Seedless fruits and the disruption of a conserved genetic pathway in angiosperm ovule development
Abstract
17 Pag., 1 Tabl., 7 Fig. The definitive version is available at: http://www.pnas.org/ ; Although the biological function of fruiting is the production and dissemination of seeds, humans have developed seedless fruits in a number of plant species to facilitate consumption. Here we describe a unique spontaneous seedless mutant (Thai seedless; Ts) of Annona squamosa (sugar apple), a member of the early-divergent magnoliid angiosperm clade. Ovules (seed precursors) of the mutant lack the outer of two normal integuments, a phenocopy of the inner no outer (ino) mutant of Arabidopsis thaliana. Cloning of the INO ortholog from A. squamosa confirmed conservation of the outer integument-specific expression pattern of this gene between the two species. All regions of the gene were detectable in wild-type A. squamosa and in other members of this genus. However, no region of the INO gene could be detected in Ts plants, indicating apparent deletion of the INO locus. These results provide a case of a candidate gene approach revealing the apparent molecular basis of a useful agronomic trait (seedless fruit) in a crop species, and indicate conservation of the role of a critical regulator of ovule development between eudicots and more ancient lineages of angiosperms. The outer integument is one synapomorphy of angiosperms separating them from other extant seed plants, and the results suggest that the evolution of this structure was contemporaneous with the derivation of INO from ancestral YABBY genes. Thus, a unique lateral structure appears to have coevolved with a novel gene family member essential for the structure's formation. ; This work was supported by grants from the Spanish Ministry of Science and Innovation (Project Grants AGL2007- 60130/AGR, AGL2009-12621, and AGL2010-2140), Instituto Nacional de Investigación Agraria y Alimentaria (RF2009-00010), GIE-Aragón 43, Junta de Andalucía (FEDER AGR2742), and the European Union under the INCODEV Program (Contract 015100) and from the US National Science Foundation (IOS-0920618). J.L. was supported by grants from Junta de Andalucía and the National Science Foundation Molecular and Organismic Research in Plant History (MORPH) Network. ; Peer reviewed
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