An Everyday DNA blog article
Written by: Sarah Sharman, PhD
Illustrated by: Cathleen Shaw
As I walked through my garden this morning, inspecting the brown, drab beds of late winter, I was thrilled to spot the first signs of life—my lilies pushing up fresh green shoots. I love this time of year when spring awakens and bursts into a dazzling display of colors and shapes.
It always amazes me how diverse flowers can be. Their variety seems endless, from the delicate petals of a violet to the bold, structured bloom of a tulip. But what drives this incredible floral diversity? The answer lies in their genetics—a blueprint that shapes every petal, hue, and pattern. In this post, we’ll explore the science behind flower diversity, uncovering the pigments, genes, and evolutionary forces that create the stunning displays we see each spring.
A Kaleidoscope of Flowers: Why Color and Shape Matter
Have you ever stopped to really look at the sheer variety of flowers in a garden or the cut flower section of your supermarket? It’s remarkable. Flowers display an incredible range of forms, from the trumpet-like bloom of a lily to the intricate disk of a sunflower. Some are delicate, like a forget-me-not, while others demand attention—such as Rafflesia, the world’s largest flower.
It’s not just shape, either–color explodes in every imaginable hue. You see the deep, velvety reds of a rose, the sunny yellows of a daffodil, and even the rare, almost mystical blues of a Himalayan poppy. And size? We’ve already mentioned the Rafflesia, but consider the tiny blossoms of a thyme plant, which contrast sharply with the plant’s overall bulk.
So, why all this variety? Turns out, it’s all about communication. Flowers have a crucial job: to attract pollinators. Color and shape function as a vibrant language, calling out to bees, butterflies, hummingbirds, and other crucial pollinators.
Pollinators are the backbone of healthy ecosystems, ensuring that countless plant species reproduce. By carrying pollen between flowers, they enable the creation of seeds and fruits. Without them, entire ecosystems—including the animals that rely on these plants—would be at risk.
Flowers evolve specific traits to attract their ideal pollinators. A red, tubular bloom is like a neon sign for hummingbirds, while a yellow, daisy-like shape provides the perfect landing pad for a pollen-hungry bee. It’s a beautifully complex system where every color and every curve has a purpose.
Flower patterns play a huge role too. Many flowers have nectar guides – lines, spots, or other markings that lead pollinators to the pollen or nectar. Some of these patterns are only visible in the UV spectrum, like secret messages only the pollinators can read. These patterns help pollinators orient themselves correctly, ensuring they get a good dose of pollen and nectar, and in turn, help the flower get pollinated. This relationship between flowers and pollinators has helped shape the amazing variety of blooms we see today, each one reflecting millions of years of evolution in action.
Genetics of Flower Color: Painting with Pigments
While pollinators play a role in shaping flower diversity, the real blueprint lies within the flower’s DNA. Just like how our genes determine our hair and eye color, plant genes dictate the colors and shapes of their flowers. It’s a complex process, with genes acting like tiny architects, building each flower according to very specific instructions.
Let’s start with color. How do flowers get their vibrant hues? It’s all about pigment molecules. Pigments act as a flower’s palette, with anthocyanin pigments producing reds, purples, and blues, while carotenoid pigments create yellows and oranges. Genes control pigment production through enzymes, which act like molecular chemists—assembling the compounds that create vivid reds, purples, and golds.
But it’s not just about having the pigments; it’s about controlling them. This is where another genetic element comes into play. Transcription factors act like supervisors and control when and where the enzymes work. They determine the levels of pigments, when they’re produced, and where they’re deposited in the flower. For example, a gene might tell a flower to produce a lot of anthocyanins in its petals, resulting in a deep purple color. Or, a different set of genes might limit pigment production, leading to a pale, pastel shade. It’s an intricate system of checks and balances, all orchestrated by the plant’s genetic code.
Like color, shape is also determined by genes. These genes control everything from cell division and expansion to the development of floral organs like petals, sepals, stamens, and pistils. Imagine genes as tiny sculptors, carefully shaping each part of the flower. Some genes might tell cells to divide rapidly, creating a large, showy petal. Others might control the direction of cell expansion, leading to a curved or elongated shape. And just like with color, these processes are tightly regulated, ensuring that each flower develops its characteristic form. It’s a delicate dance of genes and cellular processes, all working together to create the stunning diversity of floral shapes we see around us.
Unraveling the Dahlia’s Secrets
Dahlias, beloved for their staggering variety of colors and floral forms, are ideal for studying flower genetics. However, their genome has long presented a challenge due to its complexity. Recent research by the Harkess lab at HudsonAlpha Institute for Biotechnology, supported by the American Dahlia Society, has made significant strides in unraveling these genetic mysteries.
In an exciting milestone, HudsonAlpha Faculty Investigator Alex Harkess, PhD, and his lab, led by graduate student Zach Meharg, have now completed the first-ever high-quality genome assembly of the dahlia. This key achievement will serve as a crucial resource for future genetic studies.
One surprising discovery they made is that cultivated dahlias may actually be tetraploid (four sets of chromosomes) rather than octoploid (eight sets), as was long believed. This finding could have significant implications for breeding strategies and evolutionary studies, though additional genome analysis across different dahlia varieties will help confirm these insights.
Beyond decoding the genome, the team is also mapping the dahlia’s family tree. They collected samples from hundreds of dahlias at an American Dahlia Society meeting and have sequenced nearly 200 Dahlia species so far, uncovering new insights into how different varieties are related. Early results confirm many previously theorized connections, providing a clearer picture of how cultivated dahlias evolved. Zach is now working to identify the likely ancestral species that gave rise to today’s diverse dahlia varieties—research that could reveal the origins of some of the most striking floral traits we see today.
Looking ahead, the team is focusing on pinpointing the genes responsible for key floral traits such as petal shape, color, and structure. By identifying the genes that shape these stunning blooms, researchers hope to establish a molecular-assisted breeding program, allowing breeders to select desirable floral traits with greater precision and efficiency.
Unlocking the genetic blueprint of the dahlia is about more than just understanding a single flower—it provides broader insight into how floral diversity evolves, how plant genomes adapt, and how we can harness genetic information to improve breeding programs. Whether for gardening enthusiasts seeking vibrant new dahlia varieties or scientists studying plant evolution, this research represents an exciting step forward in our understanding of flower genetics.
