Thesis defense: Ekaterina Aleksenko
tress response
GNAT acetyltransferases
small amines
Arabidopsis
Friday, December 20th 2024, 1 pm, INRAE, Versailles
Small amines, associated proteins and stress responses in Arabidopsis
As sedentary organisms, plants face a multitude of unavoidable stresses, such as unfavorable soil composition, drought and heat stress as well as various biotic stresses. They have developed adaptation strategies, based on myriads of proteins and metabolites that interact in complex networks to allow the plant to respond appropriately according to the nature and strength of the stresses. One such protein is the NATA1 acetyltransferase and its product, a small acetylated diamine (acetyl-1,3-diaminopropane, acDAP) involved in drought stress, aiding in balancing conflicting needs for water conservation and CO2 uptake by counteracting stomatal closure mediated by abssicis acid (ABA). NATA1 along with its’ close homolog of unknown function NATA2, as well as a potential downstream actor of acetyl-DAP, have been the focus of this study. NATA1 and NATA2 belong to the large Gcn5-Related N-Acetyltransferase (GNAT) superfamily, that has hundreds of thousands of members acting on a variety of substrates from proteins to small amines, thus participating in various crucial developmental, metabolic and stress response processes. Found in tandem in the genome, the two NATA protein are believed to have originated from a gene duplication event and despite their nearly 80% identity and conservation of the catalytic domain, they evolved to have a different substrate selectivity. Thus, the first question this study addressed was “How do NATA1 and NATA2 achieve different substrate selectivities despite their high similarity?” leading to a broader question of “How does GNAT structure drive substrate selectivity for small amine substrates?”. Modeling, mutagenesis and enzymatic assays provided insight into how NATA1 and NATA2 interact with their substrates and identified key differences between the enzymes. However, NATA1 has not only diverged from NATA2 in its’ enzymatic activity, but, also in its’ expression pattern and, likely, its’ roles in planta. The second and third questions of this study were “How do NATA1 and NATA2 expression patterns differ in response to stress conditions?” and “What are the potential roles of NATA2?”. Finally, a modified yeast-two hybrid assay identified a potential acetyl-DAP binding protein (DBP), providing the opportunity to question potential downstream events and targets of acDAP and address the last question of “What is the functional role of this new actor associated with small amine metabolism by exploiting CRISPR-generated dbp mutants.
Director: Valérie Gaudin - INRAE, IJPB, Versailles, équipe
Members of the jury
> Alexandre Berr (rapporteur) - CNRS, IBMP, Strasbourg
> Philippe Nacry (rapporteur) - INRAE, IPSiM, Montpellier
> Catherine Bellini (rapportrice) - INRAE, IJPB, Versailles
> Mariane Delarue (Examinatrice) - Université Paris-Saclay, IPS2, Gif-sur-Yvette
> Jeffrey Leung (invité)- CNRS, INRAE, IJPB, Versailles
To attend, contact Valérie Gaudin
Research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.
As sedentary organisms, plants face a multitude of unavoidable stresses, such as unfavorable soil composition, drought and heat stress as well as various biotic stresses. They have developed adaptation strategies, based on myriads of proteins and metabolites that interact in complex networks to allow the plant to respond appropriately according to the nature and strength of the stresses. One such protein is the NATA1 acetyltransferase and its product, a small acetylated diamine (acetyl-1,3-diaminopropane, acDAP) involved in drought stress, aiding in balancing conflicting needs for water conservation and CO2 uptake by counteracting stomatal closure mediated by abssicis acid (ABA). NATA1 along with its’ close homolog of unknown function NATA2, as well as a potential downstream actor of acetyl-DAP, have been the focus of this study. NATA1 and NATA2 belong to the large Gcn5-Related N-Acetyltransferase (GNAT) superfamily, that has hundreds of thousands of members acting on a variety of substrates from proteins to small amines, thus participating in various crucial developmental, metabolic and stress response processes. Found in tandem in the genome, the two NATA protein are believed to have originated from a gene duplication event and despite their nearly 80% identity and conservation of the catalytic domain, they evolved to have a different substrate selectivity. Thus, the first question this study addressed was “How do NATA1 and NATA2 achieve different substrate selectivities despite their high similarity?” leading to a broader question of “How does GNAT structure drive substrate selectivity for small amine substrates?”. Modeling, mutagenesis and enzymatic assays provided insight into how NATA1 and NATA2 interact with their substrates and identified key differences between the enzymes. However, NATA1 has not only diverged from NATA2 in its’ enzymatic activity, but, also in its’ expression pattern and, likely, its’ roles in planta. The second and third questions of this study were “How do NATA1 and NATA2 expression patterns differ in response to stress conditions?” and “What are the potential roles of NATA2?”. Finally, a modified yeast-two hybrid assay identified a potential acetyl-DAP binding protein (DBP), providing the opportunity to question potential downstream events and targets of acDAP and address the last question of “What is the functional role of this new actor associated with small amine metabolism by exploiting CRISPR-generated dbp mutants.
Director: Valérie Gaudin - INRAE, IJPB, Versailles, équipe
Members of the jury
> Alexandre Berr (rapporteur) - CNRS, IBMP, Strasbourg
> Philippe Nacry (rapporteur) - INRAE, IPSiM, Montpellier
> Catherine Bellini (rapportrice) - INRAE, IJPB, Versailles
> Mariane Delarue (Examinatrice) - Université Paris-Saclay, IPS2, Gif-sur-Yvette
> Jeffrey Leung (invité)- CNRS, INRAE, IJPB, Versailles
To attend, contact Valérie Gaudin
Research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.
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