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Molecular biology

Guarana DNA

With its 210 chromosomes, the genome of the Amazon region plant provides information about its therapeutic properties


A native species from northern Brazil that has become a synonym for a typically Brazilian soda and an important ingredient of extracts and powders used for various purposes, not all of them scientifically proven, guarana is now starting to be understood in its most hidden aspects: its DNA. Two studies recently published in international journals by members of Realgene (the Legal Amazon Region Genomic Research Network) reveal hitherto unknown aspects of the molecular biology of this plant, which has been grown for hundreds of years by the natives of the Central Amazon region, such as the maués and andirás, as a stimulant. The plant is currently used by modern man in other parts of the country as well, such as in Bahia, the state with the largest guarana production.

The first study, published in the Journal of Plant Research in May of the last year, reveals the existence of 210 chromosomes in the sorbilis variety of Paullinia cupana, the type of guarana analyzed by  researchers. The number called the researchers’ attention, especially when compared to the number found in another seven species of the Paullinia genus, all with 24 chromosomes. “Some colleagues said guarana had so many chromosomes it was practically impossible to count them,” says molecular biologist Spartaco Astolfi-Filho, from the Federal University of Amazonas (Ufam) and Realgene coordinator. However, with the help of Carlos Roberto de Carvalho, from the Federal University of Viçosa (UFV), biologist Danival Vieira de Freitas, from Ufam, the study’s first author, was able to do exactly that. Though not a novel phenomenon, a high number of chromosomes in plants is rare. According to the article, the researchers believe that the guarana domestication process, carried out by the first natives, may have encouraged the selection of the plant with a significant number of chromosomes. Therefore, the natives may have been responsible for the creation and dissemination of the sorbilis variety of P. culpana, currently the type most often grown in Brazil.

The second study was just published last January in Plant Cell Reports and its researchers are still studying this Amazonian “cipó” (Heteropsis spp.) further. Instead of sequencing all the guarana genes, a hard task given the plant genome’s huge size, roughly three times larger than man’s, the researchers chose to look only for the genes activated in the organ of the plant used to produce extracts. The strategy indicated that the fruit of guarana, where its sought-after seeds are found and from which extracts are produced to make beverages and other products, express 2,597 pieces of genes during their ripening process. Among these segments of active genes, technically referred to as express sequence tags (ESTs), there are several segments related to the synthesis of flavonoids, substances with antioxidating potential, and alkaloids, such as caffeine. There are also genes that seem to be important for plant reaction when there is environmental stress, such as droughts, insect attacks and reactions to microorganisms.

Antioxidating flavonoids
In general, the Realgene data is in line with the results of recent studies aimed at confirming the new or old therapeutic properties usually ascribed to guarana. In fact, this was the core objective of the work of sequencing the express genes (in the technical jargon, the “transcriptome”) through the plant’s fruit, throughout its development stages. “We tried to find some sort of molecular base for what was already known about guarana,” explains researcher Paula Ângelo, from Embrapa Amazônia Ocidental, in Manaus, first author of the study published in Plant Cell Reports. In this context, it makes sense, for example, that there is a high level of gene expression that produce enzymes related to caffeine synthesis (99 of the detected ESTs) in the species’ genome. After all, the stimulating substance is found at a concentration of 3% to 6% of the dry weight of the P. cupana seeds, a proportion three times larger than one finds in coffee grains. Perhaps the study’s biggest surprise was the identification of 129 ESTs related to flavonoid metabolism. Many of the possibly beneficial effects for health from the consumption of tea and small doses of red wine – especially cardiovascular benefits – are currently associated with this wide group of natural compounds, which include substances such as tannins, catechin and anthocyanin.

The published articles represent only the beginning, and not the end, of the efforts of Realgene, which brings together scientists from more than ten universities and research institutes from the Amazon and other parts of the country. There is a lot of work left for  members of the genome network, whose projects in the past five years have been granted R$1.5 million in aid by CNPq (Brazil’s National Council for Technological and Scientific Development) and R$300 thousand from Fapeam (the Amazon State Research Support Foundation). They will have to find out whether guarana does in fact produce the proteins that are of greater scientific and commercial interest, and on what level it produces them, as indicated in the article on the transcriptome of the plant’s fruit. They will also try to check the gene activation profile in other types of P. cupana tissue, especially leaves and roots. “At the end of our studies, we would like to further improve the status of guarana as a medicinal plant in the world,” says an optimistic Astolfi-Filho. All this in addition to continuing the sequencing work to map genes expressed in such diverse organisms as the mosquito Anopheles darlingi, the major transmitter of malaria in Brazil, and the “camu-camu” (Myrciaria dubia), a fruit from the Amazon region with 60 times more vitamin C than oranges, and twice as much  as found in acerola.