Abstract

Biological systems exhibit a spontaneous emergence of order, or self‐organization, resulting in the establishment of complex patterns of cell types. Organs regeneration is a paramount example of post‐embryonic pattern reorganization, and plants are ideal model systems for investigating this high level of developmental plasticity.

I have previously established a novel system for studying in vivo plant organs regeneration, by showing that the root apex of the model organism Arabidopsis thaliana grows back when completely excised. Cell division provides the main source of pattern modification in this system due to the anchoring effect of cell walls and consequent absence of cell migration. Surprisingly, however, root regeneration does not require a functional stem cell niche, an observation that opens fundamental questions on the mechanisms that lead to de novo re‐patterning.

Any attempt to further improve our understanding of self‐organization in multicellular systems requires a quantitative analysis of its morphological dynamics at the cellular level, coupled with an abstract model of the underlying interactions. Moreover, tissue reorganization during regeneration is a highly dynamical process which cannot be fully understood by sporadic observation and still images. Instead, long (days) time‐lapse observations at high spatial (microns) and temporal (minutes) resolutions are required to capture the full cellular dynamics. Due to its almost complete transparency, and the limited number and highly symmetric organization of its tissues, the Arabidopsis root is a valuable model system for the experimental investigation of patterning and self‐organization.

Unfortunately, ensuring continuous specimen access, while preserving physiological conditions and preventing photo‐damage, poses major barriers to measurements of cellular dynamics in indeterminately growing organs such as plant roots. Furthermore, commercially available platforms for time‐lapse microscopy are unsuitable to sustain a live plant on stage for many days with a vertically growing root.

To overcome these technical obstacles, I have led the development of a unique imaging system that integrates optical sectioning through light sheet fluorescence microscopy with hydroponic culture. The system has been adapted to perform 3D fluorescence optical sectioning at cellular resolution of a vertically growing Arabidopsis root, every few minutes and for many consecutive days. Novel automated routines have been developed to track the root tip as it grows, track cellular nuclei and identify cell divisions.

I will discuss the experimental and computational advantages to use plant organs regeneration to study the phenomenon of self‐organization in biology. I will present the state‐of‐the art on Arabidopsis root regeneration and introduce the newly developed imaging setup and recent quantitative data collected from a growing root. The requirements for future computational modelling approaches in multicellular self‐organizing systems will be discussed.