The MADS and the Beauty: Genes Involved in the Development of Orchid Flowers

Abstract

Since the time of Darwin, biologists have studied the origin and evolution of the Orchidaceae, one of the largest families of flowering plants. In the last two decades, the extreme diversity and specialization of floral morphology and the uncoupled rate of morphological and molecular evolution that have been observed in some orchid species have spurred interest in the study of the genes involved in flower development in this plant family. As part of the complex network of regulatory genes driving the formation of flower organs, the MADS-box represents the most studied gene family, both from functional and evolutionary perspectives. Despite the absence of a published genome for orchids, comparative genetic analyses are clarifying the functional role and the evolutionary pattern of the MADS-box genes in orchids. Various evolutionary forces act on the MADS-box genes in orchids, such as diffuse purifying selection and the relaxation of selective constraints, which sometimes reveals a heterogeneous selective pattern of the coding and non-coding regions. The emerging theory regarding the evolution of floral diversity in orchids proposes that the diversification of the orchid perianth was a consequence of duplication events and changes in the regulatory regions of the MADS-box genes, followed by sub- and neo-functionalization. This specific developmental-genetic code is termed the “orchid code.”

Improved Postharvest Quality of Inflorescences of fbp1::etr1-1 Transgenic Burrageara ‘Stefan Isler Lava Flow’

“…3), and the labellum (Mondragon-Palomino and Theißen 2009). Like in tulips, class B MADS box gene expression expanded from whorls 2 and 3 (petals and stamens in the dicot models Antirrhinum and Arabidopsis) to whorls 1 and 4 (sepals and carpels) in orchid flowers (Aceto and Gaudio 2011). Thus, the expression of fbp1::etr1-1 in Burrageara flower organs of the first and second whorl which was shown in our expression analysis (Fig.…”

Studies on Oberonia 3. Aberrant flowers and other floral modifications in the orchid genus Oberonia

“…Gynostemium formation is known to be under genetic control of homeotic MADS-box genes, specifically the MIKC C genes (Aceto and Gaudio 2011). It is the basis of the ABCDE model of genetic control of flower development developed in the Arabidopsis model.…”

“…The specific expression of floral organs is controlled by so-called floral quartets of proteins. It must be noted, that amongst the MADS genes identified in orchids (Aceto and Gaudio 2011: their Table 1, their Fig. 5), none are exclusively associated with gynostemium formation.…”

Fibonacci, quasicrystals and the beauty of flowers

“…Interestingly, recent research on orchids has focused on how selective pressures appear to be relaxed thus enabling the extreme morphologies which appear in flowers. 20 Thus aesthetic selection appears to have a similar effect on natural selection in flowers to sexual selection in animals where magnificent structures such as a peacock's tail or a lion's mane develop.…”