Domestication of plants is often thought to apply principally to food crops, but cultivation has also been widely used to enhance the beauty of ornamental plants. Writing in Nature Plants [attached], authors report the genome sequences of two progenitor species of Petunia hybrida––a plant that has been domesticated exclusively for the beauty of its flowers. These genomes are a notable addition to the known sequences of members of the nightshade family (Solanaceae), because they will enable researchers to unravel fundamental mechanisms in evolution, ecology and gene function. This will help to bring closer an understanding of relationships between plant genomes.
Petunia is used as a model organism, but one might nonetheless wonder why the genome of a popular flower is of interest. With global consumption of floriculture products estimated to be worth around US$30 billion per year, however, much research is aimed at optimizing productivity, flower shape, colour, vase-life, and fragrance. Previous studies have identified many of the genes influencing Petunia flower characteristics, highlighting both the evolutionary conservation and diversification of function between different ornamental varieties. Bombarely et al. [attached] now provide a powerful platform for the ornamental-flower industry to translate this information to other species, increasing the development of new commercial varieties and species in this economically important research field.
Flowers of wild petunias come in diverse shapes and colours. Cultivated petunias are a hybrid between two wild species––the pink-flowered Petunia inflata and the white-flowered Petunia axillaris. Authors sequenced both of these genomes, and generated transcriptomic data (which detail all the messenger RNA molecules in a cell) from three unrelated cultivated P. hybrida lines. These results provide a superb resource for analyzing not only the genes that confer particular Petunia characteristics, but also the genomics of hybrid formation and maintenance.
Petunia genome assemblies include 91.3% and 90.2% coverage of their diploid genomes (1.4 Gb; 2n = 14) containing 32,928 and 36,697 protein-coding genes, respectively. The genomes reveal that the Petunia lineage has experienced at least two rounds of hexaploidization: the older gamma event, which is shared with most Eudicots, and a more recent Solanaceae event that is shared with tomato and other solanaceous species. Transcription factors involved in the shift from bee to moth pollination reside in particularly dynamic regions of the genome, which may have been key to the remarkable diversity of floral color patterns and pollination systems. These high-quality genome sequences will enhance the value of Petunia as a model system for research on unique biological phenomena such as small RNAs, symbiosis, self-incompatibility and circadian rhythm
Nature Plants June 2o16; 2: 1–9 [main article] and Nature 16 June 2016; 534: 328–329 [News’n’Views]