Biologists want to cost pesticide companies even more money and a new study of the two-spotted spider mite, Tetranychus urticae, may help. exemplifies the limitations of conventional pesticide-based pest management in agriculture and horticulture. T. urticae mites infest a wide range of crops and fruit trees and can reproduce extremely quickly. They can also develop resistance to chemical pesticides. The new study looked at effects of 18 salivary gland proteins on the resistance of common bean leaves to T. urticae and identified two new tetranins — Tet3 and Tet4 — that appear to reduce the reproduction of spider mites on the plants.
Credit: Gen-ichiro Arimura from Tokyo University of Science, Japan
Using genetic engineering plus molecular and biochemical methods, the team uncovered the roles of Tet3 and Tet4 in the complex interactions between T. urticae and its host plants. Interestingly, they found that the expression of Tet3 and Tet4 varies greatly depending on which plant the mites fed on. Mites feeding on common beans, their preferred host, had significantly higher levels of Tet3 and Tet4 expression than those on cucumbers, a less preferred option.
Plants exposed to mites with higher expression of Tet3 and Tet4 exhibited stronger defense responses, including increased calcium-ion influx, higher generation of reactive oxygen species, and elevated expression of a defensive gene named PR1. The individual application of Tet3 and Tet4 to plants had different effects on plant defense responses, highlighting the specificity of each elicitor’s role.
Tetranins act as crucial links in these complex systems so from an agricultural perspective, tetranins and similar elicitors offer potential for crop improvement.
“Taken together, our findings show that these tetranins respond to variable host cues that may optimize herbivore fitness by altering the anti-mite response of the host plant,” says Professor Gen-ichiro Arimura from Tokyo University of Science.
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