Biomedical subjects

Anne-Gaëlle Rolland-Lagan

Publications and source records attributed to Anne-Gaëlle Rolland-Lagan.

5 recordsLinked to original sources

PubMed2005

Modeling plant morphogenesis.

Applications of computational techniques to developmental plant biology include the processing of experimental data and the construction of simulation models. Substantial progress has been made in these areas over the past few years. Complex image-processing techniques are used to integrate sequences of two-dimensional images into three-dimensional descriptions of development over time and to extract useful quantitative traits. Large amounts of data are integrated into empirical models of developing plant organs and entire plants. Mechanistic models link molecular-level phenomena with the resulting phenotypes. Several models shed light on the possible properties of active auxin transport and its role in plant morphogenesis.

Computer Simulation↗

PubMed2005

A computational method for inferring growth parameters and shape changes during development based on clonal analysis.

We describe a method for estimating growth parameters in various regions of a developing organ undergoing cell divisions, along with the corresponding changes in organ shape. Growth parameters are computed by coupling clonal analysis with a growth model, allowing a wide range of developmental stages to be covered. The method was applied to the development of dorsal petal lobes of Antirrhinum majus. The resulting description of growth patterns and shape changes is consistent with direct observations using scanning electron microscopy. This method can potentially be applied to other organs, and opens the way to comparative studies of growth and gene expression patterns.

Antirrhinum↗

PubMed2005

Reviewing models of auxin canalization in the context of leaf vein pattern formation in Arabidopsis.

In both plants and animals vein networks play an essential role in transporting nutrients. In plants veins may also provide mechanical support. The mechanism by which vein patterns are formed in a developing leaf remains largely unresolved. According to the canalization hypothesis, a signal inducing vein differentiation is transported in a polar manner and is channeled into narrow strands. Since inhibition of auxin transport affects venation patterns, auxin is likely to be part of the signal involved. However, it is not clear whether the canalization hypothesis, initially formulated over 25 years ago, is compatible with recent experimental data. In this paper we focus on three aspects of this question, and show that: (i) canalization models can account for an acropetal development of the midvein if vein formation is sink-driven; (ii) canalization models are in agreement with venation patterns resulting from inhibited auxin transport and (iii) loops and discontinuous venation patterns can be obtained assuming proper spacing of discrete auxin sources.

Arabidopsis↗

PubMed2004

The genetics of geometry.

Although much progress has been made in understanding how gene expression patterns are established during development, much less is known about how these patterns are related to the growth of biological shapes. Here we describe conceptual and experimental approaches to bridging this gap, with particular reference to plant development where lack of cell movement simplifies matters. Growth and shape change in plants can be fully described with four types of regional parameter: growth rate, anisotropy, direction, and rotation. A key requirement is to understand how these parameters both influence and respond to the action of genes. This can be addressed by using mechanistic models that capture interactions among three components: regional identities, regionalizing morphogens, and polarizing morphogens. By incorporating these interactions within a growing framework, it is possible to generate shape changes and associated gene expression patterns according to particular hypotheses. The results can be compared with experimental observations of growth of normal and mutant forms, allowing further hypotheses and experiments to be formulated. We illustrate these principles with a study of snapdragon petal growth.

Gene Expression Regulation, Developmental↗

PubMed2003

Growth dynamics underlying petal shape and asymmetry.

Development commonly involves the generation of complex shapes from simpler ones. One way of following this process is to use landmarks to track the fate of particular points in a developing organ, but this is limited by the time over which it can be monitored. Here we use an alternative method, clonal analysis, whereby dividing cells are genetically marked and their descendants identified visually, to observe the development of Antirrhinum (snapdragon) petals. Clonal analysis has previously been used to estimate growth parameters of leaves and Drosophila wings but these results were not integrated within a dynamic growth model. Here we develop such a model and use it to show that a key aspect of shape--petal asymmetry--in the petal lobe of Antirrhinum depends on the direction of growth rather than regional differences in growth rate. The direction of growth is maintained parallel to the proximodistal axis of the flower, irrespective of changes in shape, implying that long-range signals orient growth along the petal as a whole. Such signals may provide a general mechanism for orienting growth in other growing structures.

Antirrhinum↗