Flowering plant diversity is regarded as a striking example of rapid radiation. Hypotheses to explain the evolutionary success of flowering plants consider the role of plant-animal interactions mediated by the flower. Using a candidate gene approach, this proposal will test for the function of MADS box genes, known to be responsible for flower development, in the evolution of floral form. We focus on the Zingiberales, a lineage of tropical plants including bananas and gingers, containing a diversity of floral forms associated with efficient pollination. Also, this research will isolate candidate MADS box genes from Zingiberales species and examine their expression temporally and spatially to characterize the gene networks underlying flower development and evolution. Genome sequences for Musa and transcriptome (RNA-Seq) data from across Zingiberales will be used to investigate additional genes responsible for the evolution of flowers.
This research contributes to multi-disciplinary training of graduate and undergraduate students in evolutionary biology, developmental genetics, and plant morphology. Results will be presented at national and international scientific meetings and as peer-reviewed publications. A better understanding of the gene networks underlying evolution of flowers will benefit other research studying non-model flowering plants and may prove helpful for agricultural research in Musa acuminata (banana), Zingiber officinale (ginger), Cucurma longa (turmeric), Elettaria sp. (Cardamom) and the improvement of horticultural cultivars.
Why are there so many different flowers? How do these floral forms evolve through time? What are the genetic and evolutionary processes underlying diversity of forms we see in plants? These are just some of the fundamental questions concerning developmental evolution of floral diversity that this proposal contributed to answering. In general terms, one major results of this research was the generation of data support the hypothesis that evolution repeatedly uses a few basic mechanisms in order to shape different parts of the plant, a process referred to as â€˜co-optionâ€™. In the case of the Zingiberales, we show that the morphological evolution of the male floral organs (stamens) utilizes similar developmental mechanisms to those used to shape leaf form. However, the evolution of morphological diversity is not always as simple as understanding basic genetic mechanisms from model systems. Research supported by this grant also helped to uncover the intricacies of the effect of gene duplications and divergence of B-class and C-class MADS-box genes; these genes were known to be necessary for the proper development of many floral organs, such as petals and reproductive organs, but were shown to also be involved in the morphologies of these organs and their diversification. In particular, Zingiberales specific gene duplications are observed in both B- and C-class lineages, and positive selection can be detected in protein residues that might influence protein function. These results led us to propose innovative mechanisms that could explain the morphological variation observed in the ginger flowers. Results from of this funded research were presented at national and international scientific meetings and resulted in invited and award-winning presentations. In 2013 co-PI Almeida was awarded the Agnes Arber Best Student Paper Award at the 5th International Conference on Comparative Biology of Monocotyledons (Monocots V). In 2012 co-PI Almeida was selected to participate in the competitive Ernst Mayr symposium at the annual Evolution meetings. The main findings funded by this award have been published in important scientific journals and presented as part of symposia focusing on novel bioinformatic approaches at the EuroEvoDevo meetings in 2012 and 2014. Broader impacts include the training of 4 undergraduates in plant evodevo and 2 fellow graduate students in bioinformatics and next generation sequencing approaches. Through the training and academic knowledge generated by this award, co-PI Almeida actively contributes to the dissemination of EvoDevo research in Brazil, her home country, and continues to collaborate with PI Specht. Based on the dissertation supported by this grant, co-PI Almeida obtained her PhD in Plant Biology from UC Berkeley and is now a postdoctoral researcher at the Graduate Program in Genetics and Biodiversity from the Federal University of Bahia, Brazil.