Dr Stefan Kepinksi, Leeds
Gravity and the shaping of plant form: growth angle control in lateral root and shoot branches
The overall shape of plants, the space they occupy above and below ground, is determined largely by the number, length, and angle of their lateral branches. For the most part root and shoot branches grow at angles that are non-vertical, a crucial adaptation allowing plants to optimise the capture of resources above and below ground. Importantly, many of these branches are maintained at specific angles with respect to gravity, rather than to the main or parent axis per se. These growth angles, known as gravitropic setpoint angles or GSAs, are intriguing because their maintenance requires that lateral root and shoot branches are able to effect tropic growth both with and against gravity. We have shown that this capacity to maintain non-vertical GSAs requires the action of an auxin transport-dependent antigravitropic offset mechanism that counteracts graviresponse in lateral roots and shoots. We are now using genetic, cell biological, and computational approaches to understand both the molecular basis of this offset mechanism and how the interaction of gravitropism and antigravitropism can give rise to the wonderful variation in patterns of growth angle control observed throughout nature.