Three-dimensional reconstructions of haustoria in two parasitic plant species in the Orobanchaceae

Abstract

Parasitic plants infect other plants by forming haustoria, specialized multicellular organs consisting of several cell types, each of which has unique morphological features and physiological roles associated with parasitism. Understanding the spatial organization of cell types is, therefore, of great importance in elucidating the functions of haustoria. Here, we report a three-dimensional (3-D) reconstruction of haustoria from two Orobanchaceae species, the obligate parasite Striga hermonthica infecting rice (Oryza sativa) and the facultative parasite Phtheirospermum japonicum infecting Arabidopsis (Arabidopsis thaliana). In addition, field-emission scanning electron microscopy observation revealed the presence of various cell types in haustoria. Our images reveal the spatial arrangements of multiple cell types inside haustoria and their interaction with host roots. The 3-D internal structures of haustoria highlight differences between the two parasites, particularly at the xylem connection site with the host. Our study provides cellular and structural insights into haustoria of S. hermonthica and P. japonicum and lays the foundation for understanding haustorium function.

Advances on the Visualization of the Internal Structures of the European Mistletoe: 3D Reconstruction Using Microtomography

“…Such structural and chemical gradients might prevent stress peaks at the interface and, thus, guarantee structural integrity. Masumoto et al (2021) have used stacks of cell-type-labeled microscopic images to create a 3D representation of the haustoria of the obligate parasite Striga hermonthica and the facultative parasite Phtheirospermum japonicum. The advantage of this method is that it can distinguish between individual tissues of the haustorium, based on the cellular segmentation of the layers.…”

The penetration of sunflower root tissues by the parasitic plant Orobanche cumana is intracellular

“…Once germinated, the broomrape radicle grows toward the host root (Krupp et al, 2021) and develops papillae, which adhere to the host root and secrete mucilaginous compounds (Joel & Losner-Goshen, 1994). Subsequently, epidermal cells at the tip of the haustorium, a specific parasitic organ, differentiate into intrusive cells that penetrate the host root (Masumoto et al, 2021). This penetration combines physical pressure and degradation of sunflower root cell walls thanks to pectolytic activity enzymes released by the parasitic plant (Shomer-Ilan, 1993;Losner-Goshen et al, 1998).…”

Genomic signatures of host-specific selection in a parasitic plant

“…Following SL perception and parasite germination, host-derived phenolic compounds induce formation of the haustorium, the specialized multicellular feeding structure used by parasitic plants to infest host tissues (Cui et al, 2018). Intrusive cells of the haustoria invade host tissues to form direct connections with host vasculature (Masumoto et al, 2021). Water, nutrients, and other molecules including mRNA (Kim et al, 2014), small RNA (Shahid et al, 2018), DNA (Yang et al, 2019), and proteins (Liu et al, 2020; Shen et al, 2020) can be directly transferred across haustorial connections.…”