, Volume 246, Issue 1, pp 75–89 | Cite as

In Brachypodium a complex signaling is actuated to protect cells from proteotoxic stress and facilitate seed filling

  • Sang-Jin Kim
  • Starla Zemelis-Durfee
  • Curtis Wilkerson
  • Federica Brandizzi
Original Article


Main conclusion

A conserved UPR machinery is required for Brachypodium ER stress resistance and grain filling.

Human and livestock diets depend on the accumulation of cereal storage proteins and carbohydrates, including mixed-linkage glucan (MLG), in the endosperm during seed development. Storage proteins and proteins responsible for the production of carbohydrates are synthesized in the endoplasmic reticulum (ER). Unfavorable conditions during growth that hamper the ER biosynthetic capacity, such as heat, can cause a potentially lethal condition known as ER stress, which activates the unfolded protein response (UPR), a signaling response designed to mitigate ER stress. The UPR relies primarily on a conserved ER-associated kinase and ribonuclease, IRE1, which splices the mRNA of a transcription factor (TF), such as bZIP60 in plants, to produce an active TF that controls the expression of ER resident chaperones. Here, we investigated activation of the UPR in Brachypodium, as a model to study the UPR in seeds of a monocotyledon species, as well as the consequences of heat stress on MLG deposition in seeds. We identified a Brachypodium bZIP60 orthologue and determined a positive correlation between bZIP60 splicing and ER stress induced by chemicals and heat. Each stress condition led to transcriptional modulation of several BiP genes, supporting the existence of condition-specific BiP regulation. Finally, we found that the UPR is elevated at the early stage of seed development and that MLG production is negatively affected by heat stress via modulation of MLG synthase accumulation. We propose that successful accomplishment of seed filling is strongly correlated with the ability of the plant to sustain ER stress via the UPR.


bZIP60 Endosperm ER stress Heat stress Mixed-linkage glucan 



Mixed-linkage glucan


Unfolded protein response


Regulated Ire1-dependent decay



We are grateful to Dr. Monika Doblin (University of Melbourne) for providing the anti-CSLF6 serum. This study was primarily supported by DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-FC02-07ER64494), with contributing support from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy (award number DE-FG02-91ER20021) for infrastructure, National Institutes of Health (GM101038), and AgBioResearch.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

425_2017_2687_MOESM1_ESM.pdf (197 kb)
Supplementary material 1 (PDF 197 kb)
425_2017_2687_MOESM2_ESM.pdf (159 kb)
Supplementary material 2 (PDF 159 kb)
425_2017_2687_MOESM3_ESM.pdf (25 kb)
Supplementary material 3 (PDF 25 kb)
425_2017_2687_MOESM4_ESM.pdf (9 kb)
Supplementary material 4 (PDF 8 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Great Lakes Bioenergy Research CenterMichigan State UniversityEast LansingUSA
  2. 2.MSU-DOE Plant Research LabMichigan State UniversityEast LansingUSA
  3. 3.Department of Plant BiologyMichigan State UniversityEast LansingUSA

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