EVOLUTION AND EXPRESSION PATTERNS OF AGL6-like genes IN POALES

REINHEIMER RENATA; ELIZABETH A. KELLOGG

Vancouver

Congreso; Botany 2008; 2008

MADS-box genes encode transcription factors that control the development of plants, animals, fungi and even human. Some plant MADS-box genes, such as AGAMOUS (AG) from Arabidopsis, work as organ identity genes conferring identity to stamens and carpels during flower development. Several genes that share sequence similarity with AG have been isolated. Among those, AGAMOUS-like 6 (AGL6) in Arabidopsis is expressed preferentially in flower, although its function in Arabidopsis is unknown. The related gene in maize, ZAG3, plays important roles in floral meristem determinacy and carpel development. In order to understand the evolution and the role of AGL6-like proteins in floral development in Poales, we have reconstructed their phylogeny and analyzed expression patterns. The phylogeny of the genes is consistent with the organismal phylogeny. Two different duplication events were discovered: a) around the base of the grasses, leading to two paralogous clades (OsMADS6 and OsMADS17), and b) in Zea and Tripsacum (ZAG3 and ZAG5). Despite multiple efforts at PCR and sequencing of multiple clones, we did not detect an OsMADS17-like sequence in grasses other than rice; all sequences were homologs of OsMADS6. Furthermore, lack of an OsMADS17 homolog in the maize genome suggests the possibility of gene loss within grasses. AGL6 homologs are expressed only in flowers. In non-grass monocots, they are expressed preferentially in first and second whorl structures and carpels. In grasses the genes are (1) not expressed in glumes; (2) restricted to florets with stamens or a gynoecium or both; and (3) not expressed in florets that consist only of a lemma (i.e. are sterile).