Cold Acclimation in Brachypodium distachyon
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Authors
Juurakko, Collin
Date
Type
thesis
Language
eng
Keyword
Brachypodium , Cold stress , Antifreeze proteins , Ice-binding proteins , Cold acclimation , Abiotic stress , Biotic stress
Alternative Title
Abstract
Freeze-thaw events, exacerbated by climate change and seasonal transition, together with the ubiquitous ice nucleation-active (INA+) phytopathogen, Pseudomonas syringae, can result in frost damage to crops. Certain cold-hardy plant species undergo cold acclimation (CA) to increase survival in sub-zero temperatures. Here, CA was explored using the freeze-tolerant model cereal, purple brome or Brachypodium distachyon, comprising investigations on the accumulation of compatible solutes, plasma membrane (PM) proteome changes, microbial community changes, and analyses of the products of the B. distachyon ice recrystallization inhibition genes (BdIRI) and their capacities to combat ice and P. syringae.
After CA, changes in PM-associated protein abundance were categorized as an early or a sustained response. By two days, plants showed reduced electrolyte leakage and freeze tolerance, regulated PM-associated proteins revealed extensive crosstalk between abiotic and biotic stress responses, and identified proteins offered new routes to engineer freeze-tolerant crops including chaperones, transporters, and receptors. CA also resulted in striking changes in the leaf microbiome with the INA+ P. syringae decreasing in relative abundance, coincident with an increase in the beneficial Streptomyces sp. M2. BdIRI products, though not identified in the PM proteome, are integral to the early CA response. Transgenic lines bearing a CA-induced rice promoter driving a miRNA that inhibited BdIRI translation showed no obvious developmental defects. However, transgenics displayed reduced antifreeze protein activity as assessed by IRI and thermal hysteresis along with increased electrolyte leakage, freeze susceptibility, and reduced INA+ attenuation compared to cold-acclimated wild type controls. Protein modelling suggested that antifreeze and leucine-rich repeat proteins of BdIRIs can dock to P. syringae ice nucleating proteins and the flagellin flg22 epitope, respectively. This suggests that BdIRIs not only protect against ice but have antipathogenic activities including the inhibition of ice nucleation and attenuation of energetically costly pattern-triggered immune responses during CA.
Overall, CA-orchestrated biochemical changes work collectively to provide not only tolerance to sub-zero temperatures but also INA+ phytopathogens. BdIRI gene products may thus be amongst the most promising for biotechnological innovation. These, and other proteins and pathways, comprise the integrated B. distachyon CA response and have inspired strategies for enhancing low temperature stress resistance in the future.
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This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 3.0 United States
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 3.0 United States