Even more so than coffee, tea is the most popular drink in the world, barring alcohol itself. Its history stretches back thousands of years and across dozens of cultures. The caffeine within and the multiple health benefits from regular consumption have helped continue its popularity to this day. But that popularity includes an ever increasing number of consumers, meaning that production must equally scale-up in size.
One Tea To Rule Them All
The primary source for tea is from the tea flower plant, Camellia sinensis. Other than rare exceptions, every type of tea is made from this single species, with different cultivars of it making up Chinese vs Indian tea types. Colored types of tea, such as green tea vs black tea, has to do with how the plant is processed and not the plant type itself.
Even though there are over a hundred species within the Camellia genus, only the one is used for making tea. The others are largely ornamental, except for Camellia oleifera that’s used to produce tea tree oil.
This isolated species being responsible for such a popular staple is both a good and bad thing. One species means that all of our agricultural focus for tea can be on the one plant and biotech improvements only need to be done to one species. At the same time, any pathogens that emerge to prey upon the plant could wipe out the entire crop worldwide if it is contagious and lethal enough.
For the purposes of this article, a single species means only one genome needs to be analyzed and understood. And that will help to figure out just what makes C. sinensis so special that it can be used to produce such a vast cornucopia of flavors.
Mapping Duplications
Researchers from the Chinese Academy of Sciences and other organizations from around the world worked on sequencing a cultivar of the tea flower plant from southwestern China. This included a full transcriptome and phytochemical set of analyses in order to not only map the genome, but also to connect genes to the flavor molecules that are formed from them.
Out of all the mRNA transcripts, they were able to map 75% of them properly and connect more than 90% of those to their individual producer genes. They found that, in comparison to other commonly sequenced genomes like coffee, potatoes, peppers, and tomatoes, the tea flower plant has the largest genome by several times over and the most amount of repetitive DNA sequences.
It was also discovered that the tea flower appears to have had two instances of polyploidy in the past that resulted in whole genome duplication. The older instance matches up with the same event found in grapes and kiwifruit, indicating it was a shared event prior to their speciation. The other, more recent, event appears to only be shared between four specific Camellia species, including C. sinensis.
Jumping Pathways
One of the things beyond that which seems to contribute to its genome being so humongous is the large number of transposons, also known as jumping genes. Their frequent migration throughout the genome during breeding has resulted in copies of them being strewn across it. The scientists suspect that these duplicates likely helped protect and enhance its abilities to resist pathogens and survive in different climates. Due to one of the major expansions of the genome being recent, it is believed that human cultivation was involved in this process.
A final bit of surprising information revealed from the mapping is the evolution of the biochemical pathway for caffeine within the tea flower. The genes involved indicate that the tea flower and cacao developed the pathway together via a common ancestor, separate from coffee’s development of caffeine. They then later diverged and evolved separately into the cacao and tea flower plants we know today.
With most of the genome now matched and a better understanding of the genes, their transcription outputs, and the resulting metabolites from the active proteins, the researchers will now be focusing on narrowing down what most contributes to the flavors in tea. The genes that are eventually picked out can then be subject to modification and an increase in flavor depth, potentially, along with creating an even wider range of possible flavors should result.
The Tea Must Flow
Since it took them five years to complete putting together the genome, it is expected to take some more time and experimentation before pinpointed genes can be presented for further work.
Improved tea does, however, appear to be right around the corner. Tea drinkers out there, rejoice, the era of an even more multifaceted set of tea options is approaching.
Photo CCs: Camellia sinensis-IMG 3444 from Wikimedia Commons
