HOP family plays a major role in long‐term acquired thermotolerance in Arabidopsis

• Published in: Plant, cell and environment cell and environment, 2018-08, Vol.41 (8), p.1852-1869
• Main Authors: Fernández‐Bautista, Nuria, Fernández‐Calvino, Lourdes, Muñoz, Alfonso, Toribio, René, Mock, Hans P., Castellano, M. Mar
• Format: Article
• Language: English
• Subjects: Acclimation; Acclimatization; Arabidopsis; Arabidopsis - physiology; Arabidopsis Proteins - physiology; Attenuation; Blotting, Western; cochaperone; Cytoplasm; Eukaryotes; Gene Expression Regulation, Plant; Glucuronidase - metabolism; Heat; High temperature; Hsp70 protein; HSP70‐HSP90 organizing protein; HSP90; Hsp90 protein; LAT; Molecular chains; Molecular Chaperones - physiology; Nuclei; plants; Polymerase Chain Reaction; Proteins; Quality control; Sequence Analysis, RNA; Thermotolerance; Transcription
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13326

HSP70‐HSP90 organizing protein (HOP) is a family of cytosolic cochaperones whose molecular role in thermotolerance is quite unknown in eukaryotes and unexplored in plants. In this article, we describe that the three members of the AtHOP family display a different induction pattern under heat, being HOP3 highly regulated during the challenge and the attenuation period. Despite HOP3 is the most heat‐regulated member, the analysis of the hop1 hop2 hop3 triple mutant demonstrates that the three HOP proteins act redundantly to promote long‐term acquired thermotolerance in Arabidopsis. HOPs interact strongly with HSP90 and part of the bulk of HOPs shuttles from the cytoplasm to the nuclei and to cytoplasmic foci during the challenge. RNAseq analyses demonstrate that, although the expression of the Hsf targets is not generally affected, the transcriptional response to heat is drastically altered during the acclimation period in the hop1 hop2 hop3 triple mutant. This mutant also displays an unusual high accumulation of insoluble and ubiquitinated proteins under heat, which highlights the additional role of HOP in protein quality control. These data reveal that HOP family is involved in different aspects of the response to heat, affecting the plant capacity to acclimate to high temperatures for long periods. Heat is one of the environmental stresses that most drastically impact on plant growth, development and yield. This article describes for the first time that HOPs (HSP70‐1152 HSP90 organizing proteins) play a main role in long term acquired thermotolerance, affecting different aspects of this complex response