Can we harness a plant’s ability to synthesize medicinal compounds?

Can we harness a plant's ability to synthesize medicinal compounds?
A plate showing Senna tora, also called Cassia tora. Credit: From Flora De Filipinas by Francisco Manuel Blanco, in the U.S. public domain.

Anthraquinones are a class of naturally occurring compounds prized for their medicinal properties, as well as for other applications, including ecologically friendly dyes. Despite wide interest, the mechanism by which plants produce them has remained shrouded in mystery until now.


New work from an international team of scientists including Carnegie’s Sue Rhee reveals a gene responsible for anthraquinone synthesis in plants. Their findings could help scientists cultivate a plant-based mechanism for harvesting these useful compounds in bulk quantities.

Senna tora is a legume with anthraquinone-based medicinal properties that have long been recognized in ancient Chinese and Ayurvedic traditions, including antimicrobial and antiparasitic benefits, as well as diabetes and neurodegenerative disease prevention,” Rhee explained.

Despite its extensive practical applications, genomic studies of Senna have been limited. So, led by Sang-Ho Kang of the Korean National Institute of Agricultural Sciences and Ramesh Prasad Pandey of Sun Moon University and MIT, the research team used an array of sophisticated genetic and biochemical approaches to identify the first known anthranoid-forming enzyme in plants.

“Now that we’ve established the first step of the ladder, we can move quickly to elucidate the full suite of genes involved in the synthesis of anthraquinone,” said lead author Kang.

Once the process by which plants make these important compounds is fully known, this knowledge can be used to engineer a plant to produce high concentrations of anthraquinones that can be used medicinally.

“The same techniques that we use to help improve the yields of agricultural or biofuel crops can also be applied to developing sustainable production methods for plant-based medicines,” Rhee concluded.


Newly discovered enzyme helps make valuable bioactive saponins


More information:
Sang-Ho Kang et al, Genome-enabled discovery of anthraquinone biosynthesis in Senna tora, Nature Communications (2020). DOI: 10.1038/s41467-020-19681-1
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Carnegie Institution for Science

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Scientists harness satellites to track algae growth on Greenland ice sheet

Scientists harness satellites to track algae growth on Greenland ice sheet
Algae growing on the surface of the Greenland ice sheet darkens the surface, hastening summer melting. Here, researchers from Columbia University’s Lamont-Doherty Earth Observatory traverse a heavily affected area. Some of the dark material on the surface could also be dust or other debris. Credit: Kevin Krajick/Earth Institute

Scientists know that the brownish-gray algae that darken the Greenland ice sheet in summer cause the ice to melt faster, but only recently have they measured these blooms in the field, and only at few sites. To measure algal blooms across large regions and understand their effects on melting over time, they are now turning to space.


“Scientists go into the field and sample one or two spots where these blooms occur, but we don’t really know how they change over time or over a large region,” said Shujie Wang, lead author of a recent study showing that satellites can be used to track the growth of ice algae over wide areas.

To measure algae growth, Wang and her colleagues borrowed long-standing methodology used by other scientists to measure algae in the oceans, using satellite observations of water color. Marine algae differ from those on ice, but both kinds contain chlorophyll-a, which has a distinct reflected near-infrared radiation signature that satellite sensors can detect.

Mapping glacier algae over space and time can give researchers insights into how algae affect the reflectivity, or albedo, of the ice surface, said Wang, who conducted the research as a postdoctoral scholar at Columbia University’s Lamont-Doherty Earth Observatory. She is now an assistant professor of geography at Penn State University.

“Albedo is crucial for understanding how ice melts and what will happen in the future to the contribution of Greenland to sea level rise,” said Lamont-Doherty research professor Marco Tedesco, who supervised Wang’s work. “Little is known of the effects of algae on this, and the work by Shujie is pioneering in this regard.”

Light-colored snow and ice have a high albedo, meaning that they reflect most incoming solar radiation back to the atmosphere. But when algae accumulate, they darken the surface; this causes it to absorb more radiation, warming the ice and accelerating surface melt.

Scientists harness satellites to track algae growth on Greenland ice sheet
Study coauthor Marco Tedesco (right) measuring the reflectivity of the glacial surface. Such on-the-ground measurements are combined with satellite observations to study algae growth. Credit: Kevin Krajick/Earth Institute

The researchers used data from the Medium Resolution Imaging Spectrometer (MERIS) on the European Space Agency’s Envisat satellite to quantify algal blooms in southwestern Greenland from 2004 to 2011. They compared the data to measurements taken in the field and by NASA’s Moderate Resolution Imaging Spectrometer (MODIS), which measures surface albedo.

They found that chlorophyll-a signatures captured by MERIS matched field data, confirming that researchers can use ocean-color satellite data to measure algal growth and see how it changes over the summer. The same held true for the albedo changes measured by MODIS.

“We came up with a rough estimate that if algae growth doubles, then albedo decreases between 2 percent to 4

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