Abstract
ABSTRACT In nature, plants are constantly exposed to many transient, but recurring, stresses. Thus, to complete their life cycles, plants require a dynamic balance between capacities to recover following cessation of stress and maintenance of stress memory. Recently, we uncovered a new functional role for macroautophagy/autophagy in regulating recovery from heat stress (HS) and resetting cellular memory of HS in Arabidopsis thaliana. Here, we demonstrated that NBR1 (next to BRCA1 gene 1) plays a crucial role as a receptor for selective autophagy during recovery from HS. Immunoblot analysis and confocal microscopy revealed that levels of the NBR1 protein, NBR1-labeled puncta, and NBR1 activity are all higher during the HS recovery phase than before. Co-immunoprecipitation analysis of proteins interacting with NBR1 and comparative proteomic analysis of an nbr1-null mutant and wild-type plants identified 58 proteins as potential novel targets of NBR1. Cellular, biochemical and functional genetic studies confirmed that NBR1 interacts with HSP90.1 (heat shock protein 90.1) and ROF1 (rotamase FKBP 1), a member of the FKBP family, and mediates their degradation by autophagy, which represses the response to HS by attenuating the expression of HSP genes regulated by the HSFA2 transcription factor. Accordingly, loss-of-function mutation of NBR1 resulted in a stronger HS memory phenotype. Together, our results provide new insights into the mechanistic principles by which autophagy regulates plant response to recurrent HS. Abbreviations: AIM: Atg8-interacting motif; ATG: autophagy-related; BiFC: bimolecular fluorescence complementation; ConA: concanamycinA; CoIP: co-immunoprecipitation; DMSO: dimethyl sulfoxide; FKBP: FK506-binding protein; FBPASE: fructose 1,6-bisphosphatase; GFP: green fluorescent protein; HS: heat stress; HSF: heat shock factor; HSFA2: heat shock factor A2; HSP: heat shock protein; HSP90: heat shock protein 90; LC-MS/MS: Liquid chromatography-tandem mass spectrometry; 3-MA: 3-methyladenine; NBR1: next-to-BRCA1; PQC: protein quality control; RFP: red fluorescent protein; ROF1: rotamase FKBP1; TF: transcription factor; TUB: tubulin; UBA: ubiquitin-associated; YFP: yellow fluorescent protein
Highlights
Temperatures higher than taxa-specific thresholds are dama ging, and lethal if sufficiently severe, for all organisms
We demonstrate that NBR1 binds rotamase FKBP1 (ROF1) and heat shock protein 90 (HSP90).1, and mediates their degradation during the heat stress (HS) recovery phase, thereby repressing heat shock factor A2 (HSFA2) transcriptional activity, continuity of heat shock protein (HSP) synthesis, and the enhanced protection to potentially imminent HS
As expected, primed plants accumulated a significantly greater number of NBR1GFP puncta than untreated control plants at all three selected time points during the recovery phase, with a peak at day 2 (Figure 1B,C, S1A-D and Video S1). This increase confirmed that the delivery of NBR1 to the vacuole through autophagy is enhanced during the HS recovery phase
Summary
Temperatures higher than taxa-specific thresholds are dama ging, and lethal if sufficiently severe, for all organisms. Exposure to high sub-lethal temperature induces diverse responses that enhance a plant’s ability to maintain cellular homeostasis and survival during the stress [2,3,6,7,8]. In addition to immediate responses to HS, plants have evolved the ability to remember a previous HS exposure (HS mem ory), by maintaining some stress-related changes, thereby preparing them for a better response to future HS insults [9,10,11]. Responses to stresses are usually accom panied by reductions in growth [12]. To safe guard growth and reproduction in rapidly-changing envir onments, plants must delicately balance the degree of resetting following stress and maintenance of stress mem ory.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
