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Plant‐plant interaction is ubiquitous in nature and can be mutual or
commensal. Some plants have evolved parasitic relation with neighboring
plants during evolution by developing haustorium, a specialized organ that
absorbs nutrient from other plants, causing severe agricultural damage.
Initiation, tissue penetration and vascular connection of haustorium with
host plant involve a serial orders of signal perception, cell fate changes and
host cell wall modification; however, genetic control behind each process is
largely unexplored to data.
To understand the signaling pathways involved in haustorium development, a
genetic screening was conducted in a model root parasitic plant,
Phtheirospermum japonicum. In this seminar, I will introduce several P.
japonicum mutants, that have either altered haustorium number or defects
in host penetration. One of Haustorial Hair Defective (hhds) initially isolated
as root hair and haustorium hair defective mutants (1), showed increased
number of haustoria compared to the wild type. Using whole genome
sequencing, mutation loci is identified in a gene with homologous to
Arabidopsis ABCB4, encoding a plasma membrane protein of ABC transporter
family mediating auxin flux. Further analysis showed that PjABCB4 may
interact with ROS to fine‐control haustorium number. In addition, two
mutants bearing mutations respectively in ethylene receptor (PjETR1) and
ethylene signaling component (PjEIN2) showed impaired cell proliferation
and differentiation at haustorial apical region, resulting in abnormal
haustorium morphology and severe host invasion, indicating the crucial role
of ethylene signaling in host infection by parasitic plant via regulation of
haustorium development (2). Lastly, I will show the structural insight and
origin of haustorium inducing factors (HIFs) from host based on recent
investigation on lignin, a polymer conserved in the land plant (3, 4). These
studies form an important foundation for understanding molecular details
and evolution of plant parasitism.
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