A molecular approach to combat spatio-temporal variation in insecticidal gene (<Emphasis Type="Italic">Cry1Ac</Emphasis>) expression in cotton |
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| Authors: | Allah Bakhsh Saima Siddique Tayyab Husnain |
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| Institution: | (1) National Centre of Excellence in Molecular Biology, University of the Punjab, 87 West Canal Bank Road, Thokar Niaz Baig, Lahore, 53700, Pakistan |
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| Abstract: | Spatio-temporal expression of an insecticidal gene (Cry1Ac) in pre existing transgenic lines of transgenic cotton was studied. Seasonal decline in expression of Cry1Ac differed significantly among different cotton lines tested in the field conditions. The leaves of the Bt cotton plants were found to have the highest levels of toxin expression followed by squares, bolls, anthers and petals. Expression
of the gene decreased consistently with the age of plants. Toxin expression in fruiting parts was not enough to confer full
resistance against bollworms. The reduction in efficacy of transgenic cotton plants late in the season was attributed to reduction
in promoter activity. For this purpose, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit (rbcS) promoter was isolated from Gossypium arboreum that was further cloned upstream of an insecticidal gene (Cry1Ac) in expression vector pCAMBIA 1301. A local cotton cultivar NIAB-846 was transformed with Cry1Ac driven by rbcS promoter. The same cotton cultivar was also transformed with Cry1Ac gene driven by 35SCaMV promoter to compare the expression pattern of insecticidal gene under two different promoters. The
results showed that rbcS is an efficient promoter to drive the expression of Cry1Ac gene consistent throughout the life of cotton plant as compared to 35S promoter. The use of tissue specific promoter is also
useful for addressing the biosafety issues as the promoter activity is limited to green parts of plants, hence no gene expression
in roots, cotton seed and other cotton products and by products. |
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