It should be stressed that the orthologue gene of SP in Arabidopsis, called TFL1 (for Terminal Flower 1) does not play the same role. "In this model species, TFL1 acts so that the apical meristem does not flower but becomes inflorescential, i.e. it maintains a reserve of stem cells to produce flowers indefinitely", explains  Claire Périlleux.


One question remains unanswered in the scientists' minds: what prevents the tomato plant's stem cells from being used up? If it is not SP, what does play this role in the plant? This is the question which Claire Périlleux and Johanna Thouet, a doctoral student in the ULg's Laboratory of Plant Physiology, try to address, alongside researchers from the Catholic University of Louvain-la-Neuve, in a new article published in the journal PLoS ONE (2). 

The unexpected role of the JOINTLESS gene

"In plant biology, many things have been discovered from the study of mutants" says Claire Périlleux. "Given the agronomical importance of the tomato plant, mutants were obtained not as the result of experimental manipulations but through selection programmes, because they presented interesting characteristics or because they grew well."  This is the case of the Jointless variety. It has the advantage of not having an abscission zone at the fruit peduncle. "This fragile zone allows the fruit to fall when it is ripe, but horticulturalists prefer to pick the fruit directly from the plant" indicates Claire Périlleux.

By taking a closer look, scientists realised that the lack of an abscission zone was not the only ‘abnormality’ which Jointless cultivars presented. "The inflorescence meristems of this mutant produced one, two or three flowers, and then go on to produce more leaves!" says the researcher. "This is an abnormal developmental programme because once a meristem produces an inflorescence, normally it doesn't produce any more leaves".

(2) Thouet, J., Quinet, M., Lutts, S., Kinet, J.-M. and Périlleux, C., 2012. Repression of floral meristem fate is crucial in shaping tomato inflorescence. PLoS ONE 7(2): e31096. doi:10.1371/journal.pone.0031096