Understanding the role of redox modifications during mitochondrial signaling
(2025) MOBN03 20242Degree Projects in Molecular Biology
- Abstract
- Mitochondria are most known as producers of ATP and for their metabolic functions in eukaryotic cells. However, these are not the only roles of these organelles, as they also have the means to communicate with the nucleus. These signals going from mitochondria to the cell nucleus are termed mitochondrial retrograde signaling or regulation (MRR). In Arabidopsis thaliana, the master regulator of MRR is the ER-embedded transcription factor ANAC017. Upon mitochondrial dysfunction, ANAC017 is thought to be proteolytically cleaved by intramembrane rhomboid-like proteases (RBLs) from the ER membrane and translocated to the nucleus. Once inside the nucleus, ANAC017 acts as a transcription factor to facilitate expression of genes involved in stress... (More)
- Mitochondria are most known as producers of ATP and for their metabolic functions in eukaryotic cells. However, these are not the only roles of these organelles, as they also have the means to communicate with the nucleus. These signals going from mitochondria to the cell nucleus are termed mitochondrial retrograde signaling or regulation (MRR). In Arabidopsis thaliana, the master regulator of MRR is the ER-embedded transcription factor ANAC017. Upon mitochondrial dysfunction, ANAC017 is thought to be proteolytically cleaved by intramembrane rhomboid-like proteases (RBLs) from the ER membrane and translocated to the nucleus. Once inside the nucleus, ANAC017 acts as a transcription factor to facilitate expression of genes involved in stress response. Since the recent finding that mitochondrial ROS are the likely trigger for ANAC017 activation, it has been hypothesized that during stress, Cys536 in the transmembrane domain (TMD) of ANAC017 is oxidized. This could destabilise the conformation of ANAC017 TMD helix and make it susceptible to cleavage by RBLs for subsequent translocation to the nucleus. This project aimed to investigate this by analysing different versions of ANAC017 with mutations around the mentioned Cys536 residue. Furthermore, we aimed to investigate potential involvement of ANAC017-mediated MRR signaling during hypoxia and UV stress. Finally, we also explored involvement of selected RBLs in ANAC017 signaling. For this purpose, we used methods such as cloning, transgenic plant generation, gene expression analysis, phenotypic analysis and confocal microscopy. We found that complementation of anac017 mutants is not trivial, and while we elucidated the effect of ANAC017 TMD mutations to a certain extent, more research needs to be done in the future. We found a measurable but limited role of ANAC017 in hypoxia stress. Furthermore, RBLs we tested, showed no clear role in ANAC017 signaling, neither during hypoxia nor mitochondrial inhibitor treatment, leading us to question the role of RBLs in ANAC017 activation. Finally, we showcase that ANAC017 is a regulator of UV responses in plants. (Less)
- Popular Abstract
- Role of redox modifications in mitochondrial signaling in plants
Plants are sessile organisms that need to constantly adapt to the ever-changing environment around them to grow and survive. To achieve this, plants sense their environment in many different ways. Zooming in to the cellular level, the organelles of plant cells, mitochondria and chloroplasts both have a role in this sensing of the environment. For their optimal functioning in their central energetic roles, these organelles rely on the nucleus to orchestrate cellular homeostasis. In turn, the nucleus relies on the organelles to provide it with feedback. This feedback signal, coming from the organelles, is termed mitochondrial retrograde signaling.
or regulation (MRR). In... (More) - Role of redox modifications in mitochondrial signaling in plants
Plants are sessile organisms that need to constantly adapt to the ever-changing environment around them to grow and survive. To achieve this, plants sense their environment in many different ways. Zooming in to the cellular level, the organelles of plant cells, mitochondria and chloroplasts both have a role in this sensing of the environment. For their optimal functioning in their central energetic roles, these organelles rely on the nucleus to orchestrate cellular homeostasis. In turn, the nucleus relies on the organelles to provide it with feedback. This feedback signal, coming from the organelles, is termed mitochondrial retrograde signaling.
or regulation (MRR). In Arabidopsis thaliana, the model plant organism we are working on, the master regulator of MRR is a protein called ANAC017. Upon stress induction, ANAC017 is cleaved and released from the ER membrane and translocated to the nucleus, where it acts as a transcription factor to facilitate expression of genes involved in the stress response.
