Why don’t parasitic plants attack their own and closely related species?

October 24, 2025

The world's first elucidation of the “kin-avoidance” mechanism

The joint research group from the Nara Institute of Science and Technology, the RIKEN CSRS, and Kyoto University clarified, for the first time in the world, how parasitic plants avoid parasitizing their own or closely related species at the molecular level.

Parasitic plants are devastating weeds that can cause significant damage to agriculture worldwide, costing more than $1 billion annually. Meanwhile, they curiously don’t parasitize their own or closely related species. The joint research group analyzed a mutant of the model parasite plant Phtheirospermum japonicum and found a sugar-conjugation enzyme involved in a “kin-avoidance” mechanism. This enzyme, UDP -glucosyltransferase 72B1 (UGT72B1), adds sugar to haustorium-inducing factors (HIFs), which signal to start parasitism, and thereby inactivates the parasitizing signal. The mutant, in which this enzyme was disrupted, formed haustoria (a structure for parasitism to intrude into the host plant and connect with its vascular bundles to obtain water and nutrients) triggered by its own metabolite, even when host plants were absent. A further enzyme activity analysis revealed that UGT72B1 in Phtheirospermum japonicum recognizes a broader variety of HIFs than its analogous enzyme in Arabidopsis thaliana. These findings suggest that parasitic plants avoid parasitizing kin species by comprehensively inactivating HIFs produced by themselves. The results of this study have elucidated, for the first time, the molecular-level mechanism of kin avoidance and efficient identification of host plants in parasitic plants. They could lead to a new defense strategy against parasitic weeds.

Original article: Science　doi: 10.1126/science.adx8220; L. Xiang, S. Cui, S. B Saucet, M. Takahashi, S. Inaba, B. Xie, M. Schilder, S. Shimada, M. Cui, Y. Li, M. Watanabe, Y. Tobimatsu, H. J. Bouwmeester, T. Tohge, K. Shirasu, S. Yoshida,; "Glucosylation of endogenous haustorium-inducing factors underpins kin avoidance in parasitic plants".
Contact: Ken Shirasu
GroupDirector
Plant Immunity Research Group