Developmental origins of the world's largest flowers, Rafflesiaceae

Area of Science:

• Plant biology
• Evolutionary developmental biology
• Botany

Background:

• Rafflesiaceae are known for the world's largest flowers, but their floral organ development is poorly understood.
• Most species feature a diaphragm creating a floral chamber for pollination by carrion flies.

Purpose of the Study:

• To investigate the homology of floral organs in Rafflesiaceae, specifically comparing Rafflesia and Sapria.
• To understand the developmental basis of the floral chamber morphology in these holoparasitic plants.

Main Methods:

• Comparative studies of floral structure and development.
• Analysis of gene-expression patterns.
• Investigating developmental repatterning in Rafflesia.

Main Results:

• The floral chambers of Rafflesia and Sapria are not homologous, despite superficial similarities.
• In Rafflesia, the diaphragm originates from the petal whorl.
• In Sapria, the diaphragm arises from a unique ring structure, a potential Rafflesiaceae synapomorphy.

Conclusions:

• The floral chamber morphology in Rafflesia and Sapria represents two independent evolutionary derivations.
• Developmental repatterning in Rafflesia may have facilitated secondary increases in floral size.