Functional analysis of a putative master regulator of plant development

Unlike animals, plants are sessile organisms. As such, they are exposed to wide environmental variations to which they need to adapt, or that they need to avoid in order to survive and maintain growth.  To achieve this, they have evolved sophisticated mechanisms for sensing environmental fluctuations and adjusting their development and needs accordingly.  Despite presenting fundamental divergences in their ontogeny and specificity in regulatory growth factors, plants and animals share some core molecular components for tuning growth and development to prevailing conditions.  One is the Translationally-Controlled Tumor Protein, TCTP, present in all eukaryotes.  In animals, TCTP is crucial for several core cellular processes including apoptosis, cellular proliferation and growth, and tissue patterning, and the regulation of major pathologies, foremost cancer, diabetes and immunity.  Plant TCTPs are much less known but are also vital.  Loss of TCTP function is embryo lethal, leads to slower growth and dwarfism, impairs root development and hormonal homeostasis.

In my PhD project, I investigated the function of the major Arabidopsis TCTP isoform in root development, at the whole organ, cellular and molecular levels; and I probed the possibility it may have an inter-organ signalling role.

During my seminar, I will present my findings on the role of TCTP as a promoter of cell proliferation and expansive cellular growth, and a regulator of their coordination in the regulation of root elongation.  I will then present experiments which uncovered one TCTP direct molecular downstream target in these functions and also embryogenesis.

Contrary to animal TCTPs, plant TCTPs are not known to assume extracellular, signalling functions.  I will show that long-distance, actively controlled, mobility of TCTP gene products between shoot and roots modulate root system architecture, and the trade-off between branching or elongating deeper.