Expression Analysis of Floral Symmetry Candidate Genes in Browallia speciosa

Abstract

Stamen structure and development is one of the deciding factors for an angiosperm’s pollination syndrome. The Solanaceae hold particular interest in understanding pollination and stamen relationships due to their development of bilateral symmetry (zygomorphy), and visitation by a variety of pollinators. Previous studies have implied that floral symmetries of the Solanaceae are not solely determined by CYC2-like genes, particularly regarding the zygomorphic corolla. This is unusual, as CYC2-like genes and their homologs have been found to control the floral symmetry in a majority of studied angiosperms, especially in core eudicots. Browallia speciosa Hook. is a particularly interesting organism due to its three different types of stamens, whose structures aid a unique pollination process. This project aims to investigate the molecular basis for the development of different floral organs and bilateral symmetry of B. speciosa. To achieve this, RNA-seq data was analyzed to explore differential gene expression across 5 different floral organs of B. speciosa, and the candidate genes that are likely responsible for its symmetry and floral organ development were identified. Analysis of Browallia speciosa’s de novo transcriptome revealed differential expression of TCP-like transcription factors, along with ANT-like, BOP-like, JAG-like, PAN-like, RBE-like, and ARGOS-like genes. Along with this, gene ontology enrichment analyses highlighted fruit ripening, lipid metabolism, and secondary metabolite synthesis pathways as promising novel avenues for understanding floral symmetry and reproduction. In the future, these results may serve as the basis for functional and molecular studies to confirm the functions of these master genes, and to investigate their downstream regulations. As the molecular comprehension of floral symmetry and pollination expands, we are able to make more informed decisions regarding the stewardship of consequential crops and plants