EXPRESSION PATTERNS OF BEARDED-EAR ORTHOLOGS IN THE GRASS FAMILY

REINHEIMER RENATA; ELIZABETH KELLOGG

Chicago

Congreso; 51st Annual Maize Genetics Conference; 2009

ZAG3 (Bearded-ear) is a MADS-box gene of maize orthologous to the AGL6 and AGL13 genes of Arabidopsis. Many studies have shown that AGL6 is primarily a floral specific gene but its role during flower development is unclear in part because its expression pattern varies from one lineage to the next. Some authors have suggested that AGL6-like genes may have an important role in perianth evolution. The zag3 mutant (bearded-ear, bde) produces extra flowers and extra carpels suggesting that ZAG3 is involved in floral meristem determinacy and carpel development. We previously showed that the phylogeny for the ZAG3-like genes in grasses largely agrees with the species 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). Here we present an update of the phylogeny as well as data from mRNA in situ hybridization in distantly related grass species. In situ hybridization showed that ZAG3 orthologs in grasses are expressed initially in floral meristems. Later in development, mRNA was detected in lodicules and in the developing gynoecium, in which it becomes restricted to the inner integument. Expression in stamens was only detected in the basal grasses (i.e. Streptochaeta angustifolia) and in subfamily Ehrhartoideae (i.e. Oryza sativa and Leersia sp.). Expression in the palea was only detected in members of subfamily Panicoideae (i.e. Sorghum bicolor and Setaria italica). OsMADS6 and OsMADS17 showed overlapping expression patterns. These results suggest that ZAG3 may play a general role in the grasses during lodicule and carpel development. In addition, expression in stamens and paleas in some lineages suggests that ZAG3 orthologs have diversified in grasses and may have different roles in different species.