The MADS-box genes involved in the development of orchid flowers.

Since the advent of Darwinian genetics, there has been much interest in the evolutionary origin of the Orchidaceae, one of the most species-rich angiosperm families. Orchids have highly diversified and specialized flowers, and some species exhibit an uncoupled rate of morphological and molecular evolution. Recently, these peculiar characteristics have enhanced the study of the orchid MADS-box genes involved in flower development. This large gene family encodes transcription factors that constitute the main regulatory network driving the formation of flower organs. Recent analyses have highlighted the role of the MADS-box genes in orchids and shown that different evolutionary forces act on the coding and non-coding regions of these genes. The most widely accepted theory proposed to explain the evolution of the orchid perianth is the “orchid code”, which posits that the orchid floral organs became diversified through a series of duplications and mutations of the MADS-box genes, followed by functional diversification.