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Doctoral thesis, 2022

Living through hard times: Dispose of or sequester? Plant subcellular strategies for stress resilience

Elander, Pernilla;

Abstract

Extreme weather events have become the new normal due to climate change and global warming. This damages crop harvests, threatening global food production. One of the many measures to ensure food security is to develop stress-resilient plants, but to do that we need to understand how plants respond to stress factors. In this work, we studied two cellular mechanisms underlying plant resilience, autophagy and formation of stress granules (SGs). Autophagy is an evolutionarily conserved vesicle trafficking pathway which at the time of stress disposes of cellular constituents which might be superfluous, hazardous or dysfunctional by degrading them in the lysosome (animals) or vacuole (fungi and plants). In our studies we have focused on autophagy-related proteins ATG5 and ATG7, the core components of the ATG8 and ATG5-12 conjugation systems. Overexpression of ATG5 or ATG7 led to increased lipidation of ATG8 and enhanced autophagic recycling without affecting the transcription level of other components of the conjugation systems, indicating that ATG5 and ATG7 are ratelimiting steps of the autophagy pathway. Plants with enhanced levels of either ATG5 or ATG7 showed improved fitness for a broad range of agronomically important traits, such as, increased vegetative biomass, delayed senescence and increased seed set. Surprisingly, these plants also displayed improved tolerance to necrotrophic pathogens and oxidative stress. Our findings can be used for growing resilient crops with improved productivity. A follow up study addressed the roles of ATG5 unrelated to autophagy, by isolating interactomes of the wild-type ATG5 and its point mutant which does not conjugate to ATG12. LC-MS/MS analysis yielded 104 interactor hits for the wild-type ATG5, 78 for the mutant and 97 hits shared by the wild-type and the mutant. Further functional studies are required to understand the roles of ATG5 and its interactors of autophagy-unrelated pathways in plants. SGs are membraneless protein-mRNA biomolecular condensates formed via phase separation under stress, which selectively sequester or concentrate proteins and mRNAs. The sequestration of proteins can result in activation or suppression of biochemical pathways. We investigated the interactome of the Tudor staphylococcal nuclease (TSN) protein. TSN is a multifunctional and evolutionary conserved regulator of gene expression, previously shown to stably associate with SGs under heat stress. We found that TSN functions as a docking platform for SG components and its localization to SGs is essential for the activation of a major regulator of energy homeostasis in the cell, SnRK1 (a homolog of AMPK/SNF1). Our work provides a proteome-wide resource of SG components and sheds light on the signalling role of stress granules in plant physiology.

Keywords

recycling; degradation; stress response; biomolecular condensates; autophagy; stress granules; plant resilience; plant stress; climate change; återvinning; nedbrytning; stressrespons; biomolekylära kondensat; autofagi; stressgranuler; växters motståndskraft; växtstress; klimatförändringar

Published in

Acta Universitatis Agriculturae Sueciae

2022, number: 2022:60
ISBN: 978-91-7760-995-7, eISBN: 978-91-7760-996-4
Publisher: Swedish University of Agricultural Sciences

Authors' information

Swedish University of Agricultural Sciences, Department of Molecular Sciences

UKÄ Subject classification

Agricultural Science

URI (permanent link to this page)

https://res.slu.se/id/publ/119473