Meeting Abstract
Gene duplication plays a decisive role in organismal diversification and the appearance of novel structures. One of these novel structures are the ovules/seeds which have unique morphological characteristics across seed plants. The genetic mechanisms regulating ovule development have been identified in Arabidopsis thaliana. The initiation of the ovule development appears to be mainly controlled by SEEDSTICK, BEL1 and AINTEGUMENTA. The Arabidopsis ovule has two integuments covering the nucellus. The asymmetric growth of the outer integument reorients the ovule resulting in an anatropous orientation. While BEL1 establishes the initiation of the integument development, INNER NO OUTER (INO), KANADI1 and 2 (KAN1/2) act in the proper development of the outer integument and ABERRANT TESTA SHAPE (ATS/KANADI4), is involved in outer integument development and the proper separation of both integuments. UNICORN (UCN), acts in the outer integument, repressing ATS. SHORT INTEGUMENTS1 (SIN1) is involved in cell elongation of both integuments and the sin1 mutant integuments do not cover the nucellus. We made a comprehensive search of these genes involved in the correct morphological development of the integuments to assess large scale duplications in addition, to expression analyses in the gymnosperm Ginkgo biloba. Our results show that each of these genes has undergone a different evolutionary history across seed plants and that the expression patterns are not conserved between Arabidopsis and Ginkgo. Our results suggest that the integument development network is not conserved between angiosperms and gymnosperms. We analyze the possible impact of these results on the morphological evolution of ovules as well as on the evolution of major seed plant lineages.
