Dissecting Arabidopsis phospholipid signaling using reverse genetics

Living cells delimit themselves from their surroundings by a biological membrane.
This biological membrane is essential to maintain chemical gradients between the
intracellular and extracellular environment and leakage would quickly be followed
by death. The structural integrity of the membrane is the result of the biophysical
properties of its primary building blocks, the phospholipids. Phospholipids have
two hydrophobic fatty acid tails and a hydrophilic headgroup, held together by a
simple glyceryl backbone. When in acqueous solution, phospholipids spontaneously
form a bilayer with their hydrophobic tails facing each other and their hydrophilic
headgroups forming hydrogen bonds with the water molecules in the solution. The
result is a barrier that is impermeable to large and charged molecules. In addition to
preventing molecules to leave or enter, the membrane is also involved in
communication between the outside world and the inside of the cell. These two
functions are reflected by the composition of the lipid bilayer. The majority of the
phospholipids have a structural role and their concentrations are relatively constant.
However, a minority of the phospholipids rapidly turn over in response to various
external stimuli. In mammals, the role of phospholipids in intracellular signaling is
well described. For plants, evidence for such roles is emerging, although differences
are also found. Plant phospholipid signaling is the subject of my thesis. In the first
two sections of the general introduction, phospholipid biosynthesis will be
described, as well as the different species of phospholipids and their mode of action.
In the third section we will focus on the available techniques to study plant
phospholipid signaling and our model organism, Arabidopsis thaliana will be
introduced. In the final sections of this introduction, an overview will be given of
several biological processes that have been associated with phospholipid signaling.
These sections form a bridge to the four experimental chapters of this thesis. In the
last chapter, selected findings are discussed within a broader context.