Enhancement of Bacillus thuringiensis Cry1 Ac and Cry1 Ca toxicity against Spodoptera exigua (Hubner) by suppression of a chitin synthase B gene in midgut

The chitin synthase B (CHS-B) gene was cloned from midgut of Spodoptera exigua (SeCHS-B). SeCHS-B contains an open reading frame of 4572 nucleotides, encoding a protein of 1523 amino acids with a predicted molecular mass of approximately 174.6 kDa. The SeCHS-B mRNA was expressed in all developmental stages and specifically in the midgut tissue by qRT-PCR analysis. Expression of SeCHS-B gene was suppressed by feeding double-stranded RNA (dsCHS-B, 400 ng/larva) in the third and fifth instar larvae of S. exigua. Suppression of the SeCHS-B gene expression significantly increased 20% and 25% of mortality on pupation and adult emergence of S. exigua. Also, feeding of dsCHS-B significantly enhanced Cry toxin toxicity to third instar larvae as 34% in 10 mu g Cry1 Ac and 29% in 0.8 mu g Cry1 Ca at 6 days after treatment. These results suggest that the SeCHS-B gene plays an important role in development of S. exigua and RNA interference may apply to effective pest control with B. thuringiensis. (C) 2017 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Published by Elsevier B.V. All rights reserved.