One of the most striking aspects of plant life is the evolved ability to cope with continuous changes in environmental conditions. Drought, soil salinity and temperature extremes impose severe stresses to which plants respond with changes in metabolism and development. Resilience in the face of environmental challenges is essential for survival in wide-ranging environments. Lipids, which form the structural basis of all membranes play key roles under stress conditions, making up the structures and regulating the functions of membranes, fine-tuning metabolic balance, and acting as cellular signals. Through such diverse functions, lipids help plants to cope with environmental stress .
An important class of molecules that coordinate stress responses at the cellular level are specialized membrane lipids such as phosphoinositides and phosphatidic acids (PA). The formation of these lipids is rapidly triggered upon perception of the stress condition and they are believed to act as cellular signals to regulate the stress response. However, it is generally not well understood how they function.
One emerging paradigm is that they act by binding to specific proteins which are thus altered in subcellular localization and/or activity. Aided by advances in mass spectrometry-based proteomics, an increasing number of protein targets have been discovered in plants, including protein kinases and phosphatases, transcription factors, cytoskeletal elements and metabolic enzymes. How lipid-protein interactions, in conjunction with other signaling pathways, regulate physiological responses to generate stress-tolerance, has become a central topic in plant science, and one of my major research interests .
When plants experience a period of cold (0°C-8°C), they can become more tolerant to freezing. This phenomenon, commonly known as cold acclimation, involves extensive changes in the plant, ranging from accumulations of sugars and antifreeze proteins to adjustments in growth and development. Cold acclimation is essential to survival at temperate latitudes and as such has been a long-studied subject in basic plant physiology. Membranes are important in this process since they are particularly vulnerable cellular structures when freezing occurs. Their integrity is jeopardized by the formation of ice crystals and the loss of liquid water from cells which causes severe dehydration. Little is known however about the mechanisms that confer resilience to plant membranes under such adverse conditions.
Recently, we identified a novel component of freezing tolerance in the wild Arabidopsis relative Boechera stricta which lives in diverse habitats at high altitudes of the Rocky Mountains . From quantitative trait locus analysis of seedling freezing stress tolerance, a locus emerged containing the gene encoding Acyl-CoA:Diacylglycerol Acyltransferase 1 (DGAT1), a well-studied enzyme known to be responsible for seed oil biosynthesis. At freezing temperatures the enzyme was shown to produce oil (triacylglycerol) in leaves and to confer tolerance. Comprehensive analysis of lipids suggested that in the same process also sugar-rich lipids (oligogalactosyl-diacylglycerols) were formed which had previously been found to stabilize chloroplast membranes. Consistently with the proposed function for DGAT1 under freezing conditions, Arabidopsis plants overexpressing DGAT1 showed greater survival of freezing.
In light of our discovery of DGAT1 as determinant of freezing tolerance, it will be interesting to further investigate how DGAT1 activity is regulated at low temperatures and how it imparts tolerance to plants.
These questions are subject of my current research at the Munnik lab/ Plant Cell Biology.
 Hou et al. (2016) Plant Cell Env 39, 1029–1048
 McLoughlin et al. (2013) Biochem J 450, 573-581
 Arisz et al. (2018) Plant Physiol 177, 1410-1424 http://www.plantphysiol.org/content/early/2018/06/15/pp.18.00503
Steven Arisz works as senior postdoctoral researcher at the University of Amsterdam (NL) research group Plant Cell Biology (Swammerdam Institute for Life Sciences). He has studied biology at the UvA (1990-1996, cum laude) and continued as PhD-student in plant physiology, studying lipid metabolism in abiotic stress signaling of green algae and plants. This resulted in a dissertation entitled “Plant Phosphatidic Acid Metabolism in Response to Environmental Stress” (2010). After this, he did a postdoc at the lab of prof. Christa Testerink studying, among other things, lipid-protein interactions in response to salt stress (2011-2018). As of 2018, he continued as senior postdoc in the lab of dr. Teun Munnik (Plant Cell Biology, UvA). In collaboration with prof. Eric Schranz (Biosystematics group, Wageningen University), dr. Jae-Yun Heo (Gangneung-Wonju National University, Korea) and prof. Tom Mitchell-Olds (Duke University, Durham, US), he is conducting a research project on natural variation in freezing tolerance of Boechera stricta. Steven has given presentations at international symposia, is lead author of well-cited research and review articles and several book chapters, and functions frequently as peer reviewer for leading scientific journals in plant science. Moreover, he enjoys teaching and helping students. Apart from his scientific work, Steven contributes to raising awareness of inclusiveness and accessibility for people with disabilities at the university.