Image-Based Lignin Detection in Nematode-Induced Feeding Sites in <em>Arabidopsis</em> Roots

Cyst and root-knot nematodes are sedentary biotrophic parasites that infect a wide range of plant species, causing significant annual yield and economic losses. Cyst nematodes (genera <i>Heterodera</i> and <i>Globodera</i>) induce specialized feeding structures called syncytia in host plant roots, while root-knot nematodes (<i>Meloidogyne</i> spp.) form galls containing feeding cells known as giant cells. This protocol describes the visualization of lignin in <i>Arabidopsis</i> roots infected by beet cyst nematode <i>H. schachtii</i> and root-knot nematode <i>M. incognita</i> using histochemical staining. We present two distinct approaches for lignin detection: direct staining of root segments containing syncytia and galls and histopathological detection in thin longitudinal sections of the feeding sites. Key features • First approach: Staining of intact roots visualizes lignin in nematode feeding sites and requires only simple specimen preparation and staining solution, with no sectioning needed. • Second approach: Staining of longitudinal sections of feeding sites visualizes cell-specific lignin localization and requires moderate tissue preparation and sectioning. • Both approaches enable specific detection and visualization of lignin in nematode-infected <i>Arabidopsis</i> tissues. Graphical overview.