Heidstra Group - Stem cell specification and regeneration

A central question in biology is what determines the fate of a cell, tissue or even organ. Fate decisions taking place during embryogenesis are reiterated during the life of the plant to generate the adult architecture. Starting point in our studies on fate specification is the model plant Arabidopsis thaliana and its anatomically simple root system.

Mixed fate’ divisions, giving rise to daughter cells with characteristics of two tissue layers, are mutations that are common in plants but near-absent in other organisms. We investigate how the SCHIZORIZA protein can influence several such divisions during root development, which points to an atypical mechanism for plant asymmetric cell division. As SCZ encodes a heat-shock transcription factor, another goal is to investigate its role in stress response. Questions? Ask Honglei Wang.  

Stem cell fate involves the redundant PLETHORA (PLT) AP2-domain transcription factors that play a major role in stem cell niche specification and controlling differentiation rate in the meristem. We explore how the many target genes of these transcription factors orchestrate division and differentiation during the progression from stem cell to differentiated cell, while keeping an eye out for other functions in plant development.  

Embryonic fate instruction. Zygotic embryogenesis in many plants, including Arabidopsis thaliana, usually kicks off with the asymmetric division of the zygote, forming a smaller apical cell that generates the embryo proper and large basal cell initiating the suspensor. Natural zygotic poly-embryony originating from this normally quiescent suspensor is observed in several species but can also be experimentally induced, demonstrating the potential of the suspensor to change fate and undergo embryonic development. By studying poly-embryonic mutants we aim to unravel the molecular mechanisms controlling fate instruction during embryogenesis. (Honglei Wang)

Fate decisions are instrumental during plant regeneration, but regenerative capacity varies widely among species and tissue types. This regenerative recalcitrance can be particularly distressing for the application of modern plant propagation and breeding techniques if it concerns important crop cultivars. Experiments in Arabidopsis demonstrate that during these steps, cells are first persuaded to change fate towards root stem cell-like identity and subsequently are reprogrammed to acquire shoot fate. We apply our knowledge on root stem cell niche biology to study stemness and regeneration. (Jana Wittmer, Tristan Wijsman) 

Root system architecture (RSA) includes two aspects of the root system: its shape and its structure. We study the genes that control RSA in lettuce for optimal growth, either on soil or on hydroponics. To identify key RSA genes, we explore natural variation in a large collection of Lactuca species. The identified genes as well as known root architecture genes are functionally characterized in lettuce by genetic modification. (Anneke Horstman, Francesca Bellinazzo)  

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