Knockdown of exportin 1 negatively affects reproduction and maize mosaic virus accumulation in its insect vector Peregrinus maidis

Exportin 1 is a nuclear receptor mediating the nuclear export of proteins and RNA from the nucleus to the cytoplasm. It regulates several processes in the cell, including a general antiviral response and larval progression in Drosophila melanogaster. We evaluated the effect of exportin 1 knockdown on maize mosaic virus (MMV) accumulation and the physiology of the planthopper vector, Peregrinus maidis. MMV is an Alphanucleorhabdovirus that replicates in the nucleus of plant and insect hosts. Exportin 1 knockdown negatively affected MMV accumulation in P. maidis at 12 and 15 days after injection. Likewise, exportin 1 knockdown negatively affected P. maidis reproduction. Analysis of exportin 1 expression in whole bodies of insects across different life stages, nymphs (N1 to N5) and adults (males and females), revealed no difference in gene expression. However, exportin 1 did exhibit tissue specific expression patterns with higher expression in the ovaries compared to the guts of adult females. Adult females with exportin 1 knockdown were significantly heavier and had a larger abdomen compared to controls at four, eight and 12  days after dsRNA injection. Ovary development was significantly inhibited, and mature eggs were not observed in adult females with exportin 1 knockdown. Consistent with a major role of exportin 1 in ovary function and egg production, oviposition and egg hatch in plants was dramatically reduced in dsRNA exportin 1 treated insects. Altogether, these results suggest that exportin 1 is a positive regulator of P. maidis reproduction and it also has proviral activity in the insect vector.