Microscopic invertebrates show drought-resistant benefits

  • 8 January 2016, Friday

Source: InterAksyon
4 Jan 2016

MANILA - The key to the development of drought-resistant crops does not all lie in organic farming, but also in the workings of a class of microscopic invertebrates known as water bears or moss piglets, or tardigrades.

tardigrades, with scientific name Milnesium tardigradum, survive under the most extreme climatic conditions, including prolonged desiccation and near 100 percent water loss, freezing and boiling temperatures, intense ionizing radiation, and the vacuum of outer space, reports Bec Crew of Science Alert in an article published on January 3, 2016.

To impart the same attributes on crops, plant breeders are resorting to emulating the system developed by tardigrades to protect themselves from the loss of water, which involves the production of a type of "bioglass" that keep proteins and molecules intact until they are rehydrated back to life.

The proteins that produce the glass could be introduced to various food crops to arm them with the drought-resistant capability of the tardigrades, but the possibility that such crops could be tested in the Philippines is practically nil, owing a Supreme Court (SC) decision banning tests on biotech crops and preventing their importation into the Philippines.

Drought-resistant crops are crucial to food security in the Philippines and the Association of Southeast Asian Nations (Asean), Dr. Paul S. Teng of Singapore said in an address on food security at the Southeast Asian Regional Center for Graduate Study and Research in Agriculture (Searca) late last year.

Searca has supported research into maximizing the production of root crops to boost food security in Asean.

The crucial finding about tardigrades was revealed in September 2015, when researchers at the University of Chicago announced they discovered a new type of glass produced by the invertebrates during desiccation, or the period when they lose water.

This bioglass could conceivably protect crops during prolonged drought by saving water for use during the period of extreme dryness, a genetic characteristic of pineapple, which has a circadian clock and prevents the escape of moisture during the night.

By keeping water in their cells through bioglass, scientists said tardigrades can assure their survival.

"When you remove the water, they very quickly coat themselves in large amounts of glassy molecules. That’s how they stay in this state of suspended animation," lead researcher and molecular engineer Juan de Pablo said.

Buoyed by the discovery, biologist Thomas Boothby of the University of North Carolina (UNC) notes researchers are now closer to understanding the secret of tardigrade bioglass.

In the annual meeting of the American Society for Cell Biology last week, Boothby and his colleagues revealed they have identified tardigrade-specific genes that code for specialized proteins called intrinsically disordered proteins (IDPs) that are observed to be responsible for the production of tardigrade glass.

IDPs are shapeless and highly flexible under normal conditions, but their production intensifies during extreme drying and they rearrange themselves into solid biological glasses, Boothby stressed.

"These newly formed IDP glass structures target specific proteins, molecules, and other essential cell parts when the tardigrade starts losing water, and enclose them in stiff, protective envelopes so they don't fall apart during the desiccation process," Science Alert noted.

Once tardigrade becomes wet, the bioglass melts and the IDPs return to their floppy, random state.

Boothby and his colleagues tested the survival mechanism by engineering tardigrades with lower levels of IDPs, and discovered that, while these tardigrades were less able to withstand desiccation, they remained unaffected by other stresses such as extreme cold.

"Interestingly, these genes do not appear to be essential for general survival or for surviving other stresses," they reported.

The researchers then tested the IDPs by expressing them in human epithelial cells (HeLa), and noted, "we found that when expressed in HeLa cells, desiccation induced a relocalization of these IDPs, which under hydrated conditions appeared diffuse throughout the cell cytoplasm, to specific cytoplasmic organelles – suggesting that individual proteins are targeted to different parts of cells, perhaps protecting specific cellular compartments. We found in vitro these proteins formed biological glasses when dried."

The Boothby team engineered yeast and bacteria to produce tardigrade glass proteins and found that they, too, survived better when put under extremely dry conditions.

Thus, the team argued that bioglass could be a key to engineering drought-resistant crops.

Boothby and his colleagues say they could protect certain enzymes from drying out and can seriously cut the cost of storing vaccines.

"Around 80 percent of the costs of vaccination programs in developing countries comes from having to keep vaccines cold," they reported.

As Tina Hesman Saey at Science News explains, the researchers have shown that tardigrade glass can also protect enzymes from drying out in experiments: "The enzyme [lactate dehydrogenase] loses its activity when dried out. But when the researchers mixed the enzyme with the glass proteins before drying, the enzyme bounced back to normal activity when rehydrated. Mixing in water bear proteins after drying didn't help, indicating that the glass proteins need to encase other molecules to protect them."