Cry1Ab/Ac proteins released from subspecies of Bacillus thuringiensis (Bt) and transgenic Bt-rice in different paddy soils

ABSTRACT

As Bacillus thuringiensis (Bt) are entomopathogenic bacteria for use as biological insecticide and serve as a main source for genetically modified crops, it is imperative to investigate fate of Bt-toxins (Cry-proteins) released in soil. Four differently textured paddy soils, i.e. sandy loam, loam, silt loam and silty clay, were selected to investigate production and release of Cry-proteins by two Bt-strains (subspecies thuringiensis and kurstaki) and by transgenic Bt-rice (cultivar TT51-1). After amended with Cry-proteins, soil can adsorb proteins while sorption rate was variable among different paddy soils, with the highest amount of Cry-proteins in the silty clay soil. During the period of incubation with Bt-strains, the silty clay soil showed significant accumulation of Cry-proteins. Additionally, level of Cry-protein production was different between two Bt-strains. Inactivation of indigenous microorganisms in the soil samples led to slightly higher production of Cry-proteins by Bt-strains in all four soil types. Cry-proteins were released via root exudates of transgenic Bt-rice in sterile hydroponic culture and in non-sterile soils throughout the growth of plants. Protein release significantly varied among different paddy soils, up to 34.9 ng Cry-proteins g⁻¹ soil in clayey soil. It indicates differently textured paddy soils reflect variable sorption, persistence, and accumulation of Cry-proteins.

KEYWORDS:

• Bacillus thuringiensis
• Bt-rice
• Cry1Ab/Ac proteins
• paddy soil
• soil texture

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Material

Supplementary data for this article can be accessed here.

Additional information

Funding

This work was supported by the Deutscher Akademischer Austauschdienst [A/10/95027].