inducible-cell-type-specific-expression-arabidopsis-thaliana-through

Inducible, Cell Type-Specific Expression in <em>Arabidopsis thaliana</em> Through LhGR-Mediated <em>Trans</em>-Activation

Inducible, tissue-specific expression is an important and powerful tool to study the spatio-temporal dynamics of genetic perturbation. Combining the ...

Centre for Organismal Studies (COS) Heidelberg

Understanding the context-specific role of gene function is a key objective of modern biology. To this end, we generated a resource for inducible cell type-specific transactivation in Arabidopsis () based on the well-established combination of the chimeric GR-LhG4 transcription factor and the synthetic  promoter. Harnessing the flexibility of the GreenGate cloning system, we produced a comprehensive set of transgenic lines termed GR-LhG4 driver lines targeting most tissues in the Arabidopsis shoot and root with a strong focus on the indeterminate meristems. When we combined these transgenic lines with effectors under the control of the  promoter, we observed tight temporal and spatial control of gene expression. In particular, inducible expression in F1 plants obtained from crosses of driver and effector lines allows for rapid assessment of the cell type-specific impact of an effector with high temporal resolution. Thus, our comprehensive and flexible method is suitable for overcoming the limitations of ubiquitous genetic approaches, the outputs of which often are difficult to interpret due to the widespread existence of compensatory mechanisms and the integration of diverging effects in different cell types.

A Comprehensive Toolkit for Inducible, Cell Type-Specific Gene Expression in Arabidopsis.

A reduced rate of stem cell division is considered a widespread feature which ensures the integrity of genetic information during somatic development of plants and animals. Radial growth of plant shoots and roots is a stem cell-driven process that is fundamental for the mechanical and physiological support of enlarging plant bodies. In most dicotyledonous species, the underlying stem cell niche, the cambium, generates xylem inwards and phloem outwards. Despite the importance and intriguing dynamics of the cambium, the functional characterization of its stem cells is hampered by the lack of experimental tools for accessing distinct cambium sub-domains. Here, we use the hypocotyl of  to map stem cell activity in the proliferating cambium. Through pulse labeling and genetically encoded lineage tracing, we find that a single bifacial stem cell generates both xylem and phloem cell lineages. This cell is characterized by a specific combination of  (),  and  gene activity and a high division rate in comparison with tissue-specific progenitors. Our analysis provides a cellular fate map of radial plant growth, and suggests that stem cell quiescence is not a general prerequisite for life-long tissue production.This article has an associated 'The people behind the papers' interview.

Bifacial cambium stem cells generate xylem and phloem during radial plant growth.

Developmental plasticity, defined as the capacity to respond to changing environmental conditions, is an inherent feature of plant growth. Recent studies have brought the phloem tissue, the quintessential conduit for energy metabolites and inter-organ communication, into focus as an instructive developmental system. Those studies have clarified long-standing questions about essential aspects of phloem development and function, such as the pressure flow hypothesis, mechanisms of phloem unloading, and source-sink relationships. Interestingly, plants with impaired phloem development show characteristic changes in body architecture, thereby highlighting the capacity of the phloem to integrate environmental cues and to fine-tune plant development. Therefore, understanding the plasticity of phloem development provides scenarios of how environmental stimuli are translated into differential plant growth. In this Review, we summarize novel insights into how phloem identity is established and how phloem cells fulfil their core function as transport units. Moreover, we discuss possible interfaces between phloem physiology and development as sites for mediating the plastic growth mode of plants.

Thomas Greb

Department of Developmental Physiology

Centre for Organismal Studies (COS) Heidelberg

Inducible, Cell Type-Specific Expression in Arabidopsis thaliana Through LhGR-Mediated Trans-Activation