The regulation of vascular pattern in flowering plants

The xylem and phloem provide the long distance transport mechanisms for water, sugars and minerals between the root and the shoot as well as providing the plant with rigid stems and roots. Manipulation of these tissues may offer important benefits in biofuel production, increased stem rigidity to prevent lodging in cereal crops and controlling water uptake. I am also interested in pattern formation, and the root vascular cylinder provides an excellent system for addressing how positional information is gained as bisymmetry is established from a radially symmetric pattern.

The mutually inhibitory interaction between the hormones auxin and cytokinin defines distinct domains of hormonal signalling and these specify vascular pattern. Interaction between the auxin and cytokinin signalling and transport pathways occur at several nodes. High auxin output directly promotes the expression of the cytokinin signalling inhibitor, AHP6. High cytokinin signalling regulates the expression and subcellular localization of the auxin efflux carriers PIN1, PIN3 and PIN7 by an unknown mechanism. In Arabidopsis roots this mutually inhibitory interaction generates an auxin response maxima in a central axis, in which xylem differentiates in a diarch pattern. This is flanked on both sides by two domains of high cytokinin signalling output in which procambial and phloem cells differentiate.

This research will take a systems biology approach combining experimental biology with multiscale computational modelling at CPIB to uncover how the same basic components can be used to generate alternative vascular patterns in diverse species. In this project we are identifying differences in subtle aspects of the vascular patterning mechanisms that can generate the variety of vascular patterns observed throughout vascular plants. This will improve our understanding of how standard “genetic toolkits” can be applied to creating the huge diversity of patterns that we see in the natural world.