Duplication and diversification of the <it>LEAFY HULL STERILE1 and Oryza sativa MADS5 SEPALLATA </it>lineages in graminoid Poales

• Main Authors: Christensen Ashley R, Malcomber Simon T
• Format: Article
• Language: English
• Published: BMC 2012-02-01
• Series: EvoDevo
• Subjects: grasses; <it>LHS1</it>; MADS-box; <it>OsMADS5</it>; Poaceae; neofunctionalization; subfunctionalization
• Online Access: http://www.evodevojournal.com/content/3/1/4

<p>Abstract</p> <p>Background</p> <p>Gene duplication and the subsequent divergence in function of the resulting paralogs via subfunctionalization and/or neofunctionalization is hypothesized to have played a major role in the evolution of plant form. The <it>LEAFY HULL STERILE1 (LHS1) SEPALLATA </it>(<it>SEP</it>) genes have been linked with the origin and diversification of the grass spikelet, but it is uncertain 1) when the duplication event that produced the <it>LHS1 </it>clade and its paralogous lineage <it>Oryza sativa MADS5 (OSM5) </it>occurred, and 2) how changes in gene structure and/or expression might have contributed to subfunctionalization and/or neofunctionalization in the two lineages.</p> <p>Methods</p> <p>Phylogenetic relationships among 84 <it>SEP </it>genes were estimated using Bayesian methods. RNA expression patterns were inferred using <it>in situ </it>hybridization. The patterns of protein sequence and RNA expression evolution were reconstructed using maximum parsimony (MP) and maximum likelihood (ML) methods, respectively.</p> <p>Results</p> <p>Phylogenetic analyses mapped the <it>LHS1/OSM5 </it>duplication event to the base of the grass family. MP character reconstructions estimated a change from cytosine to thymine in the first codon position of the first amino acid after the <it>Zea mays MADS3 </it>(<it>ZMM3</it>) domain converted a glutamine to a stop codon in the <it>OSM5 </it>ancestor following the <it>LHS1/OSM5 </it>duplication event. RNA expression analyses of <it>OSM5 </it>co-orthologs in <it>Avena sativa, Chasmanthium latifolium, Hordeum vulgare, Pennisetum glaucum</it>, and <it>Sorghum bicolor </it>followed by ML reconstructions of these data and previously published analyses estimated a complex pattern of gain and loss of <it>LHS1 </it>and <it>OSM5 </it>expression in different floral organs and different flowers within the spikelet or inflorescence.</p> <p>Conclusions</p> <p>Previous authors have reported that rice OSM5 and LHS1 proteins have different interaction partners indicating that the truncation of OSM5 following the <it>LHS1/OSM5 </it>duplication event has resulted in both partitioned and potentially novel gene functions. The complex pattern of <it>OSM5 </it>and <it>LHS1 </it>expression evolution is not consistent with a simple subfunctionalization model following the gene duplication event, but there is evidence of recent partitioning of <it>OSM5 </it>and <it>LHS1 </it>expression within different floral organs of <it>A. sativa, C. latifolium, P. glaucum </it>and <it>S. bicolor</it>, and between the upper and lower florets of the two-flowered maize spikelet.</p>