Haustorium Inducing Factors for Parasitic Orobanchaceae

Abstract

Parasitic plants in the Orobanchaceae family include devastating weed species, such as Striga , Orobanche , and Phelipanche , which infest important crops and cause economic losses of over a billion US dollars worldwide, yet the molecular and cellular processes responsible for such parasitic relationships remain largely unknown. Parasitic species of the Orobanchaceae family form specialized invasion organs called haustoria on their roots to enable the invasion of host root tissues. The process of forming haustoria can be divided into two steps, prehaustorium formation and haustorium maturation, the processes occurring before and after host attachment, respectively. Prehaustorium formation is provoked by host-derived signal molecules, collectively called haustorium-inducing factors (HIFs). Cell wall-related quinones and phenolics have been known for a long time to induce haustoria in many Orobanchaceae species. Although such phenolics are widely produced in plants, structural specificities exist among these molecules that modulate their competency to induce haustoria in different parasitic plant species. In addition, the plant hormone cytokinins, structurally distinct from phenolic compounds, also trigger prehaustorium formation in Orobanchaceae. Recent findings demonstrate their involvement as rhizopsheric HIFs for Orobanche and Phelipanche species and thus address new activities for cytokinins in haustorium formation in Orobanchaceae, as well as in rhizospheric signaling. This review highlights haustorium-inducing signals in the Orobanchaceae family in the context of their host origin, action mechanisms, and species specificity.

Auxin transport network underlies xylem bridge formation between the hemi-parasitic plantPhtheirospermum japonicumand host Arabidopsis

“…Orobanchaceae parasites can be induced by chemical signals, collectively called haustorium 39 inducing factors (HIFs), a group that includes quinones and phenolic acids (Goyet et al, 2019). Once 40 parasite roots perceive HIFs, cell division and cell expansion are activated, and upon host attachment, 41 apical haustorium cells differentiate into intrusive cells, which have characteristic elongated cell 42 shapes, and function as the main cellular elements in host intrusion (Wakatake et al, 2018).…”

Subtilase activity in the intrusive cells mediates haustorium maturation in parasitic plants

“…Intrusive cells only form at the interphase between parasite and a susceptible host and thus likely participate in the invasion into host tissues and the molecular dialogue between parasite and host (Goyet et al ., 2019). Despite the distinctive nature of intrusive cells, they have not been studied functionally and in detail yet.…”

“…After expression of intrusive cell-specific markers, intrusive cells may invade host tissue, intrusive cells reach the host vasculature, auxin is transported inward towards the root vasculature, and then the XB is formed (Wakatake et al ., 2020). Importantly, treatment with haustorium-inducing factors induces organogenesis of the haustorium in P. japonicum without hosts, but the intrusive cells and XB are not formed in these haustoria (Ishida et al ., 2016, Goyet et al ., 2019). Identification of the unknown host-derived signals required for intrusive-cell specific SBT induction will provide insights into mechanisms of how Orobanchaceae parasites invade the host plants.…”

Management of Infection by Parasitic Weeds: A Review

“…The first stage in haustorium development is initiated upon host detection through chemical and physical signals, which develops an adhesive structure that cements the parasite to the host surface from which the invasive organ subsequently develops [ 7 , 48 , 49 , 50 , 51 ]. Perception of haustorium-inducing signals promotes a cessation of parasite root growth with a rapid swelling.…”