Karlsruhe Institute of Technology - Peter Nick - What are the goals of our research?

The Japanese Asa-gao ("Morning Glory") represents an extreme example for developmental regulation through the environment. Usually, the Morning Glory flowers in autumn, when the days become shorter. However, when the seedlings experience a single long night (16 hours darkness), they will start to flower as if the autumn had come, although they just have formed two cotyledons (image Prof. Masaki Furuya, Tokyo). To measure day length, the plant uses the plant pigment phytochrome.

Life is not easy. There are two ways to respond to this: run away or adapt. Animals run away, plants adapt. They do not only adapt their metabolism to the challenges posed by the environment, they also change shape and development to secure their survival. Many plants "measure", for instance, the length of the day and decide then, whether they should flower or not. By this they ensure that seeds are produced in time before the onset of winter and safeguard the survival of their descendants. As a consequence of this survival strategy, plants have evolved an almost incredible ability for regeneration. In principle, each individual plant cell can generate the whole organism, something which only egg cells can do in animals - thus, a plant basically consists of stem cells. All cells are by their nature equivalent, there is no hierarchy. How can from such equivalent elements that are, in addition, quite autonomous, emerge an ordered whole without the control of a steering "Big Boss"?

This is the issue, we want to understand and therefore, our work is motivated by two questions:

1. How do plants perceive their environment and how can they decide, which developmental path to choose?

2. How does this decision culminate in altered shape and how is growth controlled in space?

From these two questions our central topics have developed:

Cytoskeleton: It consists mainly from the two proteins tubulin and actin. These building blocks are organized into filamentous polymers, the microtubules and the actin filaments. These filaments control growth and division of the cell, but also act as guiding tracks for intracellular movements. The organization of microtubules and actin filaments is controlled depending of external stimuli such as light, gravity or touch, but also depending on development and phytohormones, and this cytoskeletal organization defines cell shape. We recently discovered that, in addition, the plant cytoskeleton acts as a kind of sensory organ for the cell.

Pattern Formation: The establishment of multicellularity represented a big step in evolution, because multicellularity allows for division of labour. Different cells can specialize for different functions and this is advantageous for the whole community of cells. But division of labour requires that somebody assigns different jobs. This might be done by a central steering structure that is hierarchically controlling the other cells. However, plants are innate democrats. All cells are equivalent. The exciting question of pattern formation in plants is that equivalent elements, that, in addition, are basically autonomous, form an ordered whole and this, whithout a "Big Boss". This requires that cells communicate and assign functions to individual cells. Their "language" is based on the plant hormone auxin. We have discovered that this phenomen can be studied in cell cultures from tobacco. Those cells produce a file by directional cell divisions, and this file behaves as a kind of "minimal organism". The tip cells produce auxin waves that synchronize the divisions in the cell file - using this model we can now study, how plant cells communicate and decide upon developmental fates.

Nano-Cell Biology: The nanosciences have generated new tools that are also useful for our questions. In close cooperation with chemists, physicists, and engineers we develop these tools such that they are amenable to plant cell biology. Our goal is, not only to watch, how molecules and cellular events respond to signals - no, we want also to manipulate the dance of molecules and thus control cellular behaviour.

Cell Biology and Evolution: In the course of evolution multiple life forms arose that have adapted to quite different envirnonmental conditions and different strategies of survival. Since all living beings are built from cells, evolution is expected to leave traces in the biology of individual cells. However, evolutionary cell biology is still in its beginnings. Comparative cell biology of plants should advance our understanding of evolution. Conversely, the biology of plant cells is fundamentally different from that of animal cells. This can be only understood by understanding the history. In other words: there is no understanding of plant cell biology without understanding its evolution.