Undeniably beautiful in their own right snowdrops promise that spring is on its way! Within these small white flowers there’s also a host of powerful proteins. Some of these proteins allow the plant to emerge and bloom even in frozen soils. Others are being harnessed by humans to treat diseases like Alzheimer’s.
Snowdrops are perennial (living more than two years) and herbaceous (vascular but lacking woody stems) flowering plants. Each plant has two linear leaves and a single bell-shaped flower with six petals – or more accurately tepals – arranged in two circles. Taxonomists have identified just over 20 distinct snowdrop species. All belong to the genus Galanthus.
Snowdrops bloom in late January, February, or March – depending on the specific location and how cold a winter it is. Their incredibly early appearance requires that they sometimes grow in semi-frozen soil and withstand multiple snowfalls. To accomplish these feats snowdrops store an incredible amount of energy in their bulbs. During the fall they also start prebuilding next seasons’ roots and shoots. Also, snowdrops have a small, simple, and sturdy structure that’s ideal for late winter conditions and leaves with hard tips that can easily break through frozen soil.
Another innovation? Moving petals! The outer segments of the flower move upwards and outwards when temperatures are above 10oC (50oF) so that the flower is more accessible to pollinating insects. Below this temperature, the risk of a snowstorm seems to outweigh the benefits of more visiting pollinators, and the plant has evolved to point its flowers downwards. This phenomenon is called thermotropism.
Finally, snowdrops contain several antifreeze proteins (AFPs) that protect their cells from the potentially deadly effects of large ice crystals. These proteins bind to small ice crystals and inhibit further growth. If you’ve ever seen your favorite clump of snowdrops hunched over one cold day only to find them resurrected the next you have AFPs to thank! For an in-depth look into the biochemistry of antifreeze proteins go to the Protein Data Bank’s Molecule of the Month page. .
Another protein that protects snowdrops is Galanthus nivalis agglutinin (GNA). This time from potential predators. This protein is so effective at this task that scientists have tried to insert this gene into other crops such as rice, tobacco, potato, wheat, and maize – with varying levels of success. GNA is a lectin which means it is a carbohydrate-binding protein that binds to specific sugar groups in other molecules and causes angulation and clumping. In the case of snowdrops, GNA binds to d-mannose sugars in an insect’s midgut causing deadly agglutination. This attack strategy is particularly effective against sucking insects like aphids and leafhoppers – two species that tend to be resistant to the other popular gene insecticide Bt. Because of its insecticide properties, scientists have also examined the anti-fungal, antimicrobial, and antiviral properties of this protein.
One of the most well-studied molecules in snowdrops is galantamine. This molecule was initially isolated in 1956 by the Bulgarian chemist Dimitri Paskov reportedly after observing villagers in the Caucus Mountains rubbing the plant across their foreheads to relieve pain and improve cognitive function. Once isolated, scientists discovered that this molecule could easily pass the blood-brain barrier and that it had acetylcholinesterase-inhibiting properties.
Acetylcholinesterase is an enzyme that breaks down neurotransmitters in the synapses between nerve cells and muscle cells. This is an essential task as a buildup of these neurotransmitters can cause paralysis. Consequently, molecules that attack acetylcholinesterase are considered neurotoxins. However, unlike most acetylcholinesterase inhibitors, the effects of galantamine are short-lived and reversible. Moreover, when taken at a low dose in patients with Alzheimer’s, the effect of galantamine consumption was a decrease in confusion. It’s hypothesized that by partially blocking acetylcholinesterase, galantamine causes the number of neurotransmitters in a person’s nervous system to increase which in turn strengthens remaining nerve signals. Today galantamine is the primary ingredient in the drug Razadyne. While this drug has proved effective in clinical studies it does not reverse the course of Alzheimer’s. Also, galantamine has proven difficult to grow or synthesize in mass quantities. Currently, this has limited the availability and success of the drug although scientists continue to work on new production strategies.
So much is packed into these deceptively simple heralds of spring. Next time you see a snowdrop on a winter’s walk take time to consider its beauty and ingenuity both at the macro and molecular level.