Current understanding of the role of the cell wall in Cuscuta parasitism

The plant cell wall (CW) plays a crucial role in many aspects of parasitism by the obligate stem parasite, Cuscuta. Cuscuta parasitism begins with tight coiling around the host stem by the strong tensile force of the thickened inner cell wall layers, and attachment to the host surface using secretory CW components. Subsequently, invasion of a feeding structure called the haustorium is facilitated by degradation and modification of host CWs. Furthermore, haustoria-derived search hyphae transdifferentiate into tracheary elements of the secondary cell walls (SCW). SCW provides mechanical strength and hydrophobicity to the tracheary element. Therefore, Cuscuta can draw fluids from the host through the tracheary element. Thus, the parasitic processes in Cuscuta are closely linked to their CW structures and functions. In this review, we comprehensively summarise the role of the CW in each parasitic process of Cuscuta and provide details on the current understanding of Cuscuta parasitism.