione is sufficient to maintain the original polymerization pattern of the glutenin subunits upon cytosol dilution. Furthermore, we show that a low-molecular-weight glutenin subunit can be glutathionylated in endoplasmic reticulum-derived microsomes, and that it can be directly reduced by glutathione in vitro. These results indicate that glutenin polymerization is sensitive to changes in the redox state of the cell, and suggest that the presence of a reducing cytosolic environment plays an important role in regulating disulfide bond formation in the endoplasmic reticulum of plant cells.

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