Spatial arrangement of tomato defense molecules affects pest resistance

Research shows that the way a defense molecule is shaped in space determines how well wild tomato plants fight off the tomato leafminer (Phthorimaea absoluta) (85). Published in *Nature Communications*, the study indicates that a plant's defense capability depends on molecular organization rather than just the amount of the substance present (85).

The investigation focused on steroidal glycoalkaloids (SGAs), which are natural chemicals used by plants in the *Solanum* family for protection (85). While common tomato varieties (*Solanum lycopersicum*) mostly use α-tomatine, wild varieties (*Solanum pennellii*) rely more on filotomatine (85). Although these chemicals contain the same sugars, their molecular cores possess different three-dimensional arrangements, a concept known as chirality (85). This means the molecules are mirror images of each other that cannot be perfectly overlapped (85).

Testing through plant studies and artificial diets showed that filotomatine is more effective at deterring the leafminer than α-tomatine (85). Researchers believe this difference occurs because the molecule's shape influences how it interacts with biological targets inside the insect (85). While the specific target has not been found, the effect is likely due to stereospecific recognition, where biological systems distinguish between different spatial shapes (85).

The difference stems from the GAME8 gene, which produces an enzyme for building these glycoalkaloids (85). Wild tomatoes possess two versions: GAME8a, which creates filotomatine, and GAME8b, which creates α-tomatine (85). In contrast, cultivated tomatoes have identical sequences for both genes, resulting in the production of α-tomatine (85).

The study showed that changing just four amino acids within one enzyme can reshape the molecule and make it more toxic to the pest (85). This suggests that gene editing could be used to develop new tomato types that better resist leafminer attacks (85).