The aim of this project was to elucidate by what mechanisms ANAC017 is released from the ER activated during stress. It is hypothesized that during stress, specific amino acids of ANAC017 are oxidized by highly reactive oxygen species (ROS) leaking from inhibited mitochondria, making the protein susceptible to cleavage and translocation to the nucleus. To examine this hypothesis, transgenic plants with different mutated versions of ANAC017 were created and the functionality of their MRR and ANAC017 was tested using gene expression analysis, phenotypic analysis and confocal microscopy. Our analysis showed a complex behaviour of the specific mutant forms, so further work is needed to make final conclusions. We also investigated the rhomboid-like intramembrane proteases previously suggested to cleave ANAC017, but our experiments could not confirm this role. Finally, we explored the activation of ANAC017 during hypoxia and UV stress, finding that ANAC017 that ANAC017 is an important regulator during these stresses.
Master’s Degree Project in Molecular Biology, 60 credits 2025
Department of Biology, Lund University
Supervisors: Olivier Van Aken & Kasim Khan
Advisors The Section of Molecular Biosciences, Department of Biology (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9214979
- author
- Draganja, Toma
- supervisor
-
- Olivier Van Aken LU
- Kasim Khan LU
- organization
- course
- MOBN03 20242
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9214979
- date added to LUP
- 2025-11-06 09:32:18
- date last changed
- 2025-11-06 09:32:18
@misc{9214979,
abstract = {{Mitochondria are most known as producers of ATP and for their metabolic functions in eukaryotic cells. However, these are not the only roles of these organelles, as they also have the means to communicate with the nucleus. These signals going from mitochondria to the cell nucleus are termed mitochondrial retrograde signaling or regulation (MRR). In Arabidopsis thaliana, the master regulator of MRR is the ER-embedded transcription factor ANAC017. Upon mitochondrial dysfunction, ANAC017 is thought to be proteolytically cleaved by intramembrane rhomboid-like proteases (RBLs) from the ER membrane and translocated to the nucleus. Once inside the nucleus, ANAC017 acts as a transcription factor to facilitate expression of genes involved in stress response. Since the recent finding that mitochondrial ROS are the likely trigger for ANAC017 activation, it has been hypothesized that during stress, Cys536 in the transmembrane domain (TMD) of ANAC017 is oxidized. This could destabilise the conformation of ANAC017 TMD helix and make it susceptible to cleavage by RBLs for subsequent translocation to the nucleus. This project aimed to investigate this by analysing different versions of ANAC017 with mutations around the mentioned Cys536 residue. Furthermore, we aimed to investigate potential involvement of ANAC017-mediated MRR signaling during hypoxia and UV stress. Finally, we also explored involvement of selected RBLs in ANAC017 signaling. For this purpose, we used methods such as cloning, transgenic plant generation, gene expression analysis, phenotypic analysis and confocal microscopy. We found that complementation of anac017 mutants is not trivial, and while we elucidated the effect of ANAC017 TMD mutations to a certain extent, more research needs to be done in the future. We found a measurable but limited role of ANAC017 in hypoxia stress. Furthermore, RBLs we tested, showed no clear role in ANAC017 signaling, neither during hypoxia nor mitochondrial inhibitor treatment, leading us to question the role of RBLs in ANAC017 activation. Finally, we showcase that ANAC017 is a regulator of UV responses in plants.}},
author = {{Draganja, Toma}},
language = {{eng}},
note = {{Student Paper}},
title = {{Understanding the role of redox modifications during mitochondrial signaling}},
year = {{2025}},
}