Neuronal calcium sensor 2 is key to moulting and oocyte development in the brown planthopper, Nilaparvata lugens

Intracellular calcium (Ca²⁺ ) is vital for signal transduction in many cellular events. Several Ca²⁺ -binding proteins mediate the transduction of intracellular calcium signals. The EF-hand motifs containing neuronal calcium sensor (NCS) proteins are mainly expressed in the nervous system, where they have important roles in the regulation of a variety of neuronal functions. NCS1 has four EF-hand motifs and well-defined neuronal development functions in a variety of eukaryotes. However, NCS2 has only been identified in invertebrates such as insects and nematodes thus far. The functions of NCS2 remain largely unknown. Here, we identified an orthologous NCS2 in the hemipteran Nilaparvata lugens. Based on qRT-PCR, this gene was found to be primarily expressed in the brain. Knockdown of NCS2 in each nymphal instar by RNA interference led to lethality and caused aggradation and disordered arrangement of lipid droplets in the ovaries and testes of adults, which were associated with the absence of mature oocytes in female ovaries and reduction of spermiation in male adults. Our findings revealed a novel function for NCS2 as a regulator in development and reproduction and suggested that this protein had an important role in modulating lipid droplet remodelling in ovary and testis of N. lugens adults.