Transcriptome and Cell Type Signature Analysis of Laser-Microdissected Syncytia Induced by the Cyst Nematode Heterodera schachtii in Arabidopsis Roots.

Abstract

Cyst nematodes (CNs) establish a highly specialized feeding structure called a syncytium in host roots by secreting effectors into a selected host cell that reprogram host development programs. The selected host cell undergoes distinct morphological, physiological, and gene expression changes, resulting in the fusion of hundreds of cells to create a novel cell type that does not normally exist in the host. Here, we profiled the transcriptome of the syncytium induced by the beet cyst nematode (BCN) Heterodera schachtii in Arabidopsis roots using laser capture microdissection and RNA-sequencing. Aside from biological processes that are expected to be altered by nematode infection, we also found that genes annotated in nitrate and iron ion signaling and transport related biological processes are significantly overrepresented in genes that are down-regulated by BCN infection, suggesting these ions may play important roles in BCN infection. Comparing the syncytium transcriptome to that of various root cell types showed that it was overrepresented by genes that are enriched in cells marked by ATHB15, a member of HD-ZIP III transcription factor family that is highly expressed in the stem cell organizer of the root vasculature. These results suggest that the syncytium may partially adopt the molecular signature of a stem cell organizer, consistent with our previous hypothesis that BCN uses a stem cell organizer as an intermediate status for syncytium formation.