Gene discovery for pest resistance in corn: bacterial and insect-gut specific chitinases
2003
Hidalgo, M.P. | Garcia, R.N. | Caldo, C.A. | Laurena, A.C. (Philippines Univ. Los Banos, College, Laguna (Philippines). Inst. of Plant Breeding)
Transgenic plant technology can be a useful tool in the development of resistant crops by introducing novel resistance genes into plant species. To date, two main strategies for the generation of insect-resistant plants have been employed. One approach is to use the entomicidal bacterium Bacillus thuringiensis (Bt) as a source of resistant genes and the other is to deploy other insect-resistant genes present in other organisms. The availability of several genes for insect control will enable the plant breeder to "pyramid" these genes for greater protective efficacy, broader spectrum activity and enhanced durability of insect pest resistance. Since "packages" of different genes will be introduced into crops, the components of such packages will act on different targets within the insect pest, thereby mimicking the multi-mechanistic resistance that occurs in nature. Chitinases are hydrolytic enzymes that can degrade the peritrophic membranes of larval midguts. Genes encoding chitinases could be used for stacking with Bt gene. At least seven isoforms of the chitinase gene were isolated and cloned from a local strain of Serratia marcescens, an enteric insect pathogen. Partial cDNAs corresponding to midgut-specific chitinase were also isolated from larval tissues of corn borer isolated in Los Banos [Laguna, Philippines] by RT-PCR. One of the seven isoforms of the bacterial chitinase gene is already a full-length gene and being characterized prior to stable transformation in corn. Based on sequence analysis, it is homologous to ChiA (a secreted extracellular chitinase)
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