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Science Square (Issue 104)
Mar 1, 2015

Plants Tricked Into Drought Tolerance

Agrochemical control of plant water use via engineered abscisic acid receptors
Park et al. Nature, February 2015.

A recent breakthrough study reported that scientists successfully engineered drought-tolerant plants by adding a new piece of DNA to their genomes. Crops and many types of plants are increasingly challenged by hostile environmental conditions such as globally warming temperatures and diminishing water sources. Plants have very small openings called “stomata” that let carbon dioxide in and oxygen out. Each stoma is surrounded by two guard cells that control opening and closing using osmotic pressure. During daytime, the stomata lets plants allow carbon dioxide in and oxygen out. Since the air around the leaves is often drier than inside, water molecules also move out through the stomata – a process called transpiration. Under the stress of drought, plants produce a hormone called abscisic acid (ABA). When ABA is released, it makes guard cells close the stomata and in turn keeps the plant from losing the water. Scientists previously thought that if they could spray ABA on a whole field, plants would survive a drought. However, since ABA is very expensive and highly sensitive to light, this strategy never became an option. Then, scientists decided to take the commonly used fungicide mandipropamid and genetically engineered the plants to respond to mandipropamid as if it were ABA. By adding a new piece of DNA into genomes, plants ended up having slightly different ABA receptors, which can be efficiently activated by mandipropamid.  Researchers tried this approach on two different plants: tomatoes and Arabidopsis. When mandipropamid was sprayed, genetically engineered plants stopped transpiration, and hence were able to survive for 12 days without water. The next challenge is to test this strategy in real world crops. This approach potentially opens new avenues for crop improvement that could highly benefit a growing world population.

3D Vaccines to Cure the Cancer

Injectable, spontaneously assembling, inorganic scaffolds modulate immune cells in vivo and increase vaccine efficacy
Kim J et al. Nature Biotechnology, December 2014.

Cancer is a devastating disease.  The World Health Organization (WHO) predicts that global cancer incidence rates will grow by nearly 60% to 22 million cases per year over the next two decades. The effective cure for cancer has not been developed yet, mostly due to its ability to escape the body's immune system. Unlike infectious reagents like bacteria and viruses, cancer cells are actually our own cells that are broken and misplaced; they cause trouble as they grow. Scientists have been trying hard to develop vaccines that activate the immune system to recognize tumor cells as foreign and attack them. In a recent study, scientists reported that they designed a “3D vaccine” to effectively provoke the immune system to fight cancer. The 3D vaccine is composed of many microsized, porous silica rods submersed in liquid, where any combination of tumor antigens and immune-stimulating reagents can be loaded into.  Once the 3D vaccine is injected under the skin, it forms into a dime-sized scaffold that creates an "infection-mimicking microenvironment.” The scaffold then attracts the dendritic cells that patrol the body for harmful pathogens. When the scaffold was tested in mice, it showed over a 90% survival rate in animals that would normally die from lymphoma within 25 days. Further analyses in mice showed that the 3D vaccine can recruit, house, and manipulate immune cells to initiate a powerful immune response against cancer. As much as the discovery is promising, one should keep in mind that much more evidence will be required to establish 3D vaccines as a feasible way of combating human cancer.

Smoking Shrinks the Brain

Cigarette smoking and thinning of the brain’s cortex
Karama S et al. Molecular Psychiatry, February 2015.

Smoking is regarded as the single most preventable cause of disease, disability, and death. Past studies strongly linked smoking to cancer and lung diseases. A recent study now shows that smokers have a thinner brain cortex than non-smokers. The cortex is the outer brain layer in which critical cognitive functions such as memory, language, and perception take place. It is well known that the cortex becomes thinner with normal aging and cortical thinning is associated with cognitive decline and dementia. The study found that smoking accelerates this thinning process. Researchers analyzed brain MRI scans of 244 males and 260 females with an average age of 73, around half of whom were former or current smokers. Participants who had given up smoking for the longest time had a thicker cortex compared with those who had given up recently. Researchers cautiously suggest that the cortex might regain some thickness once smokers quit but the recovery is very slow and incomplete. For example, heavy smokers who had quit more than 25 years before still had a thinner cortex.