Research Christa Testerink
Research interest
Plants have the ability to quickly and adequately react to sudden changes in their environment. One of the first reactions is to change the composition of the lipids in the cell membrane. This in turn triggers a cascade of intracellular signaling that eventually leads to acclimatization and survival. A key player in the response of plants to many stress conditions is the lipid second messenger phosphatidic acid (PA). My main research interest is to elucidate how phosphatidic acid modulates protein function and downstream plant responses.
Recently, we have started to focus on how lipid signaling affects stress-induced changes in root system architecture and growth of Arabidopsis.
Ongoing research
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PA targets
Phosphatidic acid (PA) has recently been identified as a lipid second messenger in eukaryotes. In plants, it is typically produced upon several biotic and abiotic stimuli and functions as a docking site for proteins. Using a proteomics approach involving purification on PA-beads followed by mass spectrometry, we identified a set of proteins that have affinity for PA.
Several of these were protein kinases and phosphatases, implicated in various plant physiological responses. At the moment, we are investigating one of these targets, a Snf-1 related protein kinase (SnRK2), which is activated upon exposure of the plant to osmotic stress.
Function of PA targets
We study the role of PA and its targets in the response of plants to osmotic stress. PA-binding protein kinases and phosphatases implicated in these responses are further characterized with the aim to elucidate the mode of action of PA in affecting protein function and to understand how PA regulation of proteins affects downstream responses.
NWO-ALW project
One of the responses to salinity stress is re-direction of root growth, most likely via modulation of auxin transport. In our group, Carlos Galvan is studying the molecular and cellular mechanism behind this phenomenon.
Figure above adapted from Galvan-Ampudia and Testerink, COPB 2011
Learning from nature
Besides using mutants, we also investigate natural variation between Arabidopsis accessions, with the aim to identify novel loci contributing to optimal root growth in the presence of salinity or osmotic stress.
see also Magdalena Julkowska's website
New PA targets
A differential proteomics screen has been set up to isolate PA-binding candidate proteins that are targeted to the membrane in response to a PA increase. For this purpose, we isolate peripheral membrane proteins of control cells vs. stimulated cells and select PA-binding proteins that are only present in the stimulated sample. In this way, a novel set of PA targets has been identified by mass spectrometry.
see also Fionn McLoughlin's website
Molecular basis of PA-binding
Vidi/I2CAM project
We have analyzed the PA-binding sites of the Arabidopsis protein kinases CTR1, SnRK2 and PDK1. Elucidation of the molecular basis of PA-binding will allow us to manipulate PA-binding ability of these and other protein kinases. As such, it will help us establish the function of PA-binding in downstream responses of plants to stress.
Manipulation of PA levels in plants
NGI-Horizonproject
A chemical emergency switch for plants
Plants have the ability to quickly and adequately react to adverse conditions, such as pathogens, drought and high salinity of the soil. One of the first reactions isto change the composition of the lipids in the cell membrane. This in turn triggers a cascade of intracellular signaling that eventually leads to acclimatization and survival. A key player in the response of plants to many stress conditions is the membrane-localized signal phosphatidic acid (PA).
The aim of this project is to control the production of PA and identify its proteome-wide downstream effects. We will engineer a chemical switch, which will allow synthesis of PA on demand. We will then turn on the switch and investigate the proteome-wide consequences. Finding the key players in the response to the emergency signal PA will increase our understanding of plant stress signalling and will aid in defining new strategies for generating more stress-resistant crops.
The project builds on the group's extensive expertise in investigating lipid signaling in plant cells, integrating molecular technologies and proteomics with cell biology. We will combine (i) molecular cloning of membrane-targetable lipid-modifying enzymes for expression in cultured plant cells and roots, with (ii) proteomics and confocal microscopy approaches to investigate downstream cellular consequences.
Student's projects
There are always possibilities for students to do an internship in our group. Please enquire for specific projects currently available.
Depending on the length of the practical training period (minimum 4 months), the student can work on several different subprojects, focussed on understanding salt tolerance of plants, hormonal regulation, protein-lipid interactions and/or ecogenomics of root architecture. Each of the projects will involve a diverse array of techniques, including: protein expression and purification, protein kinase assays, lipid binding assays, confocal microscopy, plant physiological assays using mutants and naturally adapted accessions of Arabidopsis, Q-RT-PCR, cloning and plant transformation.
Section of Plant Physiology
I work within the Plant Physiology group headed by Prof. dr. Michel Haring. Other staff members are Dr. Rob Schuurink (volatile signaling) and Dr. Teun Munnik (phospholipid signaling).
Website Plant Cluster SILS
SILS research groups
Abstract NWO-CW Vidi grant
Modulation of protein kinase function by the lipid second messenger phosphatidic acid
First picture in our new lab (2009)
Visiting address:
Room C2.211
Science Park 904
1098 XH Amsterdam