Abstract
Engineered insecticidal δ-toxins protect cotton genotypes against devastating insects but the accumulated amount of toxin
varies during the growth period, generating conflicting results. Here we report varied effects of cry1Ac gene, driven by CaMV
35S promoter, in aerial parts of cotton plant including seed under different growth and environmental regimes. Data is recorded
after every 20 days, starting from 60 to 120 DAS at temperatures 25°C, 35°C, 40°C and 50°C. An increasing trend in the
concentration of δ-toxin in leaves is observed from 60 to 100 DAS and at temperature from 25°C to 40°C, and is decreased at
120 DAS and 50°C. The levels of accumulated toxin are significantly higher in MNH-886 compared to FH-142, irrespective
to temperature and age of the plants, demonstrating that MNH-886 is more stable genotype for transgene expression and for
effective insect control. Interestingly, transprotein is accumulated 28% and 130% higher in seeds (3.6 µg g-1
) than in the leaves
(2.8 µg g-1
) and 15 DAP locules (1.59 µg g-1
); respectively, suggesting that varied expression is due to interaction of 35S
promoter with environmental factors, plant growth and development. Insects Pectinophora gossypiella, Helicoverpa armigera
and Spodoptera litura are serious threats to cotton crop. First two damage bolls whereas later attacks on leaves thereby results
in loss of photosynthetic area on leaves consequently lower the yield. This calls for tissue-specific or inducible engineering of
toxins in cotton for effective control of insects and biosafety of non-target animals and human being since they feed on seedcake
and cotton seed oil respectively.
