Evolutionary Developmental Biology (Evo-Devo)
Wu, Hsiu-Chung , Su, Huei-Jiun , Hu, Jer-Ming .
The identification of A-, B-, C-, and E-class MADS homologues and the implication of perianth evolution in Trochodendron aralioides (Trochodendraceae).
TROCHODENDRON aralioides is the sole member of the family Trochodendraceae, and has vesselless wood and lacks a perianth, therefore for some time it has been suggested as one of the most primitive angiosperms. Recent phylogenetic analyses place Trochodendron in the basal eudicots and very close to the core eudicots. In 1986, Endress demonstrated that there are a few residual scales located between the prophylls and the stamens of T. aralioides, and called those residue organs “tepals”. Our observations showed that there are more scales appearing serially from prophylls to tepals in our samples than previously reported. Furthermore, we found that the number of scales differs slightly between protandrous and protogynous flowers. The epidermal cells on many floral parts are papillate, similar to the epidermal cells of ordinary showy petals of other species. All together, the results suggest that the perianth of Trochodendron is very likely reduced during evolution and the function of perianth has been replaced by the whole inflorescence as the attracting agent to the pollinators. In order to elucidate the underlying mechanism of floral organ formation, we have identified homologues of floral organ identity genes in T. aralioides. Three B class homologues have been reported by previous studies and we successfully cloned additional one A class, two C class, and four E class homologous genes from T. aralioides. Phylogenetic analysis confirmed these identities and show they are all prior to the major duplication in MADS-box gene lineages. The phylogenetic analysis also supports Trochodendron as a member of basal eudicots based on the identified gene sequences. The RT-PCR expression patterns for those floral identity gene homologues do not match well to the current floral ABCDE model.
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1 - National Taiwan University, Institute of Plant Biology, Rm1227, Life Science Building, 1 Roosevelt Road Sect. 4, Taipei, 106, Taiwan
2 - National Taiwan University, Institute of Ecology and Evolutionary Biology, Rm1227, Life Science Building, 1 Roosevelt Road, Sect.4, Taipei, 106, Taiwan
Presentation Type: Oral Paper:Papers for Topics
Location: 303/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 4:30 PM