Floral evolution in Gesneriaceae
Floral bilateral symmetry is the most important trend for flower shape diversity in 200,000 angiosperm species. Zygomorphy and reversal back to actinomorphy independently evolved multiple times in angiosperm evolution. The genetic basis and the role of selection, however, remain lots of unknown.
Belong to the zygomorphy-dominant order, Lamiales, members of Gesneriaceae consist of mainly zygomorphic flowers but with a few exceptions. Accompanied by variation in the symmetry among different floral organs, i.e. corolla and stamens, making it an ideal system in understanding the evolution of bilateral symmetry and reversal events.
The example of typical types of floral symmetry in Gesneriaceae; Actinomorphy: Conandron ramondioides (苦苣苔); Zygomorphy: Hemiboea bicornuta (角桐草)
The developmental mechanism which controls the floral bilateral symmetry is believed to rely on CYCLOIDEA (CYC), a member of the TCP gene family. Meanwhile, GCYC genes, CYC-like genes in Gesneriaceae, duplicated multiple times in evolutionary history. Three duplication events lead to multiple copies of GCYC ranging from two to four in each species.
During the time in the plant evo-devo lab at National Taiwan Universtiy led by Dr. Chun-Neng Wang, I participated in research of the evolutionary history of GCYC genes. While the mainstream approach in evo-devo is developing a new model system, I started from the perspective of molecular evolution to detected the selective pressures in duplicated GCYC lineages. Then, incorporate the observed shift in selection regime with the expression patterns on floral structures among different species. Combining the two aspects, the aim was to trace back the selective pressure in the evolutionary history and its consequences on floral symmetry.
In the past 3 years, Kuan-Ting Hsin (Ph.D. student at IEEB, NTU) and I have worked on the evolution of GCYC duplicates in the paleotropical clade (Trichosporeae) and resulted in two publication:
More details to come. See publication now.
A simplified genealogy of Gcyc genes in Gesneriaceae. The arrows indicate the major duplication events.