Ever looked at those tiny, green, olive-like capers in your pasta and wondered where they come from? Capers, also called Capparis, is the largest genera in the Capparaceae plant family and consists of around 139 species spread across the tropics. Found in arid habitats, these plants are mostly shrubs, and their flower buds and fruits are widely used as a pickled condiment. 'Liv-52', a herbal medicine usually prescribed to cure liver disorders, is made from a species of capers called Capparis spinosa, which is known to have an excellent therapeutic value.
In a recent study, researchers from Pune's Agharkar Research Institute (ARI) and China's Zhejiang University have explored the genetic traits of two varieties of capers—spinosa and herbacea. While the spinosa variety, which grows at an altitude of 1000m, is used to make 'Liv-52', herbacea, which grows at 3000m, is known to have anti-rheumatic properties. Since it is hard to tell the two varieties apart by just looking at them, the researchers analysed the DNA present in the chloroplasts of the leaves, to do so. The study was published in the journal Phytotaxa and was partially funded by the Science & Engineering Research Board, Department of Science and Technology.
"So far, there are no studies or drugs available based on the herbacea variety. Although anti-rheumatic properties of the plant have been reported from Turkish folk medicine, we need to confirm them and look at the importance of herbacea," says Dr Ritesh Choudhary, a researcher at ARI and the corresponding author of the study.
The researchers collected fresh leaf samples for both the spinosa and herbacea varieties from the Tamhini Ghat in India and Gissar Valley in Tajikistan. They extracted the plastomes—DNA present in the chloroplasts—to sequence them and understand the relationships between the two varieties. They also compared these plastomes with two other plants of the Capparaceae family—Capparis urophylla and Capparis versicolor—to know how closely they are all related.
Capparis spinosa var. spinosa L. (Image Credits: R.K. Choudhary)
The study found that the genetic structure of the plastomes of the two Capparis varieties was similar to those of other plants that grow in arid regions. However, the plastome of herbacea had two genes lesser than that of the spinosa variety. The missing ndhF and ndhG genes code for enzymes that are necessary for photosynthesis. Since the genes were deleted, the DNA segment was also reduced in size, leading to the displacement of other vital genes. This anomaly was absent in the other species studied.
Since the plants at higher altitudes receive a lesser amount of sunlight than those in the tropics, they also have a lower rate of photosynthesis. The researchers hypothesised that the two deleted genes in herbacea were not very crucial for photosynthesis in these plants. The same genes are also missing in plants like conifers found in the temperate regions, and in bladderworts, an aquatic plant. This observation indicates that the lack of the two genes is a phenomenon in plants that are exposed to low sunlight. It is also the first-ever observation of a non-functional gene in the Capparis family.
The findings of the study, which is the first-ever attempt at exploring the plastome DNA sequence, also helped in the process of DNA barcoding. It is a method of using short segments of DNA to identify a particular species of plant. Using the same dataset, the researchers identified several spacer regions (where genes do not code for a protein) and one gene as potential barcodes for the genus Capparis. The development of DNA barcodes could help in the identification of the different Capparis taxa and further help in exploring the various properties found in each one of them.
As the next step in this research, Mr Satish Maurya, a PhD scholar at ARI, wishes to explore the medicinal properties of the herbacea variety. The researchers also plan to work on its genetic and chemical composition, which may reveal novel features of capers.
This article has been run past the researchers, whose work is covered, to ensure accuracy.