Identification of leaf chloroplast-specific promoter to efficiently control of Colorado potato beetle with reduced dsRNA accumulation in potato tubers.

BACKGROUND: By expressing double-stranded RNA (dsRNA) in potato plastids targeting the ß-Actin (ACT) gene of the Colorado potato beetle (CPB), transplastomic plants can trigger the beetle's RNA interference response to kill the CPB larvae. High expression of dsACT driven by rrn16 promoter (Prrn) in the leaf chloroplasts of transplastomic plants confers strong resistance to CPB. However, there are still residual amounts of dsRNA in the tubers, which are unnecessary for CPB control and may raise a potential food exposure issue. RESULTS: In order to reduce dsRNA accumulation in the tubers while maintaining stable resistance to CPB, we selected two promoters (PrbcL and PpsbD) from potato plastid-encoded rbcL and psbD genes and compared their activities with Prrn promoter for dsRNA synthesis in the leaf chloroplasts and tuber amyloplasts. We found that the dsACT accumulation levels in leaves of transplastomic plants St-PrbcL-ACT and St-PpsbD-ACT were significantly reduced when compared to St-Prrn-ACT, but they still maintained high resistance to CPB. By contrast, a few amounts of dsACT were still accumulated in the tubers of St-PrbcL-ACT, whereas no dsACT accumulation in tubers was detectable in St-PpsbD-ACT. CONCLUSION: We identified PpsbD as a useful promoter to reduce dsRNA accumulation in potato tubers while maintaining the high resistance of the potato leaves to CPB. © 2023 Society of Chemical Industry.