Evolution of flower shape in Plantago lanceolata
Plantago lanceolata produces small actinomorphic (radially symmetric), wind-pollinated flowers that have evolved from a zygomorphic, biotically pollinated ancestral state. To understand the developmental mechanisms that might underlie this change in flower shape, and associated change in pollination syndrome, we analyzed the role of CYC-like genes in P. lanceolata. Related zygomorphic species have two CYC-like genes that are expressed asymmetrically in the dorsal region of young floral meristems and in developing flowers, where they affect the rate of development of dorsal petals and stamens. Plantago has a single CYC-like gene (PlCYC) that is not expressed in early floral meristems and there is no apparent asymmetry in the pattern of PlCYC expression during later flower development. Thus, the evolution of actinomorphy in Plantago correlates with loss of dorsal-specific CYC-like gene function. PlCYC is expressed in the inflorescence stem, in pedicels, and relatively late in stamen development, suggesting a novel role for PlCYC in compacting the inflorescence and retarding stamen elongation in this wind pollinated species.
KeywordsPlantago Flower shape Protogyny Wind pollination CYCLOIDEA
We thank Gwyneth Ingram, Justin Goodrich and Andrew Hudson for all their help with the in situ hybridizations, William Thompson for help with the initial amino acid alignment, Benjamin Pommerrenig for recommending the Fructose 1-6 bisphosphate aldolase primers for RT-PCR, Andrew Hudson, Dick Olmstead and Brenda Malloy for critical comments on the manuscript, Ica Dix for help with photography, and David Rawlinson for artwork. We acknowledge the SFI/HEA Irish Centre for High-End Computing (ICHEC) for the provision of computational facilities and support. This work was funded by a Basic Science Research Grant from Enterprise Ireland (JN).
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