Phytohormonal control of cellular growth: Auxin-dependent growth regulation on subcellular, cellular, tissue and organ level.
Leader: Assoc.Prof. Dr. Jürgen Kleine-Vehn
Multicellular organisms have independently arisen a number of times, leading to diverged life forms such as animals and plants. Plants have elaborated on a sessile lifestyle with remarkable plasticity for shaping their body plan according to the ever-changing environment. Most intriguingly, plants are characterized by unequalled postembryonic growth and regeneration potential that is tightly controlled by phytohormones. Even though plants have outstanding importance for our cultural life and more important for the ecosystem earth, little is known about cellular mechanism that allows this unique growth regulation. The phytohormone auxin (auxein: to grow) is tightly linked with plant growth regulation. However, our global understanding of how small molecules, such as auxins, can carry the required information for shape regulation in plants, is largely ill defined.
To obtain truly mechanistic insights into differential growth regulation in plants, we are addressing upstream and downstream components that execute or instruct auxin-dependent, differential growth regulation on subcellular, cellular, tissue, and organ level. We focus on three main research questions:
1.) How does a plant coordinate differential growth on an organ level to establish its architecture?
To investigate differential organ growth, we focus on asymmetric growth regulation in lateral roots in response to gravity. Auxin controls the angular growth of lateral roots and thereby determines whether a root system deeply penetrates the soil or expands radially (Ruiz Rosquete et al., 2013). We currently investigate how intrinsic and extrinsic cues shape this root architecture trait.
2.) How is cell size determined in neighbouring tissues?
We investigate neighbouring root epidermal cell files (tricho- and atrichoblasts) that display distinct cell size control. We utilize these cell files, functionally facilitating the root-soil interface, as a novel model to monitor how hormonal signals get integrated to execute cell size determination (Löfke et al., 2013). We currently unravel cellular requirements for auxin-dependent cell size determination.
3.) How is auxin controlled within a cell?
We address subcellular mechanisms that affect cellular auxin homeostasis. To address auxin homeostasis on a sub- and cellular resolution, we are unravelling the importance of the PILS putative auxin facilitator family at the endoplasmic reticulum (Barbez et al., 2012; Feraru et al., 2013; Barbez and Kleine-Vehn, 2013). This work will broaden our understanding of how single cells in a tissue context regulate its sensitivity to auxin.
We investigate auxin-dependent growth regulation at different levels to obtain a comprehensive understanding of plant growth regulation. Notably, our research efforts are directly linked to agriculturally important developmental aspects (e.g. epidermal surface enlargement, tropistic growth, or water and nutrient uptake) and, hence, our research will provide not only important insights into general mechanisms of how plants regulate, monitor, and trigger growth, but will have importance for applied research fields.