P-284 - Ethylene, mechanical pressures and HIFs facilitate Intrusive Cell Differentiation in a Parasitic Plant, Phtheirospermum japonicum

Parasitic plants in the family Orobanchaceae infect host plants and acquire water and nutrients. Phtheirospermum japonicum is a root hemiparasite used as a model plant of Orobanchaceae. It forms a prehaustorium, a parasitism-specialized organ when a P. japonicum root receives the host-derived haustorium-inducing factors (HIFs). The cells on the prehaustorium tip differentiate into intrusive cells (ICs), and the ICs invade the host roots to reach the host vasculatures. Although ICs are significant for parasitism, the molecular mechanisms of their differentiation remain unclear.

We previously reported that ethylene signaling is necessary for IC differentiation because the P. japonicum ethylene-insensitive2 (ein2) mutant does not differentiate ICs upon host interaction. However, the exogenous ethylene application does not induce IC differentiation, suggesting that ethylene is necessary but not sufficient for IC differentiation. In this study, we showed that mechanical stress together with HIF application induces IC differentiation in vitro. Although treating Ca channel blockers did not inhibit IC differentiation, calcium signaling is unnecessary for mechanical stress-induced IC differentiation. Furthermore, we performed a transcriptome analysis during IC differentiation in wild type and ein2, revealing the genes involved in IC differentiation.