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Plant development and evolution: Lessons learned from candidate genes

Litt, Amy [1], Irish, Vivian F. [1].

Evolutionary changes in a MADS-box gene lineage: implications for the evolution of floral development mechanisms.

Plant MADS-box genes play key roles in a variety of processes, including embryo development, determination of flowering time, specification of floral meristem and floral organ identity, and fruit development. Phylogenetic analyses of angiosperm MADS-box genes suggest that this gene family has undergone multiple duplication and sequence divergence events that may have had significant impact on floral evolution. To better understand the timing and the potential significance of these events, we are focusing on the APETALA1/FRUITFULL-like (AP1/FUL-like) MADS-box gene group. Our phylogenetic analyses of AP1/FUL-like genes from a wide variety of angiosperms show two major gene clades, euAP1 and euFUL, within the core eudicots. Non-core eudicot species have only sequences similar to euFUL genes (FUL-like) and lack euAP1-like genes. The predicted protein products of all euFUL and FUL-like genes share a highly conserved C-terminal amino acid motif. In contrast, predicted products of members of the euAP1 clade contain a different C-terminus, possibly evolved through a frameshift mutation, that includes new functional domains. Arabidopsis AP1, a member of the euAP1 clade, is a key regulator of floral development and is implicated in specifying perianth identity (the A function of the ABC model). However, the presence of euAP1 genes only in core eudicots suggests that this role may be unique within core eudicots, and that A function as such may not be conserved across angiosperms. Current experiments aimed at determining the role of the different amino acid motifs suggest that the euAP1 motifs confer new functions, distinguishing those proteins functionally from euFUL and FUL-like proteins. Expression studies of euAP1, euFUL, and FUL-like genes suggest that the ancestral functions of this lineage may be in meristem identity and fruit development. Together this evidence suggests that the molecular mechanisms underlying floral development have undergone significant changes during angiosperm evolution.

1 - Yale University, Molecular, Cellular, and Developmental Biology, P.O. Box 208104, New Haven, Connecticut, 06520-8104, USA

MADS-box genes
floral development
gene phylogeny
ABC model.

Presentation Type: Symposium
Session: 44-5
Location: Ballroom 1 (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 10:30 AM
Abstract ID:673

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