Insights into Genetics of Floral Development in Amborella trichopoda: Genome-Wide Analysis of MADS-Box Transcription Factors — 40p — Sanam Parajuli, Bibek Adhikari, Madhav Nepal

Department of Biology and Microbiology, South Dakota State University, Brookings, SD, 57007

A general framework of floral development in angiosperms is provided by the ABCDE model that describes floral arrangement in concentric whorls. Underlying genes in the majority of monoecious angiosperms, including the model plant Arabidopsis thaliana, are primarily MADS-Box family members. The roles of these genes in dioecious basal angiosperms, like Amborella trichopoda, which has spirally arranged floral organs, are not clearly understood. A. trichopoda is a dioecious plant with flowers consisting of a perianth, stamens or carpels, depending on the sex, and non-functional and rudimentary forms of male and female organs present in female and male flowers respectively. The major objectives of this study were to perform a genome-wide identification and characterization of MADS-BOX genes in A. trichopoda, and to examine gene expression data to understand their involvement in floral development. We identified 34 members of the MADS-Box gene family in A. trichopoda with Hidden Markov Model-based genome-wide survey. Among them, 22 were classified into Type-II or MIKC group. We found orthologs of B- and C-class floral MADS-Box genes in A. trichopoda. However, ortholog of A. thaliana AGL7 (AP1), an A-class floral MADS-Box gene was absent. Analysis of the gene expression data showed that MIKC-type genes were differentially expressed between male and female flowers with two AP3 (B-function) paralogs-1 and 2, being upregulated in male and female flowers, respectively, and E-function orthologs being upregulated in female flowers. With these observations, we predict that A. trichopoda flowers employ a modification of the classical ABCDE model of floral development where A-function floral MADS-Box gene orthologs are absent, and B-class paralogs work in different reproductive whorls in the different sexes and are not limited to stamen identity, and E-function genes upregulated in female flowers. 

Keywords: Amborella trichopoda, Basal Lineage of Angiosperms, Gene Family,  MADS-Box Transcription Factors, Modified ABCDE Model, Flowering Plants

South Dakota State University
Dr. Madhav Nepal