Abstract

BACKGROUND By expressing double-stranded RNA (dsRNA) in potato plastids targeting the β-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 ds ACT 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 (P rbcL and P psbD ) from potato plastid-encoded rbcL and psbD genes and compared their activities with P rrn promoter for dsRNA synthesis in the leaf chloroplasts and tuber amyloplasts. We found that the ds ACT 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 ds ACT were still accumulated in the tubers of St -PrbcL-ACT, whereas no ds ACT accumulation in tubers was detectable in St -PpsbD-ACT. CONCLUSION We identified P psbD 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.