Universiteit Leiden

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Plant BioDynamics Laboratory


PBDL favors multidisciplinary research. Depending on the problems under investigation, PBDL establishes collaborations between experts from for example molecular genetics, molecular and electro cell physiology, biochemistry, organic chemistry, analytical mathematics, mathematical statistics and computational sciences.

Currently, the research at the Plant BioDynamics Laboratory is organised into three lines:

1. Mathematical and computational analysis of the dynamics of polar transport of the plant hormone auxin


The plant hormone auxin (IAA) belongs to a complex system of chemical messengers which have a pivotal role in the coordination of growth and development between different parts of the plants, such as for example the shoot and root system.

We investigate the dynamics of long-distance polar auxin transport (PAT) by mathematical and computational analysis of experimental transport data. In particular, we investigate the functional role of the so-called PIN proteins which are assumed to be the polar distributed intracellular auxin-anion export carriers as postulated in the chemiosmotic theory of PAT. Our results already suggest that in spite of all the indirect evidence PINs are not solely or not at all responsible for PAT.

2. The Green algae Chara as model system for intra and inter cellular transport processes


The fresh-water green algae Chara is closely related to terrestrial plants (they both belong to the clade Streptophyta). Moreover, the morphology of Chara is plant-like, but is relatively simple: it consist of a rhizoid (root-like), relatively long (up to 10 cm) internode cells interconnected by short node cells that are surrounded by peripheral cells from which the characteristic whorls of branches arise. In particular this relatively simple morphology, renders Chara an attractive model system for the study of transport processes (e.g. auxin transport) at the cellular, subcellular and molecular level.

Although it is known that Chara produces the natural auxin IAA, its transport and mechanism of action in Chara were unknown. However, over the past few years we were successful to be the first in demonstrating the presence of directional transport of IAA comparable to polar auxin transport (PAT) in terrestrial plants. Our program is now aimed at understanding the mechanism of this transport.

An important mode of action of auxin in terrestrial plants is regulation of the action of plasma membrane proton pumps (PM-H+-ATPases). As part of a PhD program, we made a start in characterizing PM-H+-ATPases in Chara with a view to elucidate their regulation. This was done by combining electrophysiology and molecular genetic approach. The tentative conclusion is that Chara cells have PM-H+-ATPases, which are structurally slightly different from those from terrestrial plants suggesting that they may be regulated by a different mechanism whereby auxin may play a less direct role.

A follow-up of this study, which may shed light on the evolution of PM H+-ATPases from green algae to higher plants, is in progress.

3. Optimality in plant properties and processing


Argumentation using the concept of optimality can and have been used in biology to predict and understand various properties of living organisms. The main line of reasoning is, that evolution has shaped the organism such that it can function optimally in its habitat and also adapt optimally to changes therein. By means of mathematical modeling, these optimality concepts can be translated into the question of finding the optima of (possibly) objective functions under constraints defined by the model. This can be approached using computational techniques for global (multi-objective) optimization.

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