Molecular evolution of bearded-ear orthologs in the grass family

ELIZABETH A. KELLOGG; REINHEIMER RENATA

Congreso; 50th Annual Maize Genetics Conference; 2008

Several genes have recently been identified that are involved in the control of floral development and sex determination in maize. Among these, bearded-ear (bde), a MADS-box transcription factor that belongs to the AGL6 clade, is required for floral meristem determinacy, organ identity and carpel abortion in the tassel. Moreover, bde orthologs have been reported to be preferentially expressed in flower tissues in several species more or less closely related to maize. Little is known about the evolution of AGL6-like genes in the grass family and other monocots. Here we report progress in characterization of the evolution of AGL6 orthologs from 27 grass species and 6 species of non-grass monocots. Based on sequence comparisons, the C-terminal region of AGL6-like genes exhibits considerable heterogeneity among grasses, suggesting possible variation in the control of transcriptional activation, gene interactions, DNA binding specificity and/or localization. Interestingly, a glutamine-rich domain in the C-terminal region characterizes the subfamilies Pooideae and Chloridoideae, but is absent in gymnosperms, dicots, other grasses, and non- grass monocots. The preliminary phylogeny for the AGL6-like genes in grasses largely agrees with the species phylogeny. At least three different duplication events were recovered within grasses: a) at the base of the grasses (OsMADS6 and OsMADS17), b) inside the BEP Clade and, c) at the base of Zea and Tripsacum linage (ZAG3 and ZAG5). Despite multiple efforts at PCR with various combinations of primers, we have not detected an OsMADS17-like sequence in grasses other than rice; all sequences recovered so far are homologs of OsMADS6. Our data suggest that perhaps OsMADS17 has been lost inthe grasses