Host factors influence the sex of nematodes parasitizing roots of Arabidopsis thaliana
Plant-parasitic cyst nematodes induce hypermetabolic syncytial nurse cells in the roots of their host plants. Syncytia are their only food source. Cyst nematodes are sexually dimorphic, with their differentiation into male or female strongly influenced by host environmental conditions. Under favorable conditions with plenty of nutrients, more females develop, whereas mainly male nematodes develop under adverse conditions such as in resistant plants. Here, we developed and validated a method to predict the sex of beet cyst nematode (Heterodera schachtii) during the early stages of its parasitism in the host plant Arabidopsis thaliana. We collected root segments containing male-associated syncytia (MAS) or female-associated syncytia (FAS), isolated syncytial cells by laser microdissection, and performed a comparative transcriptome analysis. Genes belonging to categories of defense, nutrient deficiency, and nutrient starvation were overrepresented in MAS as compared to FAS. Conversely, gene categories related to metabolism, modification, and biosynthesis of cell walls were overrepresented in FAS. We used {beta}-glucuronidase (GUS) analysis, qRT-PCR, and loss-of-function mutants to characterize FAS- and MAS-specific candidate genes. Our results demonstrated that various plant-based factors, including immune response, nutrient availability, and structural modifications, influence the sexual fate sex determination of cyst the nematodes.