Integrated analysis of stem cell function in plant growth and development

Lead Research Organisation: CARDIFF UNIVERSITY
Department Name: School of Biosciences


Stem cells are of central importance in the development of both plants and animals, since they are a self-maintaining reservoir of unspecialised cells that provide the precursor cells for tissue and organ formation. Stem cells have the ability to maintain temselves and also to produce daughter cells with different characteristics (called 'differentiated' cells). The maintenance of stem cells is therefore crucial for all multicellular organisms and is of outstanding significance for regenerative biology in medicine and agriculture. Given the life-long importance of stem cells, they are tucked safely from harm's way, in so-called stem cell niches that provide a microenvironment promoting self-renewal and inhibiting cell differentiation into different cell types. Plant stem cell niches are located in meristems at root and shoot tips, and are pivotal to the production of new organs and tissues throughout the plant life cycle that in some species can span several thousand years. In woody plants a further specialised cylindrical meristem within the stem, the cambium, is of particular importance in secondary thickening that results in production of woody material, and this also contains stem cells. In this proposal, we seek to use microarray analysis to identify the genes that control behaviour of these different populations of stem cells. Microarrays allow simultaneous measurement of the expression of all genes in a sample. We will combine this with advanced cell sorting technologies and techniques to increase the number of stem cells by transgenic regulation, and this will allow us to identify common and distinct mechanisms that control the proliferation of different stem cells and whether and when they differentiate to give rise to different cell types in their respective tissues. In plants, these signals that specify and maintain stem cells and the genes involved are poorly understood. We also seek to understand how stem cells respond to cues from the environment. We propose a European network composed of the world leading groups involved in understanding (1) root stem cells [Ben Scheres, Utrecht, Netherlands], (2) shoot stem cells (Thomas Laux, Freiburg, Germany], (3) the cambial stem cells (Yka Helariutta, Helsinki, Finland), together with the group of Jim Murray (Cambridge, UK) who are experts in the control of cell division, and Aurelio Camphilo (Porto, Portugal), experts in image analysis of growing plant tissue.

Technical Summary

Stem cells are essential to the growth and development of plants and provide the ultimate origin of all agriculture and forestry. Although some key genes required for the establishment and maintenance of stem cells are identified, we lack information on the networks governing cell differentiation and cell cycle of different stem cell populations, on how these mechanisms determine common and specific behaviors of the different stem cell groups and how they integrate stem cell activity with changing environmental conditions. This proposal integrates the work of world-leading labs that perform key research on stem cell populations of the shoot, root and vascular meristems, cell cycle control, growth modeling and image analysis. Europe has a global lead in plant stem cell research and cell division control, and this proposal will integrate the research of the different labs involved, creating new synergies and substantial added value. New tools and strategies combining genomics, reverse genetics, smart genetic screens, and novel cell biology will be exploited to address the key issue of how specification of stem cell regions by transcription factors translates to cellular mechanisms for division and differentiation and identify common and distinct regulatory networks in different stem cell populations. [from ERA-PG project]


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Description New links between stem cells and regulators of cell division in the plant root that control growth.The integration of cell division in root growth and development requires mediation of developmental and physiological signals through regulation of cyclin-dependent kinase activity. Cells within the pericycle form de novo lateral root meristems, and D-type cyclins (CYCD), as regulators of the G1-to-S phase cell cycle transition, are anticipated to play a role. Here, we show that the D-type cyclin protein CYCD2;1 is nuclear in Arabidopsis thaliana root cells, with the highest concentration in apical and lateral meristems. Loss of CYCD2;1 has a marginal effect on unstimulated lateral root density, but CYCD2;1 is rate-limiting for the response to low levels of exogenous auxin. However, while CYCD2;1 expression requires sucrose, it does not respond to auxin. The protein Inhibitor-Interactor of CDK/Kip Related Protein2 (ICK2/KRP2), which interacts with CYCD2;1, inhibits lateral root formation, and ick2/krp2 mutants show increased lateral root density. ICK2/KRP2 can modulate the nuclear levels of CYCD2;1, and since auxin reduces ICK2/KRP2 protein levels, it affects both activity and cellular distribution of CYCD2;1. Hence, as ICK2/KRP2 levels decrease, the increase in lateral root density depends on CYCD2;1, irrespective of ICK2/CYCD2;1 nuclear localization. We propose that ICK2/KRP2 restrains root ramification by maintaining CYCD2;1 inactive and that this modulates pericycle responses to auxin fluctuations.
Exploitation Route Primarily of academic interest.
Sectors Agriculture, Food and Drink

Description Size Matters: A systems approach to understanding cell size control in a developing multicellular tissue
Amount £421,568 (GBP)
Funding ID BB/S003584/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 02/2019 
End 01/2023