MADS-BOX GENES: DEFINING THE SPECIALIZED STRUCTURES OF ORCHID FLOWERS

摘要

The complex flower organization of orchids offers an opportunity to discover new variant genes and different levels of complexity in the morphogenesis of flowers. Orchids have unique flowers involving three types of perianth organs: outer tepals, lateral inner tepals, and a lip. Gene duplications substantially contributed to the origin of morphological novelties during evolution in plants. Neo-functionalization might result in key innovations such as the floral lip that enable adaptive radiations such as those of orchids. The zygomorphic orchid flower, with its remarkable lip, might serve as a model system for further studies. Expression studies indicated that the identity of tepals and lips is specified by the combinatorial interaction of four different DEFICIENS-like MADS-bpx genes. Evolution of these genes provides a rational framework for reconstructing the enigmatic origin and unique diversification of the orchid flower. PeMADS5, a DEF-like MADS-box, gene is important for initiation of stamensbut not necessary for later organogenesis of pollinia.