Optimization of dsRNA production from microalgae for spray-induced gene silencing approaches

Spray-induced gene silencing (SIGS) is a species-specific environmentally friendly method inducing defence in plants against viruses, fungi, and insects. Spraying dsRNA molecules directly onto plant tissues induces RNA interference (RNAi) mechanism against pathogen/pest target genes. The synthesis of dsRNA is an expensive process; therefore, we proposed the green microalga Chlamydomonas as dsRNA biofactory. Selected target sequences were cloned into an expression vector with convergent promoters. Different background strains were used to identify those with the highest dsRNA expression level. Finally, we discriminate between the production of ssRNA and dsRNA molecules, since only dsRNA molecules are RNAi inducers. After optimizing the dsRNA production system, we applied it to produce dsRNA against target genes of commercial interest. Among them, genes vital for the survival of D. suzukii, an important pest of fruit crops, were produced, allowing us to set-up a new "green" alternative to chemical insecticides. Our approach aims to offer a cheaper and ‘green’ strategy in the fight against pathogens through RNA interference techniques.