Monday Seminar Series: 'Deciphering halotropism; Combining models and experiments to understand how plant roots grow away from salt'

Individual plant organs display so called tropisms, directional growth towards
or away from stimuli. Well known examples are growth of shoots away from and
roots towards gravity. Most plant tropisms arise from an asymmetry in the organ's auxin pattern that subsequently generates an asymmetry in growth rates resulting in bending of the plant organ. Recently a new tropism was discovered,
halotropism, the bending of plant roots away from regions with high salt
concentration. In this talk I will demonstrate how detailed modeling of auxin
patterning dynamics in plant roots combined with experiments allowed us to
elucidate the mechanistic underpinnings of this tropism.

Notably, while the original study showed an asymmetry in a single particular
auxin transporter that was deemed sufficient to drive halotropism, we
demonstrated that this asymmetry can in fact generate only minute asymmetries
in auxin insufficient to induce any bending. Using our model we predicted
additional auxin transporters, as well as feedbacks between auxin and the
levels of active transporters to be essential to generate sufficiently large
asymmetries at sufficient speed. These predictions were subsequently confirmed
experimentally. In my talk I will discuss how the interactions between
different auxin transporters and feedback between auxin and its transporters
allow amplification and speedup of auxin asymmetries.