CELLGROWTH - RESEARCH
Plants are fascinating creatures. Their life is strikingly different from ours. The above-ground organs of plants are photosynthetic and therefore provide energy and oxygen to the rest of the life on Earth. On the other hand, plant roots live in soil where they anchor the plant, and provide it with water and nutrients. Plants developed a peculiar way of multicellularity: they build their bodies using a hydrostatic skeleton that consists of pressurized cells enclosed in strong but thin cell walls.
While animal development is ruled by cell movement and migration, plant cells are immobile, and all their spectacular shapes and patterns are sculptured by precise control of cell division and regulation of growth. Still, plants can move substantially to follow light, gravity, moisture, nutrients, and chemical gradients. Growth regulation underlies most of the movements of plants and their parts. This movie captures a pea plant while it is integrating gravity, light, and touch stimuli to grow upwards and find a suitable support using its tendrils:
However, the cellular growth control is most important in ontogenetic development of plants: formation of plant organs - roots, leaves and stems – requires dramatic increase of cell volumes during relatively short time. The Arabidopsis root tip represents a unique model system, where cells divide and then massively elongate in a narrow developmental window. The cell elongation propels the movement of the root tip through soil:
Cell growth is regulated by the phytohormone auxin: it stimulates elongation of above-ground organs and inhibits the elongation of root cells. This is exemplified during the gravitropic bending of the root, where auxin accumulates at the lower side of the root, cells inhibit their elongation and the root bends downwards:
These are a few examples by which we want to demonstrate that the regulation of cellular growth and elongation is of the essences of being a plant.
Even though cell growth is in the epicenter of plant development and reaction to environment, we understand very little how growth is controlled on the physiological and molecular level.
Using the example of the Arabidopsis root tip development, we want to understand how is the rapid cellular elongation triggered, coordinated and terminated. What are the protein networks that regulate these processes? How do the cells achieve the perfect coordination?
Auxin influences elongation of cells, but the mechanism of its action in the root is mostly unknown. We want to elucidate the molecular pathway from the perception of the hormone till the execution of the growth response. How is auxin perceived for root growth inhibition? What physiological modules does it regulate? Which proteins are responsible for the action of auxin in the root?
Cellular growth is the result of the balance between the cellular pressure and the properties of the cell wall. Cell wall pH is crucial in influencing the cell wall properties. How do cells regulate and perceive the pH of their cell walls? How do cells perceive and regulate their turgor pressure?
To study growth, we use advanced live-cell imaging of elongating roots of Arabidopsis thaliana. We are building an imaging set-up to perform automated root tip observation and tracking. We focus on visualization of physiological processes using genetically encoded fluorescent protein sensors and use of advanced image analysis to quantify the dynamics of these processes. We are establishing a microfluidic platform to be able to treat, manipulate and observe growing roots in real time.
We employ molecular biology approaches to identify proteins involved in cell growth regulation. We focus on visualization of the protein expression, localization and dynamics using fluorescent protein reporters and confocal microscopy.