Evidence for the involvement of GLOBOSA-like gene duplications and expression divergence in the evolution of floral morphology in the Zingiberales

P>The MADS box transcription factor family has long been identified as an important contributor to the control of floral development. It is often hypothesized that the evolution of floral development across angiosperms and within specific lineages may occur as a result of duplication, functional diversification, and changes in regulation of MADS box genes. Here we examine the role of GLOBOSA (GLO)-like genes, members of the B-class MADS box gene lineage, in the evolution of floral development within the monocot order Zingiberales. We assessed changes in perianth and stamen whorl morphology in a phylogenetic framework. We identified GLO homologs (ZinGLO1-4) from 50 Zingiberales species and investigated the evolution of this gene lineage. Expression of two GLO homologs was assessed in Costus spicatus and Musa basjoo. Based on the phylogenetic data and expression results, we propose several family-specific losses and gains of GLO homologs that appear to be associated with key morphological changes. The GLO-like gene lineage has diversified concomitant with the evolution of the dimorphic perianth and the staminodial labellum. Duplications and expression divergence within the GLO-like gene lineage may have played a role in floral diversification in the Zingiberales.