Systems biology of sink strength: mechanistic understanding of regulation and adaptation of tomato fruit sink strength

Knowledge and understanding of plant physiology and genetics is rapidly moving forward. However integration of these advances with the extensive experimental work on effects of environmental factors on organ and plant growth and development is limited.

Especially, with respect to so-called ‘sinks’ (growing and developing organs) this integration is lacking. Since the harvestable organs are often the major sinks, this lack of integration represents a bottleneck for improvements in crop biomass distribution towards the harvestable parts. Studies on tomato fruit growth and development at WUR-PSG have generated many datasets for transcriptomics, metabolomics, cell division and tissue growth, and fruit growth and competition between organs at various developmental stages from pre-anthesis to ripening. We propose to combine these datasets with mechanistic modelling to integrate physiological and genetic knowledge on tomato fruit sink strength (i.e. potential growth rate) as well as interactions with environmental factors, by focusing on the central question:

To what extent is tomato fruit sink strength determined by the developmental, genetic program of cell and tissue formation, and how much control is exerted by environmental factors during growth?

A mechanistic modelling approach is proposed, which captures the integrated behavior of cell division and endoreduplication, cell and tissue expansion, as well as transport and influences of sucrose and auxin (which combine these processes with organ sink strength and resulting growth and competition at plant scale) as a function of environmental conditions. The model will also be used to evaluate current existing dogmas on control exerted by either low integration levels (i.e. fruit growth is an emerging property of underlying processes) or the higher integration levels (i.e. fruit growth is coordinated by transcriptional networks at organ level, cell division is a consequence rather than a cause of growth).