The insect-protected CTC91087-6 sugarcane event expresses Cry1Ac protein preferentially in leaves and presents compositional equivalence to conventional sugarcane

Abstract

ABSTRACTA Cry1Ac-expressing sugarcane cultivar, CTC91087-6, has been developed by Centro de Tecnologia Canavieira (CTC) to be resistant to the sugarcane borer (Diatraea saccharalis). This genetically modified event was developed using Agrobacterium-mediated transformation and the help of the selectable marker phosphinothricin N-acetyltransferase (PAT) expressed from bar gene. We describe here a detailed characterization of CTC91087-6 event with respect to protein expression, nutritional composition, and assessment of its derived DNA and proteins in raw sugar. Expression of the Cry1Ac and PAT (bar) proteins produced by CTC91087-6 was evaluated in different tissues and at different times during the growing season. The new proteins are preferentially expressed in leaves, are produced at low levels in stalks, and are near the limits of detection in root tissues. The levels of Cry1Ac were much higher than PAT in all evaluated tissues. Furthermore, Cry1Ac levels in CTC91087-6 leaves are stable at various times during sugarcane cultivation cycle, assuring borer control throughout the complete crop cycle. Assessment of CTC91087-6 tissues for key food and feed nutrients as recommended by OECD to assess the safety of new varieties of sugarcane showed compositional equivalence to the conventional counterpart CTC9001 and to other commercial sugarcane varieties used as references. Raw sugar samples produced from CTC91087-6 did not contain DNA corresponding to cry1Ac and bar genes nor DNA specifically derived from CTC91087-6. In a similar way, there is no detection of Cry1Ac and PAT proteins in raw sugar produced from CTC91087-6. Taken together these results show that CTC91087-6 stably expresses Cry1Ac and PAT proteins and is substantially equivalent to the conventional counterpart CTC9001.