How generalist caterpillars neutralize plant toxins that picky relatives can't handle
Wang H, Kong Y, Su X, Shi Y, Zhang J
Plant Defense
Parsnip, celery, parsley, and carrot leaves make furanocoumarins as a defense, and this study shows how a generalist caterpillar dismantles that defense in two steps while its pickier cousin can't.
Some plants load their leaves with poisons to stop caterpillars from eating them. The cotton bollworm beats one of these poisons with a two-step cleanup: one enzyme tweaks the toxin, then another attaches a sugar that makes it far less harmful. Its close cousin, which sticks to fewer plants, doesn't run this cleanup well and gets sick from the same toxin.
Key Findings
The UGT33 enzyme family is the most expanded and diversified UGT lineage in Helicoverpa, and CRISPR-Cas9 knockouts of UGT33 gene clusters in H. armigera showed they are essential for detoxifying the furanocoumarins xanthotoxin and imperatorin.
The P450 enzyme CYP6AE19 converts xanthotoxin into xanthotoxol (O-dealkylation) or 5-hydroxyxanthotoxin (aromatic hydroxylation), and UGT33 enzymes then glycosylate these into less-toxic glucosides.
In the oligophagous H. assulta, weaker CYP6AE19-UGT33 coordination was associated with reduced xanthotoxin detoxification and high sensitivity, linking the pathway to differences in host plant breadth.
chevron_right Technical Summary
Cotton bollworm caterpillars survive plant toxins called furanocoumarins by using a two-step chemical cleanup: one enzyme modifies the toxin, then a second family of enzymes attaches a sugar to make it harmless. A close relative that eats fewer plants lacks this teamwork and is far more sensitive, which helps explain why some caterpillars eat almost anything and others are picky.
Abstract Preview
Original paper
Coordinated P450-UGT detoxification contributes to furanocoumarin tolerance associated with host plant range divergence in Helicoverpa.
Plants and herbivorous insects are engaged in a continuous evolutionary arms race driven by chemical defences and counter-defences. How insects integrate distinct detoxification systems to overcome...
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