Strigolactone, reactive oxygen species, abscisic acid, and miR399 pathway in tobacco host plant regulate growth of parasitizing broomrape Phelipanche aegyptiaca during nitrogen or phosphorous stress

BACKGROUND: The broomrape Phelipanche aegyptiaca (Orobanchaceae) is a root holoparasitic plant that acquires carbon (C), nitrogen (N) and phosphorus (P) from host plants. When the host plant suffers from nutrient deficiency, how broomrape responds and the underlying mechanisms remain to be elucidated. RESULTS: Here, using tobacco (Nicotiana tabacum) and P. aegyptiaca as a parasitization system, we show that under the full nutrient, N-, or P-depleted conditions, broomrape parasitism resulted in increased levels of resources (C, N, and P) in the belowground parts (root and broomrape) of the parasitized plants, compared with the roots of non-parasitized plants. By providing the parasitization systems with different N and P levels, we found that broomrape growth is associated with that of the host root. Genetic and transcriptomic analysis indicated that under the N or P stress conditions, the strigolactone, reactive oxygen species, abscisic acid, and miR399 pathway in the tobacco host positively regulate the transcriptome response and growth of broomrape, suggesting that some certain systemic signals controlled by these pathways through together or parting form are transferred from host to broomrape and modulate broomrape physiology. CONCLUSIONS: This study expands our understanding of the nutrient stress physiology of parasitization systems and highlights the roles of these host signaling pathways during the communications between hosts and parasites under nutrient stresses.