My research is focused on mechanisms regulating plant growth and development, especially root development, and the roles played by plant growth regulating substances (plant hormones) in the developmental processes that lead to the formation of the root system.

KarinLjung T1A8799 ElisabethOhlsonWallin 1920x1080Photo: Elisabeth Ohlson Wallin
Over the years, my research has continuously been focused on mechanisms that regulate plant growth and development. In particular, I am interested in two key mechanisms: i) The roles played by plant hormones in primary and secondary root development; and ii) The role of plant hormones in the integrative coordination of above and below ground growth. In order to answer fundamental questions, e.g. how lateral roots are initiated, my group is employing Arabidopsis thaliana as a model organism, but we have recently started to translate this research also into trees and crops.

Auxins and cytokinins are plant hormones that are essential throughout the whole life cycle of higher plants. They play pivotal roles in key growth and developmental processes, and they are central to coordinate responses to different environmental variables. Both hormones act in a concentration-dependent manner, and a complex range of regulatory mechanisms act in concert to ensure that the levels of these compounds are optimal for growth and development. We are studying auxin and cytokinin metabolism, transport and signalling, how these processes are regulated by internal and external signals, and how they influence primary and secondary root development. Recently, my team discovered an enzyme responsible for auxin degradation, DIOXYGENASE FOR AUXIN OXIDATION 1 (DAO1), which opens up the possibility to regulate auxin homeostasis in plants via the auxin degradation pathways. Potentially, this can lead to new ways of modifying the root system architecture.

We have recently developed methods for plant hormone profiling in very small amounts of plant tissues, using liquid chromatography coupled to tandem mass spectrometry analysis (LC-MS/MS). We have also developed techniques for using Fluorescent Activated Cell Sorting (FACS) in combination with mass spectrometry analysis to analyse auxin and cytokinin distribution and metabolism within the Arabidopsis root at cellular and sub-cellular resolution. The formation of local hormone gradients and maxima/minima in developing plant tissues has been shown to be very important for organogenesis, through the coordinated regulation of cell division, cell differentiation and cell elongation.

Bild hemsidan2019 Ruben 1920width Arabidopsis mutant isolated in a genetic screen, showing (A) hyponastic leaves and (B) an increase in lateral root formation. (C) Confocal image of a lateral root tip from the DR5::VENUS transgenic line, used as parental line in our genetic screen. (Photos: Rubén Casanova-Sáez)
KarinLjung spruce(A) 2 week-old Norway spruce seedling. (B) Three-dimensional picture of the root system from a spruce plant growing in soil. (C) Confocal laser scanning microscope image of a section from the primary root of a 2 week-old Norway spruce seedlin (Photos: Federica Brunoni).
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