Auxins and strigolactones in shoot branching

Branching of plants is an important for yield. For instance, shoot branching in rice results in multiple tillers, and therefore more rice grains per plant while root branching increases the potential to assimilate nutrients from the soil. Branching of shoot and root is under control of hormonal signals, which in turn are affected by light and local soil conditions: in shade the plant limits its branching to divert all energy into elongation growth and under low soil phosphate the plant limits branching to save phosphate utilisation.

How is branching of shoot and root controlled by hormonal signals?

In this project we study the effect of auxins and the recently discovered phytohormone strigolactones on branching in shoots and roots. We make use of mutants in branching, plant manipulation (e.g. decapitation) to affect shoot branching, hormonal measurements and treatments and reporter plants which enable visualisation of the endogenous hormone signalling in the living plants.

We use plants that emit light related to local auxin signalling activity (using DR5-luciferase reportergene). These light activity measurements show that auxin signalling in plants is very dynamic. Currently we are characterising auxin transport through the stem of a plant. These measurements can be combined with sampling at specific time points to relate local auxin signalling to local free and local conjugated auxin levels.

The results from the hormone and luciferase reporter plant measurements are combined in a comprehensive model of hormonal interactions in which we try to understand the key steps that control outgrowth of a side root or outgrowth of an axilary bud.

Techniques: construction novel reporter genes, in planta LUC image analysis. Validating computer model hormone/light interactions (with CSA) plant growth, making crosses, genomic analysis progeny plants, hormone extractions and measurements with LCMS triple Quad.

Related PhD projects:

Physiological control of plant growth under negative DIF treatment (TTI-GG, PhD Ralph Bours)