Programming plants for self-defence
Each issue of Top Crop Manager can often involve digging into genetics to answer key questions. What makes a plant susceptible to one disease but not another? Why do some pests seem to reproduce at a faster rate after an insecticide application? Genes often hold the key and we rely on researchers to open the door to understanding.
With the rise of gene-editing technologies like CRISPR, these researchers also possess the ability to alter DNA and RNA, transferring the genes responsible for beneficial traits from one organism to another and deleting undesirable traits altogether. Sometimes these alterations lead to surprising results.
Last summer, a team of researchers at Michigan State University (MSU) “knocked out” a defence hormone repressor and a light receptor in a line of Arabidopsis plants (a small flowering species related to mustard). This genetic alteration created a line of plants able to defend themselves against insects while growing faster than their unmodified counterparts.
“This is the growth-defence concept: you promote defence but at the same time you give up growth,” said Gregg Howe, research lead and a professor of biochemistry and molecular biology at MSU, in a press release. “More growth equals less defence, more defence equals less growth. But we’ve done some genetic trickery to get a plant to do both.”
Howe believes this discovery could have implications for food producers, noting the same hormone and light response pathways altered in the Arabidopsis plant are found in major food crops.
Plants can certainly benefit from genetic interventions that accelerate natural evolutionary processes and help them adapt to changing conditions, but they are by no means defenceless without this help.
In 2014, researchers at the University of Missouri discovered Arabidopsis plants can distinguish between different types of vibrations, for example, insect movement versus wind. The team placed caterpillars on the plants and recorded the vibrations they caused while snacking on the leaves. The researchers later played the recording back to one set of plants; a recording of silence was played to a control group. When caterpillars were later allowed to munch on both groups, the ones exposed to the feeding vibrations produced more mustard oils – a turn-off for many caterpillar species.
“What is remarkable is that the plants exposed to different vibrations, including those made by a gentle wind or different insect sounds that share some acoustic features with caterpillar feeding vibrations, did not increase their chemical defences,” said Rex Cocroft, a professor with MSU’s division of biological sciences, in a press release. “This indicates that the plants [can] distinguish feeding vibrations from other environmental vibrations.”
Findings like these have many researchers wondering how they can they apply what they know about a plant’s genetic code to support its existing self-defence abilities. This, coupled with a growing ability to edit genes to produce plants with the most desirable traits, is creating new opportunities for researchers to meet their goals of creating more profitable, plentiful and sustainable crops, which in turn benefits producers.
Top Crop Manager will be closely following these developments and we look forward to sharing the latest discoveries with you in the years ahead.