In the context of their new study, Claire Périlleux and her colleagues created a series of double mutants to understand the role of these genes and how they interact to regulate the formation of inflorescence in tomato plants. "The most interesting and unexpected result that we have seen concerns a double mutant involving the JOINTLESS gene" she reveals. "When a mutation of this gene is combined with a mutation of the Single Flower Truss (SFT) gene, the tomato plant forms a terminal flower, exactly as when the TFL1 is mutated in Arabidopsis!"


These results show that the JOINTLESS gene is involved in maintaining the stem cells necessary for the tomato's inflorescence development. But it does not act alone: "It is likely to be the result of a complex interaction between different genes including Single Flower Truss which encodes the mobile protein FT" (see the article : The Cocktail of a Flowering).

How many flowers per inflorescence?

The scientists then looked at where the JOINTLESS gene was expressed in order to see whether this was coherent with the role which they had proposed. "This gene is only expressed in the part of the inflorescential meristem which remains undifferentiated, i.e. the part which does not become a flower" reveals Claire Périlleux. This expression pattern confirms that JOINTLESS is involved in the maintenance of stem cells within this type of meristem. According to the researcher, JOINTLESS acts as an inhibitor of another gene, called FALSIFLORA, which is required for the formation of the flower.

In fact, the mutation of the Single Flower Truss gene alone sometimes provokes the appearance of a terminal flower, but not always. "The double mutant jointless x single flower truss, enables a strict and reproducible phenotype to be obtained" specifies Claire Périlleux. "The mobile protein encoded by SFT moves from the leaves of the plant to the inflorescence meristem, where it activates genes which, in combination with JOINTLESS, control the number of flowers which the inflorescence will initiate". This new information may be valuable to the horticultural world, as the number of fruits produced by a tomato plant depends directly on the number of flowers previously formed.

These results have already attracted the attention of a Dutch company which wishes to use them to model tomato flowering in order to make predictions.  Could this be the start of a flourishing  collaboration?