title: Elaboration of B gene function to include the identity of novel floral organs in the lower eudicot Aquilegia.
abstract: The basal eudicot Aquilegia (columbine) has an unusual floral structure that includes two morphologically distinct whorls of petaloid organs and a clearly differentiated fifth organ type, the staminodium. In this study, we have sought to determine how Aquilegia homologs of the B class genes APETALA3 (AP3) and PISTILLATA (PI) contribute to these novel forms of organ identity. Detailed expression analyses of the three AP3 paralogs and one PI homolog in wild-type and floral homeotic mutant lines reveal complex patterns that suggest that canonical B class function has been elaborated in Aquilegia. Yeast two-hybrid studies demonstrate that the protein products of Aquilegia's AP3 and PI homologs can form heterodimers, much like what has been observed for their core eudicot homologs. Downregulation of AqvPI using virus-induced gene silencing indicates that in addition to petal and stamen identity, this locus is essential to staminodial identity but may not control the identity of the petaloid sepals. Our findings show that preexisting floral organ identity programs can be partitioned and modified to produce additional organ types. In addition, they indicate that some types of petaloid organs are not entirely dependent on AP3/PI homologs for their identity.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA. ekramer@oeb.harvard.edu
authors.forename: Elena M
authors.initials: EM
authors.lastname: Kramer
authors.forename: Lynn
authors.initials: L
authors.lastname: Holappa
authors.forename: Billie
authors.initials: B
authors.lastname: Gould
authors.forename: M Alejandra
authors.initials: MA
authors.lastname: Jaramillo
authors.forename: Dimitriy
authors.initials: D
authors.lastname: Setnikov
authors.forename: Philip M
authors.initials: PM
authors.lastname: Santiago
mesh_terms: D031884:Aquilegia / Q000033:anatomy & histology* / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D035264:Flowers / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D017403:In Situ Hybridization; D018519:Meristem / Q000166:cytology; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger