title: Gymnosperm B-sister genes may be involved in ovule/seed development and, in some species, in the growth of fleshy fruit-like structures.
abstract: OBJECTIVE
  The evolution of seeds together with the mechanisms related to their dispersal into the environment represented a turning point in the evolution of plants. Seeds are produced by gymnosperms and angiosperms but only the latter have an ovary to be transformed into a fruit. Yet some gymnosperms produce fleshy structures attractive to animals, thus behaving like fruits from a functional point of view. The aim of this work is to increase our knowledge of possible mechanisms common to the development of both gymnosperm and angiosperm fruits.
  
  
  METHODS
  B-sister genes from two gymnosperms (Ginkgo biloba and Taxus baccata) were isolated and studied. The Ginkgo gene was also functionally characterized by ectopically expressing it in tobacco.
  
  
  RESULTS
  In Ginkgo the fleshy structure derives from the outer seed integument and the B-sister gene is involved in its growth. In Taxus the fleshy structure is formed de novo as an outgrowth of the ovule peduncle, and the B-sister gene is not involved in this growth. In transgenic tobacco the Ginkgo gene has a positive role in tissue growth and confirms its importance in ovule/seed development.
  
  
  CONCLUSIONS
  This study suggests that B-sister genes have a main function in ovule/seed development and a subsidiary role in the formation of fleshy fruit-like structures when the latter have an ovular origin, as occurs in Ginkgo. Thus, the 'fruit function' of B-sister genes is quite old, already being present in Gymnosperms as ancient as Ginkgoales, and is also present in Angiosperms where a B-sister gene has been shown to be involved in the formation of the Arabidopsis fruit.
authors.affiliation: Department of Biology, University of Padua, 35131 Padua, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lovisetto
authors.forename: Flavia
authors.initials: F
authors.lastname: Guzzo
authors.forename: Nicola
authors.initials: N
authors.lastname: Busatto
authors.forename: Giorgio
authors.initials: G
authors.lastname: Casadoro
mesh_terms: D017343:Genes, Plant; D020441:Ginkgo biloba / Q000235:genetics*; D056771:Ovule / Q000235:genetics* / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000254:growth & development; D058614:Seed Dispersal; D012639:Seeds / Q000235:genetics* / Q000254:growth & development; D020946:Taxus / Q000235:genetics*; D014026:Nicotiana / Q000235:genetics
keywords: B-sister gene; Ginkgo biloba; MADS-box genes; Taxus baccata; fruit growth; fruit-like structure