Sugar transporters enable a leaf beetle to accumulate plant defense compounds
Horseradish flea beetle: Protected with the weapons of its food plant. Researchers from Max Planck Institute for Chemical Ecology in collaboration with DynaMo Center elucidate how the insect regulates the accumulation of plant toxins via special transporters.
Yang ZL, Nour-Eldin HH, Hänniger S, Reichelt M, Crocoll C, Seitz F, Vogel H, Beran F
Nature Communications volume 12, Article number: 2658 (2021). Doi:10.1038/s41467-021-22982-8
Many herbivorous insects selectively accumulate plant toxins for defense against predators; however, little is known about the transport processes that enable insects to absorb and store defense compounds in the body. Here, we investigate how a specialist herbivore, the horseradish flea beetle, accumulates glucosinolate defense compounds from Brassicaceae in the hemolymph. Using phylogenetic analyses of coleopteran major facilitator superfamily transporters, we identify a clade of glucosinolate-specific transporters (PaGTRs) belonging to the sugar porter family. PaGTRs are predominantly expressed in the excretory system, the Malpighian tubules. Silencing of PaGTRs leads to elevated glucosinolate excretion, significantly reducing the levels of sequestered glucosinolates in beetles. This suggests that PaGTRs reabsorb glucosinolates from the Malpighian tubule lumen to prevent their loss by excretion. Ramsay assays corroborated the selective retention of glucosinolates by Malpighian tubules of P. armoraciae in situ. Thus, the selective accumulation of plant defense compounds in herbivorous insects can depend on the ability to prevent excretion.
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