Almeida, Ana Maria , Yockteng, Roxana , Freeling, Michael , Specht, Chelsea .
The evolution ofZingiberales petaloid staminodes through ab-ad polarity lenses: Implications for plant body plan evolution.
The molecular mechanisms of abaxial-adaxial (ab-ad) polarity in plants have been well studied as a property of flattened organs, like leaves. Antirrhinum majus andArabidopsis thaliana mutants with radialized leaves - in place of the wildtype, laminar structures - allowed for the description of a complex underlying gene network for the establishment of ab-ad polarity. Most importantly, specification of ab-ad identity is tightly linked to final organ shape â€“whether an organ will develop into a cylindrical or a flattened structure. Laminar expansion takes place at the domain of interaction between abaxializing and adaxializing agents, in the presence of balanced ab-ad gene expression. Over or under expression of either abaxializing or adaxializing genes inhibits laminar growth, resulting in a mutant radialized phenotype. In the Zingiberales, an order of tropical monocots, the evolution of androecial morphology is characterized by a marked reduction in the number of fertile stamens and their replacement by infertile stamens (staminodes) that are flattened, petaloid structures. We hypothesize that the evolution of petaloidy in this group is tightly linked to the co-option of the leaf ab-ad gene network acting on the filament of the petaloid staminodes. Transcriptome data from Costus spicatus and Musa acuminata filaments show a 10-fold overexpression of Arabidopsis thaliana YABBY2/5 ortholog in Musa acuminata when compared to Costus spicatus filament transcriptome. To further test our hypothesis, filament transcriptome of Brassica rapa - an eudicot rosid from the order Brassicales - was generated. Ab-ad polarity gene expression in Brassica rapa filament agrees with that found in Musa acuminata, providing further evidence for the involvement of the ab-ad polarity network in filament morphology. Disruption of a balanced ab-ad gene expression in the filament inhibits laminar growth, resulting in a cylindrical, radially symmetrical structure. Here, we argue that the co-option of the leaf ab-ad polarity network is an important feature of filament morphology across angiosperms; the angiosperm filament is an abaxialized structure, equivalent to the radialized leaf of an ab-ad polarity mutant. Overall, our results suggest that the polarity gene network is one of the fundamental principals shaping plant form.
1 - University Of California Berkeley, Plant And Microbial Biology, 111 Koshland Hall, Berkeley, CA, 94702, USA
2 - University California, Berkeley, PMB, Specht Lab, 431 Koshland Hall, Berkeley, CA, 94720, USA
3 - University Of California Berkeley, Department Of Plant Biology, 111 KOSHLAND HALL, Berkeley, CA, 94720-3102, USA
4 - University Of California Berkeley, 111 Koshland Hall, MC 3102, Berkeley, CA, 94720, USA
Presentation Type: Regular Oral Presentation
Location: Rendezvous A/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 10:30 AM
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation