Molecular analyses of MADS-box genes trace back to Gymnosperms the invention of fleshy fruits

Botanical fruits derive from ovaries and their most important function is to favor seed dispersal. Fleshy fruits do so byattracting frugivorous animals that disperse seeds together with their own excrements (endozoochory). Gymnospermsmake seeds but have no ovaries to be transformed into fruits. Many species surround their seeds with fleshy structures anduse endozoochory to disperse them. Such structures are functionally fruits and can derive from different anatomical parts.Ginkgo biloba and Taxus baccata fruit-like structures differ in their anatomical origin since the outer seed integumentbecomes fleshy in Ginkgo, whereas in Taxus, the fleshy aril is formed de novo. The ripening characteristics are different,with Ginkgo more rudimentary and Taxus more similar to angiosperm fruits. MADS-box genes are known to be necessaryfor the formation of flowers and fruits in Angiosperms but also for making both male and female reproductive structuresin Gymnosperms. Here, a series of different MADS-box genes have been shown for the first time to be involved also in theformation of gymnosperm fruit-like structures. Apparently, the same gene types have been recruited in phylogeneticallydistant species to make fleshy structures that also have different anatomical origins. This finding indicates that the mainmolecular networks operating in the development of fleshy fruits have independently appeared in distantly relatedGymnosperm taxa. Hence, the appearance of the seed habit and the accompanying necessity of seed dispersal has led tothe invention of the fruit habit that thus seems to have appeared independently of the presence of flowers