title: In Brachypodium a complex signaling is actuated to protect cells from proteotoxic stress and facilitate seed filling.
abstract: 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.
authors.affiliation: Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Sang-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Starla
authors.initials: S
authors.lastname: Zemelis-Durfee
authors.affiliation: Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, 48824, USA.|Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Curtis
authors.initials: C
authors.lastname: Wilkerson
authors.affiliation: Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, 48824, USA. fb@msu.edu.|MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, 48824, USA. fb@msu.edu.|Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA. fb@msu.edu.
authors.forename: Federica
authors.identifier: http://orcid.org/0000-0003-0580-8888
authors.initials: F
authors.lastname: Brandizzi
mesh_terms: D058431:Brachypodium / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D059865:Endoplasmic Reticulum Stress / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D006358:Hot Temperature; D012326:RNA Splicing / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D056811:Unfolded Protein Response / Q000235:genetics / Q000502:physiology
chemical_list: D014157:Transcription Factors
keywords: ER stress; Endosperm; Heat stress; Mixed-linkage glucan; bZIP60