GLVs can also have antimicrobial effects. Some plants express HPL, the main enzyme of GLV synthesis. The rates of fungal spore growth in HPL over-expressing have been compared with HPL silencing mutants to the wild type plants. Results from the study showed lower rates of fungal growth and higher GLV emissions on the HPL over-expressing mutants, while the HPL silencing mutants showed higher rates of fungal growth and lower GLV emissions, which supports the hypothesis that GLVs have antimicrobial properties.
The antimicrobial properties of GLVs have also been proposed to be part of an evolutionary arms race. During an infection, plants emit GLVs to act as microbial agents, but bacteria and viruses have adapted to use these GLVs to their own benefit. The most common example of this is found in the red raspberry. When the red raspberry plant is infected, the virus influences it to produce more GLVs, which attract the red raspberry aphid. These GLVs cause more aphids to come and to feed on the plant for longer, giving the virus better chances of being ingested and spread more widely. Researchers are now trying to determine whether under infectious conditions plants emit GLVs for their benefit, or if bacteria and viruses induce the release of these compounds for their own benefit. Studies in this area have been inconclusive and contradictory.