Elucidation of a part of the intrusion organ generation mechanism of parasitic plant

July 7, 2016

A key step is local biosynthesis of auxins

Orobanchaceae plants such as Striga spp. (witchweed) are parasitic, sending out a specialized root organ called a haustorium to penetrate the root of host plants and siphon off water as well as nutrients. Striga infestations seriously reduce crop yields and are a major threat to cereal crops. RIKEN CSRS, in collaboration with Pennsylvania State University and the University of Tokyo, developed a model plant from Phtheirospermum japonicum (an Orobanchaceae family plant native to Japan) to identify genes for haustorium development. Researchers carried out a large-scale sequence analysis, focusing on genes related to auxin hormones–in particular YUC3, which encodes YUCCA, a key enzyme for auxin synthesis. They found that YUC3 was specifically expressed in the epidermal cells of the haustorium, and coincided with an increase in endogenous auxin. Analysis of auxin response during haustorium formation indicated an overlap with early-stage YUC3 expression patterns. Reducing YUC3 expression reduced the number of haustoria formed. Conversely, inducing YUC3 expression specifically in the epidermis resulted in the formation of haustoria-like structures. From these results, researchers concluded that YUC3-mediated auxin synthesis in the haustorium plays an important role in haustorium formation.

The present study offers insight into the mechanism driving haustorium formation, which is the first step of the parasitic process. Further elucidating this mechanism will contribute to practical methods preventing agricultural damage by parasitic plants.


Original article
The Plant Cell doi: 10.1105/tpc.16.00310
J. K. Ishida*, T. Wakatake*, S. Yoshida, Y. Takebayashi, H. Kasahara, E. Wafula, C. W. dePamphilis, S. Namba, K. Shirasu (*co-first authors),
"Local auxin biosynthesis mediated by a YUCCA flavin monooxygenase regulates the haustorium development in the parasitic plant Phtheirospermum japonicum".

Ken Shirasu
Group Director
Plant Immunity Research Group