Advances in understanding insect chitin biosynthesis

Retrotransposon-mediated disruption of a chitin synthase gene confers insect resistance to Bacillus thuringiensis Vip3Aa toxin

“…Locus 3105 encodes a chitin synthase (CHS), which is a membrane-integral glycosyl-transferase that catalyzes chitin biosynthesis by transferring GlcNAc from UDP-GlcNAc to a growing chitin chain [ 34 , 35 ]. Locus 3105 and adjacent 3150 are SfCHS2 and SfCHS1 , respectively ( S2 Fig , previously also called SfCHSB and SfCHSA , respectively [ 36 ]).…”

“…The SfCHS2 protein is a class B chitin synthase [ 36 – 38 ]. Class B chitin synthases occur in gut epithelial cells and produce chitin for the peritrophic matrix, which is important for digestion and protection from pathogens [ 34 , 35 , 39 – 42 ].…”

“…One of the factors determining which resistance alleles are most likely to contribute to field-evolved resistance is whether they cause fitness costs in the absence of Bt proteins [ 59 ], which is especially important in governing the frequency of resistance alleles before pest populations are exposed extensively to a particular Bt protein. Disruption of the normal function of class B chitin synthases, such as SfCHS2, could cause fitness costs because these enzymes produce chitin for the peritrophic matrix, which is important for digestion and protection from pathogens [ 34 , 35 , 41 , 42 ]. Unexpectedly, survival on non-Bt maize was 1.4-fold higher for the Vip3Aa-resistant strain Sfru_R3 than its parent susceptible strain SS, implying a fitness benefit for this trait rather than a cost was associated with resistance to Vip3Aa.…”