Cytokinin and its impact on radial expansion of root systems

As soon as a seed germinates, plant growth relates to gravity to ensure that the root penetrates the soil and the shoot expands aerially. Mechanisms of positive and negative orthogravitropism of primary roots and shoots are relatively well understood. In contrast, lateral organs show more complex growth behavior, which largely remains enigmatic. Root growth towards gravity is an important trait that ensures sessile plants to anchor and to cover its surroundings. Lateral roots (LRs) are important to increase the root soil surface and allow for radial expansion of the root system (plagiotropism). For such a radial exploration of the substrate, LRs seemingly suppress positive gravitropic growth and show a defined gravitropic set-point angle (GSA). Despite its eminent importance for habitat compatibility, productivity, and drought stress tolerance, it so far remains largely unknown how plants control radial or axial root system expansion and, hence, substrate coverage. We have illustrated that plants from diverse geographical origin have differences in GSA-derived root system architecture. We determined GSA of emerged lateral roots in naturally occurring Arabidopsis accession lines and have used genome-wide association (GWA) techniques to reveal novel molecular components involved in GSA determination. With the help of this grant we will characterize such an internal signal regulating root system plasticity, using developmental genetics, physiological and cell biological procedures. This work will provide substantial mechanistic insight into phyto-hormonal crosstalk, shaping plant architecture.

We have illustrated that Arabidopsis plants from diverse geographical origin have differences in Gravitropic Set-point Angle (GSA)-derived root system architecture. We determined GSA of emerged lateral roots in naturally occurring Arabidopsis accession lines and have used genome-wide association (GWA) techniques to reveal novel molecular components involved in GSA determination. With the help of this grant we have in depth characterized such an internal signal regulating root system plasticity, using developmental genetics, physiological and cell biological procedures.