RNAi-mediated silencing of MSH1 and HSI2 regulates microcystin stress tolerance in tobacco

Microcystins (MCs) predominantly produced by bloom-forming freshwater cyanobacteria are known to affect a number of processes in plants, and their presence in water used for irrigation may exert severe negative effects on the growth and development of plants. In this study, one MSH1 RNAi suppression line and two HSI2 RNAi lines of tobacco ( Nicotiana tabacum ) were constructed and validated by PCR and qRT-PCR, to investigate the effect of RNA interference on microcystin stress response in plants. Plant tissue culture assay on RNAi suppression lines of tobacco showed that MSH1 RNAi and HSI2 RNAi inhibited the growth and proliferation of transgenic tobacco shoots in vitro. After exposure to MC-LR, the mortality of MSH1 RNAi and HSI2 RNAi transgenic shoots was significantly lower than wild-type (WT) shoots. Based on the growth and proliferation, the MSH1 RNAi transgenic shoots showed significantly higher tolerance to MC-LR than WT, and the effect of MSH1 RNAi on improving tolerance was better than that of HSI2 RNAi. These findings implicate MSH1 as a negative regulator of microcystin stress response in tobacco, and suggest that RNAi-based genetical modification may enhance the tolerance of plants to microcystin.