Research -what’s ongoing?
The Persson lab investigates how plants are making cell walls, with a focus on cellulose synthesis, and how the cell wall can communicate with the interior of the cell to make more or less of certain cell wall polymers. We are using a range of molecular, cell biology and genetic techniques mainly in the plant model species Arabidopsis, but we are also working on related questions in rice, Marchantia and other crop plants.
Microtubules and cellulose synthesis
The synthesis of cellulose is typically guided by cortical microtubules in expanding plant cells. We have identified several proteins that are important for the maintenance of the connection between the cellulose synthase (CESA) complex and the microtubules, including the Cellulose Synthase Interacting (CSI)1/POM2 (Gu et al., PNAS, 2010; Bringmann et al., Plant Cell, 2012) and the Companion of Cellulose Synthase (CC) 1 and 2 (Endler et al., Cell, 2015; Kesten et al., Nature Comm, 2019). The CC proteins are particularly interesting as they are needed to re-assemble microtubules after environmental stress, such as salt, which in turn maintains the capacity of the plant cell to make cellulose and thus to grow. We have recently identified another protein family, which are important to maintain the lateral stability of cortical microtubules and to direct the CESA complexes along them (Liu et al. Dev Cell,2016). We aim to better understand what the function of these and other proteins are in cellulose synthesis in context of microtubule dynamics. These aims are addressed through in vivo and in vitro imaging and basic genetics and molecular techniques.
Microtubules (red) and Cellulose Synthase (green) tagged with fluorescent proteins in leaf cell in Arabidopsis. Courtesy of Dr Zengyu Liu.
Cell wall sensing
The status of the cell wall needs to be sensed by the cell to maintain structure and function of it during growth and changes in the environment. It is anticipated that an elaborate framework would be needed to maintain such a signaling. For instance, almost a thousand Receptor-like kinases are encoded by a typical plant genome, and many of these are expected to be present at the plasma membrane where they could have a cell wall sensing function. However, only a handful of these kinases have been characterized and so not much is known about cell wall sensing in plants. We are interested in finding out ways that the plant cell is doing this, and we have identified several potential receptor-related protein that appear to be involved in this process. One of these regulate the growth of root hairs where it controls cell wall synthesis and maintain calcium and pH signals to sustain polar growth. Another cell wall-related signalling unit contains a G-protein coupled-like receptor module that specifically regulates the secretion of the CESAs to the cell surface. We are currently attempting to find out how these, and other, proteins sense wall changes and what the cellular functions the proteins then regulate.
Organization of the cytoskeleton
The cytoskeletal components, (filamentous actin and microtubules) greatly contribute to cell wall synthesis and to plant cell and tissue morphology. We are interested in assessing the re-organization of the cytoskeleton and in finding new components that influence the behavior of the cytoskeleton. We have developed plug-ins and tools with which we can automatically trace cytoskeletal components and analyze their behavior (Breuer et al., PNAS, 2018; Yu et al., Nature Plants, 2019), and we have also found that the cytoskeletal components transiently interact (Sampathkumar et al. Plant Cell, 2011). We use both fluorescently-tagged cytoskeletal markers in Arabidopsis plants, as well as in vitro based analyses using TIRF microscopy to address questions relating to how certain proteins influence the cytoskeleton. In addition, we make image analyses plug-ins to both qualitatively and quantitatively understand how these proteins affect organization and behavior of the cytoskeleton.
Extraction and quantification of actin cytoskeleton from Arabidopsis hypocotyl cell expressing GFP-FABD.
Making the leap from Arabidopsis to other plants
Arabidopsis is a great model organism for genetics and cell biology, and we have successfully used this species to better understand how cell walls are built and maintained. However, efforts are certainly needed to move beyond Arabidopsis. To do this we are now also working in rice and canola, in which we are trying to understand the function of many of the proteins we have discovered in Arabidopsis. We here aim to establish rice as a nice model for cell biology studies and to also find processes and protein functions that differ from those in Arabidopsis. These efforts include understanding how microtubules guide the CESAs and how the primary and secondary walls are regulated. In addition, we have recently started to use Marchantia as a useful tool to explore cell wall synthesis due to reduced genetic redundancy.
Our work has had major impacts on the cell wall research community, resulting in that the work from our group was highlighted as a highly cited by Thomson Reuter in 2016, 2017 and 2018.