The Amsterdam petunia germplasm collection: A tool in plant science

Petunia hybrida is a plant model system used by many researchers to investigate a broad range of biological questions. One of the reasons for the success of this organism as a lab model is the existence of numerous mutants, involved in a wide range of processes, and the ever-increasing size of this collection owing to a highly active and efficient transposon system. We report here on the origin of petunia-based research and describe the collection of petunia lines housed in the University of Amsterdam, where many of the existing genotypes are maintained

Insight into the evolution of the Solanaceae from the parental genomes of Petunia hybrida

Petunia hybrida is a popular bedding plant that has a long history as a genetic model system. We report the whole-genome sequencing and assembly of inbred derivatives of its two wild parents, P. axillaris N and P. inflata S6. The current 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 Petunia lineage has experienced at least two rounds of paleohexaploidization, the older gamma hexaploidy event, which is shared with other Eudicots, and the more recent Solanaceae paleohexaploidy event that is shared with tomato and other Solanaceae species. Transcription factors that were targets of selection during 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. The high quality genome sequences will enhance the value of Petunia as a model system for basic and applied research on a variety of unique biological phenomena

anthocyanin1 of Petunia Encodes a Basic Helix-Loop-Helix Protein That Directly Activates Transcription of Structural Anthocyanin Genes

The petunia loci anthocyanin1 (an1), an2, an4, and an11 are required for the transcription of anthocyanin biosynthetic genes in floral organs. The an2 and an11 loci were recently cloned and shown to encode a MYB-domain transcriptional activator and a cytosolic WD40 protein, respectively. Here, we report the isolation of an1 by transposon tagging. an1 encodes a new member of the basic helix-loop-helix family of transcription factors that is functionally and evolutionarily distinct from JAF13, the apparent petunia ortholog of maize RED1 and snapdragon DELILA. We provide genetic evidence that the transcription factors encoded by an1, an2, and an4 operate in an unexpectedly complex regulatory hierarchy. In leaves, ectopic expression of AN2 induces an1 expression, whereas in anthers, an1 expression depends on an4, encoding (or controlling) a MYB protein that is paralogous to AN2. Experiments with transgenic plants expressing a post-translationally controlled AN1–GLUCOCORTICOID RECEPTOR fusion protein indicated that independent of protein synthesis, AN1 directly activates the expression of the dfrA gene encoding the enzyme dihydroflavonol 4-reductase and of Pmyb27 encoding a MYB-domain protein of unknown function

Proteomics of red and white corolla limbs in petunia reveals a novel function of the anthocyanin regulator ANTHOCYANIN1 in determining flower longevity

The Petunia hybrida ANTHOCYANIN1 (AN1) gene encodes a transcription factor that regulates both the expression of genes involved in anthocyanin synthesis and the acidification of the vacuolar lumen in corolla epidermal cells. In this work, the comparison between the red flowers of the R27 line with the white flowers of the isogenic an1 mutant line W225 showed that the AN1 gene has further pleiotropic effects on flavonoid biosynthesis as well as on distant physiological traits. The proteomic profiling showed that the an1 mutation was associated to changes in accumulation of several proteins, affecting both anthocyanin synthesis and primary metabolism. The flavonoid composition study confirmed that the an1 mutation provoked a broad attenuation of the entire flavonoid pathway, probably by indirect biochemical events. Moreover, proteomic changes and variation of biochemical parameters revealed that the an1 mutation induced a delay in the onset of flower senescence in W225, as supported by the enhanced longevity of the W225 flowers in planta and the loss of sensitivity of cut flowers to sugar. This study suggests that AN1 is possibly involved in the perception and/or transduction of ethylene signal during flower senescence

Hyperacidification of Vacuoles by the Combined Action of Two Different P-ATPases in the Tonoplast Determines Flower Color

The acidification of endomembrane compartments is essential for enzyme activities, sorting, trafficking, and trans-membrane transport of various compounds. Vacuoles are mildly acidic inmost plant cells because of the action of V-ATPase and/or pyrophosphatase proton pumps but are hyperacidified in specific cells by mechanisms that remained unclear. Here, we show that the blue petal color of petunia ph mutants is due to a failure to hyperacidify vacuoles. We report that PH1 encodes a P-3B-ATPase, hitherto known as Mg2+ transporters in bacteria only, that resides in the vacuolar membrane (tonoplast). In vivo nuclear magnetic resonance and genetic data show that PH1 is required and, together with the tonoplast H+ P-3A-ATPase PH5, sufficient to hyperacidify vacuoles. PH1 has no H+ transport activity on its own but can physically interact with PH5 and boost PH5 H+ transport activity. Hence, the hyperacidification of vacuoles in petals, and possibly other tissues, relies on a heteromeric P-ATPase pump