Evolutionary Developmental Biology (Evo-Devo)
Christensen, Ashley , Malcomber, Simon .
Evolution of the SEPALLATA gene lineages, LEAFY HULL STERILE1 (LHS1) and Oryza sativa MADS5 (OsMADS5), and their contribution to the origin of the grass floret.
SEPALLATA (SEP) genes are key transcriptional regulators during inflorescence development where they often act as co-factors with other floral organ identity genes. Duplication events within developmental gene lineages followed by functional partitioning or diversification have likely contributed to the great diversity of flower structures and morphologies. Unlike the flowers of their closest relatives that have two whorls of tepals, most members of the family Poaceae have lemmas and paleae in the outer floral whorls. LEAFY HULL STERILE1 (LHS1), a SEP gene, is a major regulator of lemma development in rice and has been linked to the origin of lemmas and the diversification of the grass spikelet. We are using phylogenetics, comparative RNA expression, and molecular evolutionary analyses to investigate the developmental and evolutionary roles of LHS1. Bayesian phylogenetic analyses indicate that the LHS1 and Oryza sativa MADS5 (OsMADS5) clades were produced from a duplication event at the base of the grass family. Protein sequence alignment indicates that the distinctive C-terminal motif of grass LHS1 genes is also present in closely related graminoid Poales whereas a point mutation in the C-terminus of the OsMADS5 lineage resulted in a premature truncation of the protein product following the LHS1/OsMADS5 duplication event. LHS1 is expressed in the lemmas of all grasses tested to date, but expression in the other floral organs varies from species to species suggesting additional roles in spikelet development. OsMADS5 expression patterns vary from species to species. The LHS1/OsMADS5 precursor in Joinvillea is expressed in the outer and inner tepal whorls, plus the stamen filament. These expression patterns suggest potential subfunctionalization and neofunctionalization in grasses following the LHS1/OsMADS5 duplication event and emphasizes the role LHS1 in combination with other SEP and ABC-like genes might have played in the both the origin of lemmas and the grass spikelet.
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1 - California State University - Long Beach, Biological Sciences, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA
2 - California State University - Long Beach, Biological Sciences, 1250 Bellflower Blvd, Long Beach, California, 90840, USA
Presentation Type: Poster:Posters for Topics
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM