The unique behavior of a popular plant in botany labs worldwide that can "hijack" other genes has been explained. The single remarkable mutation that makes the plant so useful could be the key to the efficient growing of food on Mars.
Nicotiana benthamiana, called pitjuri in some Australian Indigenous languages, is one of the world's most used model plants. "You can squirt it with bacteria and it will express [the bacteria's] genes as if they are its own," Professor Peter Waterhouse of Queensland University of Technology (QUT) in Australia told IFLScience. "It allows you to do something in three days that would take months with other methods."
The thousands of laboratories around the world that use pitjuri rely on lab-grown seeds. These trace their ancestry back to samples collected in Australia in 1939 and sent to America.
Despite pitjuri's DNA having been sequenced, the genetic basis of its remarkable properties has been debated in scientific literature. Waterhouse studied seeds from the plant collected across wide areas of Australia and found that most behaved like every other plant species known, not like the laboratory versions. However, seeds collected from northern South Australia produced plants equally expressive of introduced DNA.
When Waterhouse and Dr Julia Bally, also of QUT, compared the two types of pitjuri they found the difference. The lab version doesn't have an immune system, causing Waterhouse to compare it to a “nude mouse", the name given to mice with a mutation that greatly inhibits their immune system. The energy most plants put into defending themselves goes into growing 50 percent bigger seeds.
For most plants, as for humans, the lack of a defense against pathogens would be fatal. However, pitjuri lives in desert regions where nothing grows for years, followed by brief bursts of life after rare rains, similar to what is now occurring in the Atacama desert. Few pathogens survive the long dry periods, but there is a great incentive to grow fast when good times come.
"The plant has worked out how to fight drought – its number one predator – in order to survive through generations," Waterhouse said in a statement.
In Nature Plants, Waterhouse and Bally traced the lack of immunity to a single disruptive insertion in the gene Rdr1, occurring 750,000 years ago. The mutation is recessive, so when “nude” plants are crossed with normal versions the offspring are resistant.
Waterhouse told IFLScience that this has stimulated further changes. Immune pitjuri is fertilized by insects, using large flowers to attract pollinators. The desert version needs to avoid cross-fertilization if it is to pass on its party trick, so its flowers are smaller, making them less attractive to insects and fertilization more likely to occur with nearby flowers of the same type.
Waterhouse is interested to see whether nude versions of other plants would also produce more seeds. While useless as crops on Earth, plants that don't waste energy on defense systems could grow food much faster and with less water on Mars, provided we can stop plant diseases hitching a ride with future missions. Waterhouse also thinks “nude tomatoes” or “nude soybeans” might be useful in the lab, speeding up research just as N benthamiana has done.
