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Expression of Floral MADS‐Box Genes in Two Divergent Water Lilies: Nymphaeales and Nelumbo

2010; University of Chicago Press; Volume: 171; Issue: 2 Linguagem: Inglês

10.1086/648986

1537-5315

Mi‐Jeong Yoo, Pamela S. Soltis, Pamela S. Soltis,

Plant Diversity and Evolution

To provide insights into the floral developmental genetics of Nymphaeales (water lilies), we investigated the expression patterns of floral organ identity genes in three genera: Cabomba, Nuphar, and Nymphaea. Additionally, because of the superficial floral similarity between Nymphaea and the early‐diverging eudicot Nelumbo, we conducted the same experiments in the latter taxon. We focused on gene expression associated with (1) perianth differentiation in Nymphaeales, (2) the transition of petaloid staminodes to stamens in Nymphaea, and (3) organ identity in Nymphaea and Nelumbo. In Cabomba, the expression patterns of B‐class gene homologues fit the "sliding boundaries" model, with B‐class gene expression in sepals and petals. In contrast, Nuphar and Nymphaea exhibit broad B‐class gene expression that extends across all floral organs (i.e., "fading borders" model). The gene expression patterns observed suggest that the innermost petals of Nymphaea originated from petaloid staminodes. Also, despite the morphological differences between flowers of Nymphaea and Nelumbo and the phylogenetic distance between these genera, floral gene expression patterns are nearly identical. Last, we infer that either the "out‐of‐male" hypothesis or the "mostly male" hypothesis, both of which specify derivation of floral parts from male structures, might apply to the ancestors of Nymphaeales.